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hi everyone um i'm just going to go

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ahead and say a few things as people are

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making their way to their seats we have

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short 10 minute slots so i thought i'd

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start the introduction just a little bit

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early

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so that we can give everyone their full

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10-minute slots we're trying a slightly

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new format here so everyone has uh 10

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that's my computer so i could hear

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myself talking to myself um so we have

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10 minute slots so if you want to fill

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your your whole 10 minutes um with your

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talk that's fine if you want to leave a

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little bit for questions that's fine too

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we do have one withdrawn the fourth

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talk is withdrawn so we will have a 10

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minute slot there that we can ask

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questions in

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for anyone watching online we have uh in

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the in the vimeo thing there is a

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chat box and i will be monitoring that

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so feel free

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as the speakers are talking go ahead and

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drop your questions in there and then

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when we if we have the opportunity we

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can ask them at the end

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um so

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i think those are kind of all of the the

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technical things um and with that i'd

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like to welcome you all to our session

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on the co-evolution of the geosphere and

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biosphere and we're looking at early

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earth environments and all that that

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entails from the geochemical and

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mineralogical to the organic chemistry

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and

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the biology that goes into that which i

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think is really a testament to how

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truly complex these systems are and i i

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love doing sessions like this because we

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can get this holistic uh overview of

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this so this is our last last portion of

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this session

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we had an online session yesterday that

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you can go check out and is available on

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demand online so you can all go see that

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if you'd like and without further ado

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i'd like to uh invite our first speaker

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to come up and that is nicole zellner

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and

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i thought she was great to start us off

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um because she's talking about uh

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earth's first billion years maybe not so

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hadeen after all so

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thank you shauna

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so

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we all know that lots of interesting

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things were happening in the first

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billion years and i'm going to provide

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somewhat of an overview of some

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different scientific reports from

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different scientific disciplines and i

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invite us all to have a discussion about

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how to reconcile some of these

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conflicting results that have been

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reported

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in particular because i'm coming from

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the impact

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side of these investigations i study

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lunar impact glasses to understand what

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the impact flux is like in the in our

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solar system i'm particularly interested

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in what we know about that impact impact

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flux and whether or not it really

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induced any kind of impact frustration

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or sterilization to the origin of life

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so as a reminder this is a summary that

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shows the four different scenarios that

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we have adopted over the last

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40 50 decades to try to understand what

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that impact flux looks like in the inner

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solar system whether or not it was a

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smooth decline which is what we would

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expect for planetary systems that are

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forming during final accretion and sweep

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up of planetesimals whether or not there

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was something called the cataclysm which

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is now known as the late heavy

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bombardment that may have occurred

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around 3.9 billion years ago and caused

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a bottleneck in what we think might have

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been the origin of life or if it was

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some combination of the of the the two

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and understanding what this impact flux

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is is important because of these really

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interesting biological and geological

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events that we now know were happening

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on the early earth

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including a cool early earth with land

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masses and water around 4.3 to 4.4

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billion years ago

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carbon isotopic evidence for first life

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around 3.9 or 3.85 billion years ago and

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finally uncontested evidence for fossils

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somewhere around 3.5 billion years ago

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and trying to reconcile all these

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different data sets becomes really

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important for understanding the

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conditions of what

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that were occurring on our early earth

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i'd like to remind people that we have

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lots and lots of lunar data both in the

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apollo sample collection and now the

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chinese sample collection as well as

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orbital data from the lunar

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reconnaissance orbiter and other

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spacecraft that are allowing us to have

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more refined and constrained

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measurements of the lunar surface and

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the samples that were collected from the

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surface and on the left hand side of the

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screen here you'll see the relative

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tentative ages that have been assigned

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to the largest lunar impact basins on

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the moon we use the moon as a proxy for

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understanding the impact rate in on the

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earth because the earth has an

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atmosphere plate tectonics and water and

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has erased a lot of the oldest evidence

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for

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impacts the moon on the other hand

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preserves them and so by this large

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range of ages that you can see assigned

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to these nearside impact basins you can

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see that this idea of a lunar cataclysm

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wherein all of these large impact basins

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were proposed to have been formed in a

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very narrow time period probably isn't

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we also now have evidence in the

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terrestrial record for a tailing off of

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impacts over the last uh

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3.2 to 3.4 or so billion years after the

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solar system formed these were

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impact sphero layers that are found in

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some of the oldest terrains in south

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africa and australia that provide

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evidence for a decrease in bombardment

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that was pretty long lived and not a

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sharp cut off

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as you would expect in something like a

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cataclysm

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the grail orbiting spacecraft as well

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measured

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now invisible impact basins on the moon

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basins that we cannot see with the naked

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eye

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that were formed and then eroded over

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four and a half billion years of earth

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moon system history so this spacecraft

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additionally provided evidence for many

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large degraded old basins that provide

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evidence for impacts prior to 3.9

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billion years ago so before that sharp

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spike of the proposed cataclysm would

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have happened

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so again here is uh that summary of the

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four impact scenarios that have been

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proposed and i hope i've convinced you

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that the idea for the cataclysm or

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what's known as a late heavy bombardment

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in its strictest definition

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has pretty much

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been

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replaced by

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potentially a sawtooth pattern or

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something called an early intense

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bombardment or if you average out that

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early intensive environment the smooth

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decline and the smooth decline can

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actually explain the amount of highly

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citrophile elements that we see on the

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surface of the moon we don't need to

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have it delivered all at once by

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something like a cataclysm

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we do know that organic molecules have

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been delivered in prodigious amounts

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particularly in the first billion years

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of solar system history

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uh chris chiba and and others in in over

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40 years ago proposed the delivery of

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organic molecules to be somewhere on the

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order of 10 to the 11 kilograms per year

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and investigators such as

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jennifer blank ella peterson zeta

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martins vanessa mccaffrey myself have

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shown that these organic

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molecules can actually survive impact in

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particular mccaffrey at all showed that

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the glycoaldehyde which is a very simple

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sugar can deliver can be delivered and

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survive impact

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which is an important

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factor when you think about

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glycoaldehyde being necessary for the

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foremost reaction and structure

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synthesis so organic molecules can

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actually survive these very high

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intensely

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high pressure high temperature impact

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events so let's try to reconcile some of

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this evidence then remembering that the

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moon has experienced a smooth decline in

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impacts and that organic molecules can

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actually be delivered intact

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early terrestrial evidence reported by

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john valley and others at the university

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of wisconsin and other locations have

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shown that zircons preserve evidence of

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a cool early earth in the form of land

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masses and water

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potentially suggesting a hydrosphere

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around 4.3 billion years ago

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plate tectonics probably started very

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early on there was a recent report

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by drabin at all that says these plate

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tectonics were probably a global event

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as early as 3.8 billion years ago and so

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what this means is that earth's chemical

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evolution and thermal effects not to

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mention the resupply and supply of

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organic molecules from the interior have

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been largely regulated by these plate

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tectonics throughout most of earth's

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history

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one of the biggest questions that we're

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facing in the origin of life community

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is whether or not there's a reducing

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atmosphere an environment on earth or

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whether it was oxidizing

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biology prefers a reducing atmosphere

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but the geological evidence shows our

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atmosphere was probably oxidizing as

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late as early as 3.9 billion years ago

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so somehow we have to reconcile these

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really important competing ideas

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and finally when when did biogenic

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carbon when did biology actually occur

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on earth elizabeth bell and her group at

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ucla reported

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reported evidence of the presence of

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biogenic carbon in a 4.1 year old

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4.1 billion-year-old zircon and there's

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been multiple studies about isotopic

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carbon uh related to biology being

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present in sediments in some of the

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oldest sediments around the world this

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biogenic carbon proposed biogenic carbon

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has been

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published by multiple different

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investigators in multiple different labs

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we also are starting to push back

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evidence for fossilized biology as well

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some of the earliest marine

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evidence includes these fossilized

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hematite tubes that have been found in

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canada with an age of around 3.8 billion

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years and tara jock itch and her group

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have found

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pterosites in microbial palisade fabric

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which potentially could be indicative of

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terrestrial life by 3.48 billion years

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ago

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so what i've done here now is uh showed

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a

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um but this doesn't um

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sorry let me find the word um

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this doesn't mean that um

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a audience of life in the

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in the

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right so it really doesn't uh

282
00:12:44,310 --> 00:12:42,880
delete that or

283
00:12:46,949 --> 00:12:44,320
it is

284
00:12:49,030 --> 00:12:46,959
um i don't think that would

285
00:12:51,190 --> 00:12:49,040
mean that the low t

286
00:12:53,110 --> 00:12:51,200
oriented of life would be

287
00:12:55,190 --> 00:12:53,120
the most probable because you would have

288
00:12:58,550 --> 00:12:55,200
anyway this

289
00:13:01,269 --> 00:12:58,560
a deep ocean uh volcanoes where

290
00:13:03,110 --> 00:13:01,279
it could happen too sure right i mean we

291
00:13:05,110 --> 00:13:03,120
talk a lot about these um deep ocean

292
00:13:06,389 --> 00:13:05,120
hydrothermal vents um so we think about

293
00:13:07,750 --> 00:13:06,399
a high temperature

294
00:13:09,509 --> 00:13:07,760
environment where those reducing

295
00:13:10,870 --> 00:13:09,519
molecules have been erupted from the

296
00:13:12,949 --> 00:13:10,880
interior of the earth but there

297
00:13:14,710 --> 00:13:12,959
certainly is a temperature gradient

298
00:13:17,269 --> 00:13:14,720
around those hydrothermal vents where

299
00:13:19,509 --> 00:13:17,279
the temperature could get cooler or does

300
00:13:22,230 --> 00:13:19,519
get cooler and molecules could

301
00:13:23,670 --> 00:13:22,240
additionally form in um simple life

302
00:13:28,870 --> 00:13:23,680
could additionally form in those kinds

303
00:13:28,880 --> 00:13:32,949
thank you okay thank you

304
00:13:38,470 --> 00:13:35,430
thank you so much nicole that was an

305
00:13:40,069 --> 00:13:38,480
awesome talk and so next we have up uh

306
00:13:42,069 --> 00:13:40,079
monica fedori and so we're going to

307
00:13:44,150 --> 00:13:42,079
continue talking about

308
00:13:45,590 --> 00:13:44,160
impacts and i'm i'm looking forward to

309
00:13:47,269 --> 00:13:45,600
this one because i think this should be

310
00:13:49,829 --> 00:13:47,279
fun i'm looking forward to all of them

311
00:13:52,790 --> 00:13:49,839
to be clear but um

312
00:13:57,590 --> 00:13:52,800
all right it's taking a second

313
00:13:57,600 --> 00:14:03,189
okay here we go thank you monica

314
00:14:07,269 --> 00:14:04,630
it's britney

315
00:14:09,189 --> 00:14:07,279
[Music]

316
00:14:10,550 --> 00:14:09,199
what's up y'all i'm monica from sanford

317
00:14:12,550 --> 00:14:10,560
and i'm going to be talking about how

318
00:14:14,150 --> 00:14:12,560
impact events influence the water and

319
00:14:16,470 --> 00:14:14,160
the atmosphere in the late hadean and

320
00:14:17,990 --> 00:14:16,480
early archaean so let's get into it this

321
00:14:19,189 --> 00:14:18,000
is usually the common picture that's

322
00:14:20,629 --> 00:14:19,199
painted when people think about the

323
00:14:22,629 --> 00:14:20,639
hadian right it literally comes from the

324
00:14:24,550 --> 00:14:22,639
word hades and so everybody thinks like

325
00:14:26,470 --> 00:14:24,560
hell you know volcanoes going off the

326
00:14:28,230 --> 00:14:26,480
floor is lava all that good stuff but as

327
00:14:30,389 --> 00:14:28,240
nicole was talking about in your fantasy

328
00:14:32,389 --> 00:14:30,399
talk it likely wasn't like that

329
00:14:33,750 --> 00:14:32,399
we can look at titanium in these zircons

330
00:14:35,670 --> 00:14:33,760
these tiny little minerals that are

331
00:14:37,509 --> 00:14:35,680
about barely the width of a human hair

332
00:14:38,710 --> 00:14:37,519
and these tell us that the melting

333
00:14:40,230 --> 00:14:38,720
temperatures of the rocks during this

334
00:14:42,150 --> 00:14:40,240
time period were a lot lower than we

335
00:14:43,269 --> 00:14:42,160
think and so water was probably the big

336
00:14:44,790 --> 00:14:43,279
culprit here and i'm not just talking

337
00:14:46,230 --> 00:14:44,800
about like little puddles of water there

338
00:14:47,269 --> 00:14:46,240
probably could have been like oceans at

339
00:14:49,269 --> 00:14:47,279
this point

340
00:14:50,949 --> 00:14:49,279
so this time period probably looked a

341
00:14:53,269 --> 00:14:50,959
little bit more something like this um

342
00:14:55,189 --> 00:14:53,279
however despite this image if an alien

343
00:14:56,870 --> 00:14:55,199
observer was also looking for oxygen in

344
00:14:58,470 --> 00:14:56,880
the atmosphere they may have concluded

345
00:15:00,389 --> 00:14:58,480
that the earth was inhabitable um

346
00:15:02,069 --> 00:15:00,399
because there wasn't any oxygen but this

347
00:15:04,470 --> 00:15:02,079
wasn't really the case right life was

348
00:15:06,150 --> 00:15:04,480
already in water so

349
00:15:07,829 --> 00:15:06,160
with that let's talk about what we know

350
00:15:09,509 --> 00:15:07,839
first certain about this time period

351
00:15:11,110 --> 00:15:09,519
first share is that there were zircons

352
00:15:12,710 --> 00:15:11,120
there was already quite a bit of water

353
00:15:13,750 --> 00:15:12,720
there was negligible oxygen in the

354
00:15:15,990 --> 00:15:13,760
atmosphere

355
00:15:18,470 --> 00:15:16,000
that's about it

356
00:15:19,750 --> 00:15:18,480
and this is pretty much a big list of

357
00:15:21,829 --> 00:15:19,760
the things that we don't know this is

358
00:15:23,189 --> 00:15:21,839
not an exhaustive list but there's so so

359
00:15:25,110 --> 00:15:23,199
much we don't know about this time

360
00:15:27,189 --> 00:15:25,120
period yeah the earth has these pesky

361
00:15:29,030 --> 00:15:27,199
pesky weathering processes that uh

362
00:15:31,430 --> 00:15:29,040
pretty much all but get rid of the rock

363
00:15:32,710 --> 00:15:31,440
record during this time period but today

364
00:15:34,310 --> 00:15:32,720
um you know we want to fill in these

365
00:15:36,550 --> 00:15:34,320
missing chapters of the story right the

366
00:15:38,470 --> 00:15:36,560
story of life our story so what i'm

367
00:15:40,230 --> 00:15:38,480
going to be focusing on is the frequency

368
00:15:42,150 --> 00:15:40,240
of smaller impacts during this time

369
00:15:43,749 --> 00:15:42,160
period as well as what was in those

370
00:15:46,949 --> 00:15:43,759
impactors

371
00:15:48,949 --> 00:15:46,959
so this paper uh from martial in 2021

372
00:15:51,110 --> 00:15:48,959
says that the smaller impacts about 10

373
00:15:53,350 --> 00:15:51,120
kilometers in diameter and less were

374
00:15:54,710 --> 00:15:53,360
about 10 times more frequent than free

375
00:15:56,069 --> 00:15:54,720
previously believed in the title says

376
00:15:58,310 --> 00:15:56,079
the later km but this was proposed

377
00:16:00,150 --> 00:15:58,320
throughout the entire archean

378
00:16:01,269 --> 00:16:00,160
the reducing material from these

379
00:16:03,509 --> 00:16:01,279
impactors could have helped to keep

380
00:16:05,829 --> 00:16:03,519
oxygen low during the air key and so

381
00:16:07,509 --> 00:16:05,839
even if oxygen processes were occurring

382
00:16:09,110 --> 00:16:07,519
these impact material this impact

383
00:16:11,269 --> 00:16:09,120
material could have suppressed that

384
00:16:13,269 --> 00:16:11,279
oxygen so we want to investigate this

385
00:16:14,710 --> 00:16:13,279
further so let's look at what was in the

386
00:16:17,670 --> 00:16:14,720
impactors

387
00:16:19,350 --> 00:16:17,680
so this is our enzyme chondrite impactor

388
00:16:20,949 --> 00:16:19,360
these are inner solar system objects

389
00:16:22,470 --> 00:16:20,959
which were formed in the solar nebula

390
00:16:23,990 --> 00:16:22,480
these are high in iron so pretty

391
00:16:25,829 --> 00:16:24,000
reducing but they also brought a little

392
00:16:27,990 --> 00:16:25,839
bit of water and they are very similar

393
00:16:30,470 --> 00:16:28,000
in isotope composition to the crust and

394
00:16:32,710 --> 00:16:30,480
the mantle and so the eh just means high

395
00:16:34,150 --> 00:16:32,720
iron the el means low iron but even if

396
00:16:37,430 --> 00:16:34,160
you look at the low iron case these are

397
00:16:39,030 --> 00:16:37,440
still pretty reduced so uh the model

398
00:16:41,430 --> 00:16:39,040
that we use is called freak c it's an

399
00:16:43,269 --> 00:16:41,440
aqueous geochemistry model uh provided

400
00:16:44,870 --> 00:16:43,279
by the usgs so it is free to use if

401
00:16:46,790 --> 00:16:44,880
you're interested in um and we're going

402
00:16:49,189 --> 00:16:46,800
to use this to calculate the composition

403
00:16:51,590 --> 00:16:49,199
and the ph of the water in equilibrium

404
00:16:53,189 --> 00:16:51,600
with a post impact atmosphere

405
00:16:55,030 --> 00:16:53,199
so first we're going to give the model

406
00:16:56,949 --> 00:16:55,040
some spicy water and next we're going to

407
00:16:59,030 --> 00:16:56,959
put a post impact atmosphere that we

408
00:17:00,949 --> 00:16:59,040
took from zomliadal in 2020 we're going

409
00:17:03,350 --> 00:17:00,959
to use two bars of co2 this paper

410
00:17:04,630 --> 00:17:03,360
considers 2 and 50 bars we've also did a

411
00:17:06,309 --> 00:17:04,640
bunch of runs with other different

412
00:17:09,110 --> 00:17:06,319
levels of co2 but i'm only going to show

413
00:17:11,350 --> 00:17:09,120
you all some of the two bar stuff

414
00:17:12,630 --> 00:17:11,360
so we have three different sizes of

415
00:17:14,150 --> 00:17:12,640
impactors that we looked at and this is

416
00:17:16,630 --> 00:17:14,160
the ph of uh

417
00:17:18,789 --> 00:17:16,640
the post impact atmosphere and the spicy

418
00:17:20,949 --> 00:17:18,799
water that we used these are the masses

419
00:17:22,949 --> 00:17:20,959
of the different impactor sizes that we

420
00:17:24,549 --> 00:17:22,959
used the southpole eiken impactor is

421
00:17:26,630 --> 00:17:24,559
definitely closer in size to these

422
00:17:28,230 --> 00:17:26,640
smaller impactors that we're looking at

423
00:17:29,750 --> 00:17:28,240
for this time period but we also took a

424
00:17:31,590 --> 00:17:29,760
look at some other sizes as well to look

425
00:17:33,029 --> 00:17:31,600
at what the ph was doing and it's a

426
00:17:34,549 --> 00:17:33,039
little price it's a little surprising

427
00:17:37,190 --> 00:17:34,559
right because our water that we

428
00:17:38,630 --> 00:17:37,200
initially put in was a ph of six um

429
00:17:39,750 --> 00:17:38,640
because there's more carbon going on in

430
00:17:41,510 --> 00:17:39,760
this atmosphere so the water would have

431
00:17:43,270 --> 00:17:41,520
been a little bit more acidic but our

432
00:17:44,710 --> 00:17:43,280
results here seem pretty basic

433
00:17:46,630 --> 00:17:44,720
especially for those larger size

434
00:17:48,470 --> 00:17:46,640
impactors and at the cooler temperatures

435
00:17:49,750 --> 00:17:48,480
which is really really interesting

436
00:17:51,430 --> 00:17:49,760
something that we're also doing in

437
00:17:53,190 --> 00:17:51,440
conjunction with this again these

438
00:17:54,950 --> 00:17:53,200
results are like kind of messy at this

439
00:17:56,630 --> 00:17:54,960
point but if anyone wants to talk about

440
00:17:58,310 --> 00:17:56,640
them it's kind of just quite literally

441
00:17:59,750 --> 00:17:58,320
an excel sheet of all these rows of the

442
00:18:01,990 --> 00:17:59,760
different minerals that are

443
00:18:03,909 --> 00:18:02,000
precipitating in the water but we also

444
00:18:05,669 --> 00:18:03,919
used a mineral approximation of an

445
00:18:07,909 --> 00:18:05,679
instantite chondrite impactor in our

446
00:18:10,230 --> 00:18:07,919
freaksy model my advisor was kind enough

447
00:18:11,510 --> 00:18:10,240
to share uh some of the info from her

448
00:18:13,510 --> 00:18:11,520
paper that lists out all the major

449
00:18:15,350 --> 00:18:13,520
species of these impactors and we

450
00:18:18,390 --> 00:18:15,360
equilibrated it with our post-impact

451
00:18:19,750 --> 00:18:18,400
atmosphere as well as our rain water so

452
00:18:20,710 --> 00:18:19,760
we also did that as well again i'm not

453
00:18:21,990 --> 00:18:20,720
really going to be showing you here but

454
00:18:23,430 --> 00:18:22,000
if anyone wants to discuss that i'm

455
00:18:24,789 --> 00:18:23,440
absolutely happy to

456
00:18:26,710 --> 00:18:24,799
so then we're also going to take all

457
00:18:28,390 --> 00:18:26,720
these things equilibrated over various

458
00:18:30,390 --> 00:18:28,400
volumes of water various temperatures

459
00:18:32,710 --> 00:18:30,400
various co2 concentrations all that good

460
00:18:34,549 --> 00:18:32,720
stuff and some emerging results that we

461
00:18:36,549 --> 00:18:34,559
have which are going to come very soon

462
00:18:38,549 --> 00:18:36,559
is that these highly reduced smaller

463
00:18:39,990 --> 00:18:38,559
impacts which again are maybe possibly

464
00:18:41,990 --> 00:18:40,000
you know 10 times more frequent than we

465
00:18:44,230 --> 00:18:42,000
thought could have possibly worked to

466
00:18:46,870 --> 00:18:44,240
suppress these oxidation efforts and

467
00:18:48,390 --> 00:18:46,880
subsequently oxygen as a biosignature so

468
00:18:50,630 --> 00:18:48,400
it could be that these impacts could act

469
00:18:52,310 --> 00:18:50,640
as a potential sink of oxygen during

470
00:18:55,510 --> 00:18:52,320
this time period but for now we're just

471
00:18:57,110 --> 00:18:55,520
going to look at what the water ph means

472
00:18:59,029 --> 00:18:57,120
so it results the water is not as spicy

473
00:19:01,029 --> 00:18:59,039
as we thought these larger impacts are

474
00:19:03,350 --> 00:19:01,039
probably destroying more co2 which is

475
00:19:05,029 --> 00:19:03,360
going to leave behind a higher ph um but

476
00:19:07,270 --> 00:19:05,039
why is ph really important in this case

477
00:19:08,630 --> 00:19:07,280
so a lot of weathering reactions are ph

478
00:19:10,549 --> 00:19:08,640
dependent it's these it's because of

479
00:19:12,070 --> 00:19:10,559
these weathering reactions that we don't

480
00:19:14,549 --> 00:19:12,080
have a lot of you know concrete physical

481
00:19:16,470 --> 00:19:14,559
evidence of this time period so reaction

482
00:19:18,150 --> 00:19:16,480
rates for take for example pyrite tend

483
00:19:19,990 --> 00:19:18,160
to be a little bit slower under basic

484
00:19:22,470 --> 00:19:20,000
condition and so these weathering and

485
00:19:24,390 --> 00:19:22,480
oxidation reactions might be slower

486
00:19:25,990 --> 00:19:24,400
after larger impacts so then what's that

487
00:19:28,390 --> 00:19:26,000
going to mean for oxygen growth in the

488
00:19:29,990 --> 00:19:28,400
context of more frequent smaller impacts

489
00:19:31,990 --> 00:19:30,000
but of course like i was saying there's

490
00:19:33,750 --> 00:19:32,000
more stuff to test right levels of co2

491
00:19:35,510 --> 00:19:33,760
different temperatures we are also going

492
00:19:36,789 --> 00:19:35,520
to be looking at the angle of impacts as

493
00:19:38,470 --> 00:19:36,799
well as kind of the spray from the

494
00:19:40,310 --> 00:19:38,480
ejecta that could have made it harder

495
00:19:41,430 --> 00:19:40,320
for photosynthetic organisms to you know

496
00:19:43,830 --> 00:19:41,440
do their job

497
00:19:45,830 --> 00:19:43,840
but here are my main takeaways for y'all

498
00:19:47,190 --> 00:19:45,840
the late hadean earlier kian impacts

499
00:19:48,710 --> 00:19:47,200
were tiny but mighty and they could have

500
00:19:50,470 --> 00:19:48,720
brought a lot of reducing power to the

501
00:19:52,070 --> 00:19:50,480
ancient hydrosphere and so we want to

502
00:19:54,549 --> 00:19:52,080
ask the questions are these impactors

503
00:19:56,549 --> 00:19:54,559
biosignature suppressants and then how

504
00:19:58,310 --> 00:19:56,559
do these impactors influence weathering

505
00:19:59,590 --> 00:19:58,320
reactions

506
00:20:01,270 --> 00:19:59,600
the hydrosphere is going to be the key

507
00:20:02,950 --> 00:20:01,280
to filling in these missing chapters of

508
00:20:05,270 --> 00:20:02,960
our story right we're astrobiologists we

509
00:20:06,549 --> 00:20:05,280
always follow the water and specifically

510
00:20:08,950 --> 00:20:06,559
the hydrosphere will be the key to

511
00:20:10,470 --> 00:20:08,960
thinking about how oxygen arose so later

512
00:20:12,630 --> 00:20:10,480
on in the very later key and at the

513
00:20:14,070 --> 00:20:12,640
start of the great oxidation event we

514
00:20:15,830 --> 00:20:14,080
could really benefit from a time machine

515
00:20:17,270 --> 00:20:15,840
if anyone's working on that it's really

516
00:20:18,310 --> 00:20:17,280
really hard again it's really hard to

517
00:20:19,990 --> 00:20:18,320
overstate

518
00:20:21,029 --> 00:20:20,000
how much little physical evidence we had

519
00:20:22,789 --> 00:20:21,039
but for right now we're going to work

520
00:20:24,390 --> 00:20:22,799
with that and if you're a fieldwork

521
00:20:26,470 --> 00:20:24,400
person please give me more hadees or

522
00:20:30,149 --> 00:20:26,480
cons i'd really appreciate it and with

523
00:20:33,350 --> 00:20:31,590
with that thank you all so much if i

524
00:20:34,470 --> 00:20:33,360
have time for questions i would love to

525
00:20:38,950 --> 00:20:34,480
take them and thank you all to the

526
00:20:42,230 --> 00:20:40,789
do you have time um for a question so

527
00:20:43,590 --> 00:20:42,240
please come on up to the mic if you have

528
00:20:45,350 --> 00:20:43,600
a question i would also just like to

529
00:20:48,870 --> 00:20:45,360
make a formal request that we include

530
00:20:51,190 --> 00:20:48,880
more brittany in our presentations so

531
00:20:53,270 --> 00:20:51,200
next time i have high expectations of

532
00:20:55,270 --> 00:20:53,280
everyone so yes we have a question here

533
00:20:57,430 --> 00:20:55,280
hi my name's matt i'm also from stanford

534
00:20:59,750 --> 00:20:57,440
i think you know me i think so

535
00:21:01,750 --> 00:20:59,760
uh so actually so uh you mentioned uh

536
00:21:03,350 --> 00:21:01,760
they're sort of the late sort of roughly

537
00:21:05,590 --> 00:21:03,360
around the great oxidation event i was

538
00:21:07,590 --> 00:21:05,600
wondering what the impact rates at that

539
00:21:09,990 --> 00:21:07,600
time are estimated to be and whether or

540
00:21:11,270 --> 00:21:10,000
not this could be a source of oxygen

541
00:21:13,430 --> 00:21:11,280
suppressants

542
00:21:15,430 --> 00:21:13,440
before the great oxidation event yeah

543
00:21:17,590 --> 00:21:15,440
yeah great question um so it's not

544
00:21:18,789 --> 00:21:17,600
really known what the impactor rates

545
00:21:20,950 --> 00:21:18,799
were during this time period it's

546
00:21:22,549 --> 00:21:20,960
definitely believed that as the archaean

547
00:21:24,149 --> 00:21:22,559
and specifically the archaean went on

548
00:21:25,590 --> 00:21:24,159
through time that the impact rates

549
00:21:27,510 --> 00:21:25,600
decreased and decreased we don't really

550
00:21:29,669 --> 00:21:27,520
know by like the factor or like you know

551
00:21:31,190 --> 00:21:29,679
what was happening there um but overall

552
00:21:32,789 --> 00:21:31,200
the impactors were definitely less

553
00:21:34,710 --> 00:21:32,799
frequent as you get later on into the

554
00:21:35,990 --> 00:21:34,720
archaean um but again the issue is you

555
00:21:37,510 --> 00:21:36,000
know how frequent and what were the

556
00:21:39,430 --> 00:21:37,520
sizes of these impactors you know all

557
00:21:41,510 --> 00:21:39,440
that good stuff so yeah it's still still

558
00:21:43,830 --> 00:21:41,520
not really well known

559
00:21:45,110 --> 00:21:43,840
thank you awesome thank you so much yeah

560
00:21:47,270 --> 00:21:45,120
i was wondering how do you think when

561
00:21:48,870 --> 00:21:47,280
they're so small and so you know how do

562
00:21:50,230 --> 00:21:48,880
you figure out um what was going on

563
00:21:52,630 --> 00:21:50,240
there i think that's a really tough

564
00:21:54,130 --> 00:21:52,640
problem um so let's thank uh monica

565
00:21:57,270 --> 00:21:54,140
again

566
00:21:58,950 --> 00:21:57,280
[Applause]

567
00:22:02,630 --> 00:21:58,960
and next up we're staying in the

568
00:22:05,029 --> 00:22:02,640
archaean and we have uh nathan yee uh

569
00:22:08,549 --> 00:22:05,039
from rutgers coming to talk to us

570
00:22:11,430 --> 00:22:08,559
about uh anoxic photochemical

571
00:22:14,549 --> 00:22:11,440
uh reactions and pyrite in the archaean

572
00:22:17,029 --> 00:22:14,559
thank you nathan thank you shauna

573
00:22:20,870 --> 00:22:19,029
okay so i'm going to present a paper

574
00:22:23,110 --> 00:22:20,880
entitled anoxic photochemical weathering

575
00:22:25,750 --> 00:22:23,120
of pyrite our key incontinence

576
00:22:28,149 --> 00:22:25,760
uh postdoc chihuahua and phd student

577
00:22:30,950 --> 00:22:28,159
winnie liu were co-first authors of this

578
00:22:36,630 --> 00:22:34,070
so our research is motivated by our

579
00:22:38,549 --> 00:22:36,640
interest in the biology of sulfur sulfur

580
00:22:39,669 --> 00:22:38,559
is an essential element of all living

581
00:22:42,630 --> 00:22:39,679
things

582
00:22:45,029 --> 00:22:42,640
it's found in the amino acids cysteine

583
00:22:47,510 --> 00:22:45,039
and in methionine

584
00:22:48,710 --> 00:22:47,520
and in these amino acids sulfur plays

585
00:22:51,029 --> 00:22:48,720
numerous

586
00:22:52,630 --> 00:22:51,039
critical biological functions

587
00:22:55,350 --> 00:22:52,640
including the maintenance of redox

588
00:22:57,669 --> 00:22:55,360
homeostasis the formation of disulfide

589
00:22:59,830 --> 00:22:57,679
bonds and protein structure in

590
00:23:02,149 --> 00:22:59,840
cross-linking the binding of metal

591
00:23:05,830 --> 00:23:02,159
cofactors and electron transfer

592
00:23:10,470 --> 00:23:07,750
so cysteine and methionine are

593
00:23:13,590 --> 00:23:10,480
synthesized inside the cell via a

594
00:23:16,950 --> 00:23:13,600
simulatory sulfate reduction

595
00:23:19,590 --> 00:23:16,960
so all living things have not all all

596
00:23:22,789 --> 00:23:19,600
three domains of life have evolved

597
00:23:25,430 --> 00:23:22,799
biological pathways to assimilate

598
00:23:27,990 --> 00:23:25,440
dissolves sulfate in the environment and

599
00:23:30,789 --> 00:23:28,000
incorporate it into the cell for the

600
00:23:34,310 --> 00:23:30,799
synthesis of these two amino acids

601
00:23:37,669 --> 00:23:34,320
so since sulfate is imported into the

602
00:23:40,390 --> 00:23:37,679
cell via very specific membrane bound

603
00:23:42,549 --> 00:23:40,400
transporters and is activated to

604
00:23:44,149 --> 00:23:42,559
adenosine phosphosulfate which is then

605
00:23:45,750 --> 00:23:44,159
converted to phospho-adenosine

606
00:23:48,149 --> 00:23:45,760
phosphosulfate

607
00:23:50,630 --> 00:23:48,159
then reduced via sulfite to hydrogen

608
00:23:53,350 --> 00:23:50,640
sulfide which is then incorporated into

609
00:23:57,110 --> 00:23:53,360
amino acids via the action of cysteine

610
00:24:01,029 --> 00:23:58,630
so our

611
00:24:02,830 --> 00:24:01,039
interest is understanding the sources of

612
00:24:06,789 --> 00:24:02,840
sulfate on the early

613
00:24:08,630 --> 00:24:06,799
earth so pyrite is the most abundant

614
00:24:10,390 --> 00:24:08,640
sulfide mineral in the earth's crust and

615
00:24:11,590 --> 00:24:10,400
the principle source of sulfur to the

616
00:24:14,070 --> 00:24:11,600
geosphere

617
00:24:16,950 --> 00:24:14,080
and our hypothesis is that the chemical

618
00:24:19,350 --> 00:24:16,960
breakdown of pyrite and the production

619
00:24:22,470 --> 00:24:19,360
of sulfate on the early earth was

620
00:24:24,630 --> 00:24:22,480
mediated by photochemical reactions with

621
00:24:26,390 --> 00:24:24,640
dissolved ferrous iron in ferruginous

622
00:24:28,549 --> 00:24:26,400
waters

623
00:24:30,549 --> 00:24:28,559
because the earth had an ozone-free

624
00:24:31,750 --> 00:24:30,559
stratosphere at this time ultraviolet

625
00:24:34,470 --> 00:24:31,760
light could penetrate through the

626
00:24:37,269 --> 00:24:34,480
atmosphere and interact with dissolved

627
00:24:40,470 --> 00:24:37,279
ferrous iron in surface waters

628
00:24:43,190 --> 00:24:40,480
this is a high quantum yield reaction

629
00:24:44,630 --> 00:24:43,200
where ferrous iron is photo-oxidized to

630
00:24:49,590 --> 00:24:44,640
ferric iron

631
00:24:51,269 --> 00:24:49,600
react with pyritic sulfur

632
00:24:55,190 --> 00:24:51,279
to oxidize

633
00:24:57,350 --> 00:24:55,200
sulfide minerals to form sulfate

634
00:24:59,590 --> 00:24:57,360
sulfate production river sediments could

635
00:25:02,789 --> 00:24:59,600
then be transported to the oceans where

636
00:25:04,789 --> 00:25:02,799
sulfate was assimilated by the biosphere

637
00:25:06,710 --> 00:25:04,799
this chemical reaction also produces

638
00:25:08,470 --> 00:25:06,720
lots of acid

639
00:25:10,390 --> 00:25:08,480
and releases ferrous iron from the

640
00:25:12,710 --> 00:25:10,400
pyrite structure which could then be

641
00:25:15,430 --> 00:25:12,720
re-oxidized to continuously

642
00:25:17,269 --> 00:25:15,440
continually sustain this reaction

643
00:25:18,630 --> 00:25:17,279
so to test this photochemical weathering

644
00:25:21,990 --> 00:25:18,640
hypothesis we constructed an

645
00:25:23,110 --> 00:25:22,000
experimental setup where we placed a uv

646
00:25:26,070 --> 00:25:23,120
lamp

647
00:25:29,669 --> 00:25:26,080
in the center surrounded by six uv

648
00:25:32,230 --> 00:25:29,679
transparent quartz reaction vessels

649
00:25:34,149 --> 00:25:32,240
we suspended crushed pyrite grains in

650
00:25:35,510 --> 00:25:34,159
deoxygenated solutions of ferrous

651
00:25:37,990 --> 00:25:35,520
chloride

652
00:25:39,750 --> 00:25:38,000
we capped and crimped these reaction

653
00:25:41,430 --> 00:25:39,760
vessels purged with nitrogen and

654
00:25:43,350 --> 00:25:41,440
conducted all these experiments under

655
00:25:44,870 --> 00:25:43,360
strict anoxic conditions

656
00:25:46,789 --> 00:25:44,880
we turned on the light and then we

657
00:25:49,269 --> 00:25:46,799
sampled the headspace for a change to

658
00:25:51,190 --> 00:25:49,279
observe changes in the gas phase

659
00:25:53,190 --> 00:25:51,200
sample the aqueous phase as well as the

660
00:25:55,590 --> 00:25:53,200
salts phases to track the mineral

661
00:25:57,510 --> 00:25:55,600
transformation reactions

662
00:25:59,750 --> 00:25:57,520
and this is what we observed

663
00:26:00,870 --> 00:25:59,760
in our dark control experiments we

664
00:26:03,830 --> 00:26:00,880
observed

665
00:26:07,750 --> 00:26:03,840
no change in sulfate over time

666
00:26:10,390 --> 00:26:07,760
and no change in ph over time

667
00:26:13,110 --> 00:26:10,400
but when we turned on the lamp we saw an

668
00:26:15,909 --> 00:26:13,120
enormous amount of sulfate being formed

669
00:26:18,070 --> 00:26:15,919
up to two millimolars of sulfate in

670
00:26:20,549 --> 00:26:18,080
aqueous solution after a couple weeks

671
00:26:22,789 --> 00:26:20,559
and this was concurrent to acidification

672
00:26:24,549 --> 00:26:22,799
of the waters

673
00:26:26,070 --> 00:26:24,559
to test the geological significance of

674
00:26:27,190 --> 00:26:26,080
this reaction we repeated the

675
00:26:29,390 --> 00:26:27,200
experiments

676
00:26:31,510 --> 00:26:29,400
with this archaean rock sample this is a

677
00:26:34,310 --> 00:26:31,520
2.65 year old

678
00:26:36,549 --> 00:26:34,320
pyritic shale collected from the arroyo

679
00:26:38,549 --> 00:26:36,559
formation in western australia

680
00:26:41,110 --> 00:26:38,559
we crushed the top two thirds of this

681
00:26:42,070 --> 00:26:41,120
sample which contained pyrite nodules at

682
00:26:43,990 --> 00:26:42,080
the top

683
00:26:45,430 --> 00:26:44,000
and finally disseminated

684
00:26:48,789 --> 00:26:45,440
pyrite grains

685
00:26:52,070 --> 00:26:50,549
and we observed the same thing in the

686
00:26:54,710 --> 00:26:52,080
dark controls there was no sulfate

687
00:26:56,870 --> 00:26:54,720
production no change in ph

688
00:26:58,070 --> 00:26:56,880
when we irradiated this pyrite

689
00:26:59,350 --> 00:26:58,080
suspension

690
00:27:02,390 --> 00:26:59,360
we produced

691
00:27:05,430 --> 00:27:02,400
sulfate concurrent to a decrease in

692
00:27:09,909 --> 00:27:07,909
we also tracked the mobilization and

693
00:27:11,590 --> 00:27:09,919
release of transition metals and shown

694
00:27:13,190 --> 00:27:11,600
here is the copper data

695
00:27:15,269 --> 00:27:13,200
so in the dark controls there was no

696
00:27:17,269 --> 00:27:15,279
release of copper from

697
00:27:19,350 --> 00:27:17,279
either the pyrite experiment or the

698
00:27:22,070 --> 00:27:19,360
archaean shale experiment but in both

699
00:27:24,470 --> 00:27:22,080
these experiments when we irradiated

700
00:27:25,750 --> 00:27:24,480
the samples with ultraviolet light

701
00:27:27,430 --> 00:27:25,760
we saw

702
00:27:29,990 --> 00:27:27,440
large amounts of copper being released

703
00:27:31,590 --> 00:27:30,000
into this in the aqueous phase

704
00:27:33,350 --> 00:27:31,600
and we think this might have been an

705
00:27:34,789 --> 00:27:33,360
important reaction for

706
00:27:39,110 --> 00:27:34,799
the release of transition metals

707
00:27:42,870 --> 00:27:40,630
so uh

708
00:27:44,789 --> 00:27:42,880
my former postdoc geo ohio is now a

709
00:27:45,990 --> 00:27:44,799
faculty member

710
00:27:47,350 --> 00:27:46,000
in the university of science and

711
00:27:49,990 --> 00:27:47,360
technology

712
00:27:52,870 --> 00:27:50,000
of china constructed a photo geochemical

713
00:27:54,470 --> 00:27:52,880
model to test how much sulfate could

714
00:27:56,310 --> 00:27:54,480
have been formed

715
00:27:57,590 --> 00:27:56,320
by this photochemical weathering

716
00:27:59,430 --> 00:27:57,600
mechanism

717
00:28:02,710 --> 00:27:59,440
so what he found was that sulfate

718
00:28:05,669 --> 00:28:02,720
production increased over time

719
00:28:08,070 --> 00:28:05,679
as the continents formed throughout the

720
00:28:11,269 --> 00:28:08,080
archaean eon

721
00:28:12,789 --> 00:28:11,279
this is the the dashboard line shows the

722
00:28:15,830 --> 00:28:12,799
estimated amount

723
00:28:16,950 --> 00:28:15,840
of sulfate production during riverine

724
00:28:19,029 --> 00:28:16,960
weathering

725
00:28:20,549 --> 00:28:19,039
this envelope represents the uncertainty

726
00:28:22,149 --> 00:28:20,559
in this calculation and there was large

727
00:28:23,590 --> 00:28:22,159
uncertainties associated with the

728
00:28:25,510 --> 00:28:23,600
physical

729
00:28:28,389 --> 00:28:25,520
crustal erosion rates and pyrite

730
00:28:30,149 --> 00:28:28,399
transport times but we think that this

731
00:28:33,590 --> 00:28:30,159
photochemical weathering mechanism could

732
00:28:36,470 --> 00:28:33,600
have produced as much uh sulfate as

733
00:28:38,630 --> 00:28:36,480
volcanic outgassing

734
00:28:39,750 --> 00:28:38,640
okay so to quickly summarize three

735
00:28:41,990 --> 00:28:39,760
things

736
00:28:44,710 --> 00:28:42,000
uh one is ultraviolet can chemically

737
00:28:47,590 --> 00:28:44,720
break down pyrite two this reaction

738
00:28:48,950 --> 00:28:47,600
doesn't require any atmospheric oxygen

739
00:28:51,909 --> 00:28:48,960
and three

740
00:28:53,430 --> 00:28:51,919
the amount of land exposed to sunlight

741
00:28:55,350 --> 00:28:53,440
could have been a major factor

742
00:28:58,549 --> 00:28:55,360
contributing the amount of sulfate

743
00:29:00,870 --> 00:28:58,559
delivered to the early oceans that i

744
00:29:03,029 --> 00:29:00,880
thank the nasa astro

745
00:29:05,350 --> 00:29:03,039
nasa astrobiology institute and the nasa

746
00:29:07,430 --> 00:29:05,360
exobiology program funding as well as

747
00:29:17,430 --> 00:29:07,440
the national science foundation thank

748
00:29:21,190 --> 00:29:18,789
uh we have some time for questions so go

749
00:29:23,430 --> 00:29:21,200
ahead sean thompson goldman nasa goddard

750
00:29:25,269 --> 00:29:23,440
space flight center um does this process

751
00:29:27,590 --> 00:29:25,279
also work regardless of the source of

752
00:29:29,830 --> 00:29:27,600
the iron oxides in other words if it was

753
00:29:32,470 --> 00:29:29,840
iron oxidizing bacteria producing them

754
00:29:34,230 --> 00:29:32,480
would this would this process still work

755
00:29:36,789 --> 00:29:34,240
more or less the same way

756
00:29:38,389 --> 00:29:36,799
right so i think your question is could

757
00:29:41,029 --> 00:29:38,399
microorganisms

758
00:29:42,789 --> 00:29:41,039
oxidize ferrous iron to ferric iron and

759
00:29:44,870 --> 00:29:42,799
with this ferric iron still chemically

760
00:29:47,430 --> 00:29:44,880
react uh with

761
00:29:48,710 --> 00:29:47,440
the pyrite and that's definitely yes

762
00:29:50,389 --> 00:29:48,720
so um

763
00:29:52,149 --> 00:29:50,399
one thing i should mention is that these

764
00:29:55,590 --> 00:29:52,159
reactions as mentioned in the earlier

765
00:30:00,310 --> 00:29:55,600
talk is strongly dependent on ph

766
00:30:02,870 --> 00:30:01,510
sulfur cycle

767
00:30:04,870 --> 00:30:02,880
that under

768
00:30:05,990 --> 00:30:04,880
acidic conditions

769
00:30:08,470 --> 00:30:06,000
there are

770
00:30:10,870 --> 00:30:08,480
iron oxidizing bacteria that oxidize

771
00:30:13,510 --> 00:30:10,880
ferrous iron to ferric iron that drive

772
00:30:16,230 --> 00:30:13,520
this chemical process but those uh

773
00:30:19,269 --> 00:30:16,240
chemolithotrophs are arrows so they

774
00:30:24,310 --> 00:30:19,279
actually need oxygen for the respiration

775
00:30:26,549 --> 00:30:24,320
to catalyze that reaction okay thank you

776
00:30:31,029 --> 00:30:26,559
awesome so you know i want to ask about

777
00:30:32,870 --> 00:30:31,039
mars of course so what do you think um

778
00:30:35,029 --> 00:30:32,880
what do you think is going on in terms

779
00:30:36,389 --> 00:30:35,039
of is this possibly how we're getting so

780
00:30:37,909 --> 00:30:36,399
much of the iron three plus on the

781
00:30:38,950 --> 00:30:37,919
surface you think this is playing a role

782
00:30:40,630 --> 00:30:38,960
there

783
00:30:42,870 --> 00:30:40,640
um and you know we're seeing a lot of

784
00:30:44,710 --> 00:30:42,880
sulfate you know what do you do you have

785
00:30:46,389 --> 00:30:44,720
anything to say about well the large

786
00:30:48,710 --> 00:30:46,399
amount of sulfate minerals on mars is

787
00:30:49,669 --> 00:30:48,720
very intriguing and i definitely think

788
00:30:51,750 --> 00:30:49,679
that

789
00:30:53,990 --> 00:30:51,760
photochemical reactions played a role in

790
00:30:56,710 --> 00:30:54,000
sulfate formation either through the

791
00:30:57,909 --> 00:30:56,720
direct action of ultraviolet light with

792
00:31:00,710 --> 00:30:57,919
volcanic

793
00:31:03,509 --> 00:31:00,720
sulfur dioxide to disproportionate that

794
00:31:05,269 --> 00:31:03,519
that sulfur dioxide to form the sulfate

795
00:31:07,909 --> 00:31:05,279
but also potentially through an indirect

796
00:31:10,230 --> 00:31:07,919
mechanism where if light

797
00:31:12,710 --> 00:31:10,240
photo oxidizes uh pharisein to ferric

798
00:31:14,710 --> 00:31:12,720
iron then that ferrakin will chemically

799
00:31:16,870 --> 00:31:14,720
react with either elemental sulfur or

800
00:31:18,710 --> 00:31:16,880
sulfide to produce

801
00:31:19,750 --> 00:31:18,720
sulfate

802
00:31:21,830 --> 00:31:19,760
thank you and i think you have another

803
00:31:23,190 --> 00:31:21,840
question bob yeah thanks nathan that's

804
00:31:25,029 --> 00:31:23,200
really interesting earlier this

805
00:31:26,310 --> 00:31:25,039
afternoon ariel and barr gave a

806
00:31:30,789 --> 00:31:26,320
beautiful talk

807
00:31:33,350 --> 00:31:30,799
on revisiting the whiff of oxygen idea

808
00:31:34,710 --> 00:31:33,360
it seems like there's a lot of evidence

809
00:31:37,990 --> 00:31:34,720
that there were

810
00:31:39,990 --> 00:31:38,000
some something analogous to oxygen um

811
00:31:42,230 --> 00:31:40,000
certainly some kind of

812
00:31:43,909 --> 00:31:42,240
electron acceptor and i wonder whether

813
00:31:45,830 --> 00:31:43,919
sulfate

814
00:31:47,990 --> 00:31:45,840
that you described might actually be

815
00:31:48,710 --> 00:31:48,000
this this whiff that they're seeing if

816
00:31:50,149 --> 00:31:48,720
it's

817
00:31:52,710 --> 00:31:50,159
um you know you're talking about

818
00:31:54,149 --> 00:31:52,720
extremely low levels of o2 there would

819
00:31:56,470 --> 00:31:54,159
have been a lot of sulfate around and

820
00:31:57,750 --> 00:31:56,480
that seems like a much more logical

821
00:32:00,950 --> 00:31:57,760
um

822
00:32:04,310 --> 00:32:00,960
electron except

823
00:32:05,430 --> 00:32:04,320
right so um this paper uh has gone

824
00:32:08,070 --> 00:32:05,440
through a peer review as science

825
00:32:09,509 --> 00:32:08,080
advances and we got similar questions

826
00:32:10,870 --> 00:32:09,519
and i'm happy to report that the

827
00:32:13,110 --> 00:32:10,880
manuscript was finally accepted for

828
00:32:14,630 --> 00:32:13,120
publication last week

829
00:32:18,470 --> 00:32:14,640
what i want to say is that this does not

830
00:32:22,870 --> 00:32:20,710
pirate weathering it's a complementary

831
00:32:24,789 --> 00:32:22,880
mechanism and i think

832
00:32:26,950 --> 00:32:24,799
both could have been at play in the late

833
00:32:29,190 --> 00:32:26,960
archean

834
00:32:30,630 --> 00:32:29,200
though i do think this reaction may have

835
00:32:33,029 --> 00:32:30,640
played a bigger role

836
00:32:34,630 --> 00:32:33,039
prior to the evolution of oxygenic

837
00:32:37,190 --> 00:32:34,640
photosynthesis

838
00:32:39,990 --> 00:32:37,200
uh what we did do with ariel ombar's

839
00:32:41,669 --> 00:32:40,000
the recent science advances paper was uh

840
00:32:43,509 --> 00:32:41,679
we took the

841
00:32:44,789 --> 00:32:43,519
estimates of this low

842
00:32:47,430 --> 00:32:44,799
o2

843
00:32:50,070 --> 00:32:47,440
constraint that they discovered

844
00:32:52,630 --> 00:32:50,080
and tried to calculate how much sulfate

845
00:32:54,230 --> 00:32:52,640
could have been produced using this low

846
00:32:56,870 --> 00:32:54,240
o2 condition

847
00:32:58,950 --> 00:32:56,880
and we think that um in order to

848
00:33:00,870 --> 00:32:58,960
reconcile with the geological evidence

849
00:33:03,509 --> 00:33:00,880
this there must have been additional

850
00:33:06,310 --> 00:33:03,519
oxidants to weather pyrite in addition

851
00:33:08,870 --> 00:33:06,320
to to oxygen at that uh during the

852
00:33:11,269 --> 00:33:08,880
bikini on and we think ferric iron

853
00:33:14,950 --> 00:33:11,279
from these photochemical sources is a

854
00:33:18,870 --> 00:33:16,789
fantastic thank you so now we're in our

855
00:33:22,149 --> 00:33:18,880
slot um that has

856
00:33:24,149 --> 00:33:22,159
uh our withdrawn talk so we have um you

857
00:33:25,269 --> 00:33:24,159
know about eight minutes to ask any

858
00:33:26,710 --> 00:33:25,279
questions you have so if you guys just

859
00:33:28,310 --> 00:33:26,720
want to line up at the microphones we

860
00:33:30,230 --> 00:33:28,320
can do that and we'll start with um i

861
00:33:31,590 --> 00:33:30,240
have a couple of questions online and

862
00:33:33,590 --> 00:33:31,600
anyone who's listening online feel free

863
00:33:35,269 --> 00:33:33,600
to keep dropping those questions in um

864
00:33:37,190 --> 00:33:35,279
so we actually have two questions for

865
00:33:38,789 --> 00:33:37,200
nicole so maybe if you just want to come

866
00:33:40,470 --> 00:33:38,799
up to the podium that then the online

867
00:33:43,269 --> 00:33:40,480
participants can hear you

868
00:33:46,389 --> 00:33:43,279
um so the first question was um from

869
00:33:47,590 --> 00:33:46,399
maggie thompson and they asked what are

870
00:33:49,110 --> 00:33:47,600
your thoughts on the ways in which we

871
00:33:51,669 --> 00:33:49,120
can try to determine if earth's early

872
00:33:53,669 --> 00:33:51,679
atmosphere was reducing or oxidizing for

873
00:33:58,070 --> 00:33:53,679
example are there particular experiments

874
00:34:03,590 --> 00:34:01,190
so i think um some of the the modeling

875
00:34:05,269 --> 00:34:03,600
that monica described i think is is a

876
00:34:07,830 --> 00:34:05,279
good way to start that we do know that

877
00:34:09,829 --> 00:34:07,840
there have been multiple impacts from

878
00:34:12,310 --> 00:34:09,839
ents to tichondrites comets other kinds

879
00:34:14,149 --> 00:34:12,320
of asteroids and really understanding

880
00:34:17,430 --> 00:34:14,159
how that

881
00:34:19,589 --> 00:34:17,440
reaction of the impact entry temperature

882
00:34:21,430 --> 00:34:19,599
velocity the breakup of the materials

883
00:34:23,990 --> 00:34:21,440
how that could affect

884
00:34:25,589 --> 00:34:24,000
any any kind of atmosphere that that

885
00:34:29,510 --> 00:34:25,599
that existed

886
00:34:32,310 --> 00:34:29,520
under various uh compositional

887
00:34:34,869 --> 00:34:32,320
uh ranges i guess uh from fully reducing

888
00:34:37,349 --> 00:34:34,879
to fully oxidizing the terrestrial

889
00:34:39,270 --> 00:34:37,359
samples zircons

890
00:34:42,230 --> 00:34:39,280
other other materials that have been

891
00:34:44,710 --> 00:34:42,240
investigated suggest that earth's mantle

892
00:34:46,710 --> 00:34:44,720
was oxidizing and and if that material

893
00:34:48,629 --> 00:34:46,720
is coming up from

894
00:34:50,470 --> 00:34:48,639
from the surface and then be being

895
00:34:52,629 --> 00:34:50,480
incorporated into our atmosphere that's

896
00:34:54,069 --> 00:34:52,639
that's one um component that that should

897
00:34:56,230 --> 00:34:54,079
be investigated a little bit more

898
00:34:57,349 --> 00:34:56,240
closely i think too

899
00:34:59,109 --> 00:34:57,359
awesome and then we have another

900
00:35:02,550 --> 00:34:59,119
question for you um and this is from

901
00:35:04,230 --> 00:35:02,560
ricardo cabrera and he asks given that

902
00:35:05,829 --> 00:35:04,240
the moon received a huge amount of

903
00:35:08,470 --> 00:35:05,839
impactors it should have been supplied

904
00:35:09,670 --> 00:35:08,480
with organics too is there any evidence

905
00:35:12,230 --> 00:35:09,680
on that

906
00:35:14,069 --> 00:35:12,240
is jamie in the room

907
00:35:15,589 --> 00:35:14,079
so that that's a really really

908
00:35:17,589 --> 00:35:15,599
interesting question and it turns out

909
00:35:19,349 --> 00:35:17,599
that the abundance of organics that have

910
00:35:22,069 --> 00:35:19,359
been investigated in the lunar soil

911
00:35:24,069 --> 00:35:22,079
samples from apollo is negligible

912
00:35:26,230 --> 00:35:24,079
and that's because the moon doesn't have

913
00:35:27,270 --> 00:35:26,240
an atmosphere to protect the surface

914
00:35:28,230 --> 00:35:27,280
from

915
00:35:31,990 --> 00:35:28,240
any

916
00:35:35,109 --> 00:35:32,000
radiation cosmic rays solar wind all of

917
00:35:37,589 --> 00:35:35,119
that so organic materials are not well

918
00:35:39,430 --> 00:35:37,599
preserved if at all in

919
00:35:41,349 --> 00:35:39,440
in the the soil in the regolith that

920
00:35:42,870 --> 00:35:41,359
we've measured so far

921
00:35:44,790 --> 00:35:42,880
awesome thank you so much and those are

922
00:35:46,470 --> 00:35:44,800
our online questions so if anyone else

923
00:35:47,910 --> 00:35:46,480
has a question that they would like to

924
00:35:49,990 --> 00:35:47,920
ask any three of our speakers or a

925
00:35:52,150 --> 00:35:50,000
preemptive question for someone coming

926
00:35:55,589 --> 00:35:52,160
up that's fine go ahead uh actually

927
00:35:57,109 --> 00:35:55,599
based on the last question um so a lot

928
00:35:58,950 --> 00:35:57,119
of worlds in the outer solar system are

929
00:36:01,670 --> 00:35:58,960
kind of reddish because of these stolens

930
00:36:03,510 --> 00:36:01,680
which are organic compounds yet

931
00:36:04,550 --> 00:36:03,520
those are often on worlds that have no

932
00:36:05,670 --> 00:36:04,560
atmosphere

933
00:36:07,750 --> 00:36:05,680
so

934
00:36:13,030 --> 00:36:07,760
how do they survive and those organics

935
00:36:16,630 --> 00:36:15,589
i don't know the answer to that question

936
00:36:20,630 --> 00:36:16,640
um

937
00:36:22,470 --> 00:36:20,640
i don't know uh

938
00:36:25,589 --> 00:36:22,480
i i don't know that anyone's looked for

939
00:36:29,109 --> 00:36:25,599
tholens in the lunar regolith um for one

940
00:36:33,910 --> 00:36:31,270
and i don't know the chemical reaction

941
00:36:35,990 --> 00:36:33,920
to create a tholen for another so i'm i

942
00:36:39,030 --> 00:36:36,000
don't have an answer to that

943
00:36:40,390 --> 00:36:39,040
so uh steely andrew steele has commented

944
00:36:43,349 --> 00:36:40,400
online and said that there is graphite

945
00:36:45,109 --> 00:36:43,359
and graphite whiskers in lunar samples

946
00:36:47,750 --> 00:36:45,119
just fyi right

947
00:36:49,589 --> 00:36:47,760
sure um and he also says these are the

948
00:36:52,710 --> 00:36:49,599
first uh discrete carbon phases

949
00:36:56,069 --> 00:36:52,720
described on the apollo samples so he

950
00:36:57,430 --> 00:36:56,079
would know yes thank you steely um

951
00:36:59,670 --> 00:36:57,440
and and then we have another question

952
00:37:00,710 --> 00:36:59,680
here yes please yeah it's one for nathan

953
00:37:02,470 --> 00:37:00,720
um

954
00:37:04,310 --> 00:37:02,480
my understanding is people who model the

955
00:37:06,630 --> 00:37:04,320
ocean think that there are vanishingly

956
00:37:07,670 --> 00:37:06,640
low amounts of sulfate in the archaean

957
00:37:10,310 --> 00:37:07,680
ocean

958
00:37:12,069 --> 00:37:10,320
how does the model of the photo are you

959
00:37:14,550 --> 00:37:12,079
getting are you getting more than those

960
00:37:20,069 --> 00:37:14,560
low estimates with the modeling or or

961
00:37:25,190 --> 00:37:23,510
look um

962
00:37:27,349 --> 00:37:25,200
so there's been estimates of how much

963
00:37:29,510 --> 00:37:27,359
sulfate were in their key notions based

964
00:37:31,270 --> 00:37:29,520
on sulfur isotope measurements right uh

965
00:37:33,190 --> 00:37:31,280
so people have tried to calibrate uh

966
00:37:35,190 --> 00:37:33,200
using the sulfuric measurements to a

967
00:37:37,589 --> 00:37:35,200
concentration scale and we think there's

968
00:37:39,510 --> 00:37:37,599
about a thousand times less sulfate in

969
00:37:41,670 --> 00:37:39,520
the archaea oceans than there are in

970
00:37:44,069 --> 00:37:41,680
today's oceans it's around 30 micro

971
00:37:47,030 --> 00:37:44,079
molar um

972
00:37:48,550 --> 00:37:47,040
so uh even with that that amount uh

973
00:37:51,109 --> 00:37:48,560
there's still some controversy about the

974
00:37:52,470 --> 00:37:51,119
sources of that sulfate uh that

975
00:37:54,550 --> 00:37:52,480
concentration of sulfate and whether or

976
00:37:56,230 --> 00:37:54,560
not volcanic outgassing could be the

977
00:37:58,630 --> 00:37:56,240
sole contributor to

978
00:38:00,550 --> 00:37:58,640
to the uh sulfate sources one

979
00:38:03,430 --> 00:38:00,560
interesting observation by aydah stuken

980
00:38:06,390 --> 00:38:03,440
is that it looks like in the neoarkins

981
00:38:08,710 --> 00:38:06,400
the last part of the archaneon there was

982
00:38:11,829 --> 00:38:08,720
more and more um

983
00:38:14,069 --> 00:38:11,839
sulfur detected in sedimentary rocks

984
00:38:15,270 --> 00:38:14,079
um so there's been a there was a rise in

985
00:38:17,030 --> 00:38:15,280
this

986
00:38:19,190 --> 00:38:17,040
sulfate inventory in the oceans at that

987
00:38:20,870 --> 00:38:19,200
time and

988
00:38:22,790 --> 00:38:20,880
various uh

989
00:38:25,589 --> 00:38:22,800
people have invoked different

990
00:38:27,349 --> 00:38:25,599
uh ideas to explain why there was this

991
00:38:29,829 --> 00:38:27,359
increase in sulfate delivery to the

992
00:38:32,390 --> 00:38:29,839
oceans at that time one was

993
00:38:35,190 --> 00:38:32,400
the rise of atmospheric oxygen and

994
00:38:38,630 --> 00:38:35,200
another is the evolution of life on land

995
00:38:40,550 --> 00:38:38,640
to promote uh weathering and

996
00:38:41,910 --> 00:38:40,560
what we think was an important factor

997
00:38:42,790 --> 00:38:41,920
was just the fact that there was more

998
00:38:45,829 --> 00:38:42,800
land

999
00:38:48,310 --> 00:38:45,839
exposed sunlight could potentially

1000
00:38:49,990 --> 00:38:48,320
explain why there was a rise in sulfate

1001
00:38:51,910 --> 00:38:50,000
concentrations in the oceans at that

1002
00:38:54,150 --> 00:38:51,920
time well i i can't remember the numbers

1003
00:38:56,630 --> 00:38:54,160
on your graph but did you did you get to

1004
00:38:59,990 --> 00:38:56,640
modern levels of sulfur in in the ocean

1005
00:39:02,710 --> 00:39:00,000
in in the modeling at 3.2 or so or we're

1006
00:39:05,349 --> 00:39:02,720
still way short right so so we think

1007
00:39:07,270 --> 00:39:05,359
there were micro molar ranges of sulfate

1008
00:39:09,109 --> 00:39:07,280
in the oceans in the archaean

1009
00:39:10,950 --> 00:39:09,119
my experiments showed that there was

1010
00:39:12,790 --> 00:39:10,960
millimolar concentrations of sulfate

1011
00:39:18,630 --> 00:39:12,800
produced by this reaction

1012
00:39:22,790 --> 00:39:20,710
um awesome do we have any other

1013
00:39:24,390 --> 00:39:22,800
questions we have um probably time for

1014
00:39:26,829 --> 00:39:24,400
one or two more we've got three minutes

1015
00:39:29,670 --> 00:39:26,839
until our next

1016
00:39:31,430 --> 00:39:29,680
speaker if not you can i'll take a break

1017
00:39:33,510 --> 00:39:31,440
and have a sip of water i think that's

1018
00:39:40,550 --> 00:39:33,520
okay

1019
00:39:40,560 --> 00:39:43,910
just

1020
00:39:43,920 --> 00:39:47,430
yeah absolutely

1021
00:39:50,950 --> 00:39:49,190
so i have a question

1022
00:39:58,550 --> 00:39:50,960
is it

1023
00:40:02,870 --> 00:40:00,550
so um the gentleman in green from

1024
00:40:07,190 --> 00:40:02,880
stanford right you had a question i

1025
00:40:11,109 --> 00:40:09,510
so one of the things that i like to do

1026
00:40:14,470 --> 00:40:11,119
is try to reconcile all these different

1027
00:40:16,390 --> 00:40:14,480
data sets and so this is a slide that

1028
00:40:17,910 --> 00:40:16,400
i've shown in various publications that

1029
00:40:19,750 --> 00:40:17,920
shows the entire four and a half billion

1030
00:40:21,430 --> 00:40:19,760
year history of the earth and the moon

1031
00:40:22,950 --> 00:40:21,440
with some exceptions

1032
00:40:25,109 --> 00:40:22,960
so the curves that you see are actually

1033
00:40:27,430 --> 00:40:25,119
the impact fluxes that we've interpreted

1034
00:40:28,790 --> 00:40:27,440
from impact glasses lunar impact brushes

1035
00:40:31,030 --> 00:40:28,800
lunar meteorites and the asteroid

1036
00:40:32,630 --> 00:40:31,040
meteorites and then superimposed on

1037
00:40:34,710 --> 00:40:32,640
there are some of these biological and

1038
00:40:36,950 --> 00:40:34,720
geological events including that great

1039
00:40:39,829 --> 00:40:36,960
oxidation event that you asked about

1040
00:40:41,829 --> 00:40:39,839
and so you can see here that impacts as

1041
00:40:42,950 --> 00:40:41,839
inferred from the lunar and asteroidal

1042
00:40:44,230 --> 00:40:42,960
meteorite

1043
00:40:49,270 --> 00:40:44,240
inventory

1044
00:40:52,870 --> 00:40:49,280
were much reduced in that 3.5 to 2.0

1045
00:40:55,270 --> 00:40:52,880
billion year range where the goe

1046
00:40:56,309 --> 00:40:55,280
appears to to happen

1047
00:40:57,589 --> 00:40:56,319
so

1048
00:41:02,470 --> 00:40:57,599
this

1049
00:41:04,710 --> 00:41:02,480
reflects what monica described

1050
00:41:07,349 --> 00:41:04,720
that if impacts are actually suppressing

1051
00:41:08,710 --> 00:41:07,359
oxy oxygenation when you don't have

1052
00:41:11,990 --> 00:41:08,720
impacts you're going to start getting

1053
00:41:12,000 --> 00:41:18,309
awesome

1054
00:41:18,319 --> 00:41:32,630
so we can talk about it later

1055
00:41:39,430 --> 00:41:34,470
okay well i just wanted to put that out

1056
00:41:39,440 --> 00:41:43,430
oh okay

1057
00:41:48,550 --> 00:41:47,270
awesome and we are right at 3 40 um so i

1058
00:41:50,309 --> 00:41:48,560
think we can go ahead and start with our

1059
00:41:52,630 --> 00:41:50,319
next speaker and that is bob hazen from

1060
00:41:54,790 --> 00:41:52,640
the carnegie institution for science and

1061
00:41:56,069 --> 00:41:54,800
he's going to be talking to us

1062
00:41:57,750 --> 00:41:56,079
sorry click the wrong button he's going

1063
00:42:00,470 --> 00:41:57,760
to be talking to us about rare elements

1064
00:42:02,870 --> 00:42:00,480
and surface sites and rock forming

1065
00:42:06,309 --> 00:42:02,880
minerals

1066
00:42:10,870 --> 00:42:08,150
and

1067
00:42:12,309 --> 00:42:10,880
here we go in the hidden so thank you

1068
00:42:13,990 --> 00:42:12,319
bob

1069
00:42:15,670 --> 00:42:14,000
thank you so much shawna and all the

1070
00:42:17,109 --> 00:42:15,680
work i'm going to be describing was done

1071
00:42:19,349 --> 00:42:17,119
in collaboration with shauna at the

1072
00:42:21,510 --> 00:42:19,359
carnegie institution

1073
00:42:25,109 --> 00:42:21,520
so i'm really excited about talking

1074
00:42:26,870 --> 00:42:25,119
about aspects of mineralogical diversity

1075
00:42:29,270 --> 00:42:26,880
in the hidden era

1076
00:42:31,510 --> 00:42:29,280
and i have three sort of major points

1077
00:42:34,790 --> 00:42:31,520
that mineral surfaces as we all know

1078
00:42:37,030 --> 00:42:34,800
interact strongly with organic molecules

1079
00:42:38,870 --> 00:42:37,040
and one solution to problem of where

1080
00:42:41,030 --> 00:42:38,880
some of these interactions occurred has

1081
00:42:43,030 --> 00:42:41,040
to do with trace and minor elements

1082
00:42:45,030 --> 00:42:43,040
in rare minerals

1083
00:42:46,550 --> 00:42:45,040
and finally that we're going to show

1084
00:42:47,990 --> 00:42:46,560
that hidden mineralogy may have been

1085
00:42:49,990 --> 00:42:48,000
much more diverse than some of the

1086
00:42:51,829 --> 00:42:50,000
previous estimates

1087
00:42:53,510 --> 00:42:51,839
so we know minerals played essential

1088
00:42:55,750 --> 00:42:53,520
roles in the origin of life they

1089
00:42:57,030 --> 00:42:55,760
catalyzed reactions they acted as

1090
00:42:59,670 --> 00:42:57,040
scaffolding

1091
00:43:01,990 --> 00:42:59,680
they selected and concentrated molecules

1092
00:43:03,829 --> 00:43:02,000
on surfaces they were reactants they

1093
00:43:05,430 --> 00:43:03,839
were containers

1094
00:43:07,829 --> 00:43:05,440
and a lot of the work that's been

1095
00:43:09,670 --> 00:43:07,839
described recently has

1096
00:43:11,190 --> 00:43:09,680
invoked minerals in various ways and

1097
00:43:13,670 --> 00:43:11,200
some of them have invoked rather rare

1098
00:43:15,510 --> 00:43:13,680
minerals particularly the work of steve

1099
00:43:17,109 --> 00:43:15,520
benner and his group fascinating work

1100
00:43:19,750 --> 00:43:17,119
that talks about borates and

1101
00:43:22,069 --> 00:43:19,760
molybdenates some phosphorus compounds

1102
00:43:23,510 --> 00:43:22,079
i'm really sorry that tom orlando wasn't

1103
00:43:24,630 --> 00:43:23,520
here to talk about that because i think

1104
00:43:26,870 --> 00:43:24,640
there would have been

1105
00:43:27,829 --> 00:43:26,880
some overlap with what we're doing

1106
00:43:28,630 --> 00:43:27,839
and

1107
00:43:30,630 --> 00:43:28,640
we

1108
00:43:32,069 --> 00:43:30,640
in the last few years have published

1109
00:43:35,190 --> 00:43:32,079
lists of what we think might have been

1110
00:43:38,150 --> 00:43:35,200
plausible hidean minerals

1111
00:43:40,069 --> 00:43:38,160
revising those lists in various ways and

1112
00:43:41,750 --> 00:43:40,079
what we see is that the commonest

1113
00:43:43,270 --> 00:43:41,760
minerals that are invoked sulfides and

1114
00:43:45,109 --> 00:43:43,280
clay minerals and carbonates are

1115
00:43:46,790 --> 00:43:45,119
certainly there but certain other

1116
00:43:49,510 --> 00:43:46,800
minerals like borates and militates

1117
00:43:51,510 --> 00:43:49,520
would have been vanishingly rare

1118
00:43:53,190 --> 00:43:51,520
and so one solution to this problem is

1119
00:43:55,829 --> 00:43:53,200
the idea of using trace and minor

1120
00:43:58,710 --> 00:43:55,839
elements basically as dopants

1121
00:44:00,710 --> 00:43:58,720
in common rock forming minerals

1122
00:44:02,790 --> 00:44:00,720
and i think that this was there are many

1123
00:44:04,309 --> 00:44:02,800
many papers that sort of explore aspects

1124
00:44:06,950 --> 00:44:04,319
of this there was a beautiful paper this

1125
00:44:09,670 --> 00:44:06,960
morning by rachel speaks who

1126
00:44:11,990 --> 00:44:09,680
showed that the small amounts of nickel

1127
00:44:14,309 --> 00:44:12,000
in pyrite can greatly enhance the

1128
00:44:17,190 --> 00:44:14,319
metabolic rates of methanogens so that

1129
00:44:19,910 --> 00:44:17,200
type of discovery i think points to the

1130
00:44:21,990 --> 00:44:19,920
role of dopants and here's our idea the

1131
00:44:24,390 --> 00:44:22,000
scores of trace and minor elements are

1132
00:44:26,950 --> 00:44:24,400
ubiquitous in the commonest rock forming

1133
00:44:29,190 --> 00:44:26,960
minerals and also talk about the mineral

1134
00:44:31,430 --> 00:44:29,200
diversity later on in this talk so here

1135
00:44:33,910 --> 00:44:31,440
is a table from a paper that's just come

1136
00:44:37,109 --> 00:44:33,920
out and i'm happy to share this with you

1137
00:44:39,510 --> 00:44:37,119
if you want what we did is we looked at

1138
00:44:42,150 --> 00:44:39,520
some of those rare elements that don't

1139
00:44:43,109 --> 00:44:42,160
form a volumetrically very many minerals

1140
00:44:44,630 --> 00:44:43,119
at all

1141
00:44:47,190 --> 00:44:44,640
yet they're present in the crust and

1142
00:44:48,710 --> 00:44:47,200
significant amounts and if you look at

1143
00:44:51,430 --> 00:44:48,720
the commonest rock foreign minerals

1144
00:44:53,829 --> 00:44:51,440
olivine pyroxene feldspar you'll see

1145
00:44:55,990 --> 00:44:53,839
orders of magnitude increase in some

1146
00:44:57,750 --> 00:44:56,000
cases in the concentration

1147
00:45:00,470 --> 00:44:57,760
in these minerals that were ubiquitous

1148
00:45:02,870 --> 00:45:00,480
for example in ocean floor basalts

1149
00:45:04,790 --> 00:45:02,880
and and so even though you may not have

1150
00:45:07,990 --> 00:45:04,800
a mineral that

1151
00:45:10,630 --> 00:45:08,000
specifically has nickel or vanadium or

1152
00:45:12,790 --> 00:45:10,640
copper as a major element

1153
00:45:15,430 --> 00:45:12,800
still these elements have been available

1154
00:45:17,670 --> 00:45:15,440
abundantly in various surfaces for kinds

1155
00:45:19,670 --> 00:45:17,680
of reactions that we see have been used

1156
00:45:21,510 --> 00:45:19,680
in prebiotic models

1157
00:45:23,109 --> 00:45:21,520
so our conclusion for the first part of

1158
00:45:24,870 --> 00:45:23,119
this talk is that these potentially

1159
00:45:27,190 --> 00:45:24,880
important minerals while they're not

1160
00:45:29,589 --> 00:45:27,200
replaced represented by common minerals

1161
00:45:31,349 --> 00:45:29,599
they are certainly widely available

1162
00:45:33,270 --> 00:45:31,359
in rock forming minerals

1163
00:45:35,990 --> 00:45:33,280
all across earth's surface

1164
00:45:38,630 --> 00:45:36,000
now you might ask i asked myself how can

1165
00:45:40,950 --> 00:45:38,640
i miss this obvious point and the answer

1166
00:45:42,870 --> 00:45:40,960
really lies in the definition of mineral

1167
00:45:44,550 --> 00:45:42,880
species so what i want to do is

1168
00:45:47,109 --> 00:45:44,560
describe a new way of thinking about

1169
00:45:49,109 --> 00:45:47,119
minerals and mineral kinds

1170
00:45:50,790 --> 00:45:49,119
the ima international mineralogical

1171
00:45:53,190 --> 00:45:50,800
association defines minerals as

1172
00:45:55,190 --> 00:45:53,200
naturally occurring crystals

1173
00:45:56,710 --> 00:45:55,200
they have an idealized n-member

1174
00:45:58,870 --> 00:45:56,720
composition they have an idealized

1175
00:46:00,710 --> 00:45:58,880
structure any combination that's unique

1176
00:46:03,349 --> 00:46:00,720
of that structure and member composition

1177
00:46:06,390 --> 00:46:03,359
is a species they're about 5700 almost

1178
00:46:08,390 --> 00:46:06,400
5800 mineral species today and what the

1179
00:46:10,309 --> 00:46:08,400
ima is doing is basically a very

1180
00:46:12,069 --> 00:46:10,319
efficient system that uses the absolute

1181
00:46:15,109 --> 00:46:12,079
minimum amount of information to

1182
00:46:17,190 --> 00:46:15,119
distinguish one mineral from another but

1183
00:46:19,190 --> 00:46:17,200
the fundamental aspect of all minerals

1184
00:46:20,630 --> 00:46:19,200
is they're incredibly information rich

1185
00:46:23,270 --> 00:46:20,640
they have trace and minor elements they

1186
00:46:24,630 --> 00:46:23,280
have isotopes defects inclusions all

1187
00:46:27,030 --> 00:46:24,640
sorts of other things that tell the

1188
00:46:29,510 --> 00:46:27,040
history of each individual sample and we

1189
00:46:32,069 --> 00:46:29,520
want to embrace that so what we do in

1190
00:46:33,030 --> 00:46:32,079
our new system of mineralogy

1191
00:46:35,510 --> 00:46:33,040
is

1192
00:46:37,910 --> 00:46:35,520
we split some ima species into several

1193
00:46:40,230 --> 00:46:37,920
natural kinds we lump other species into

1194
00:46:42,550 --> 00:46:40,240
one natural kind and we also recognize

1195
00:46:44,950 --> 00:46:42,560
amorphous materials which are not

1196
00:46:47,349 --> 00:46:44,960
treated by the ima system and what this

1197
00:46:49,670 --> 00:46:47,359
means is in some cases like pyrite there

1198
00:46:51,430 --> 00:46:49,680
can be many natural kinds more than 20

1199
00:46:52,710 --> 00:46:51,440
in the case of pyrite some are high

1200
00:46:55,349 --> 00:46:52,720
temperatures some are low temperatures

1201
00:46:57,990 --> 00:46:55,359
some are biotic some are abiotic and so

1202
00:47:00,550 --> 00:46:58,000
forth but in other cases like tourmaline

1203
00:47:02,950 --> 00:47:00,560
where ima recognizes more than 35

1204
00:47:04,710 --> 00:47:02,960
different species of tourmaline

1205
00:47:07,349 --> 00:47:04,720
in one of these crystals you can have

1206
00:47:09,589 --> 00:47:07,359
seven different ima species in a single

1207
00:47:11,190 --> 00:47:09,599
crystal because of zoning we say no

1208
00:47:13,030 --> 00:47:11,200
that's just one natural kind and there's

1209
00:47:15,109 --> 00:47:13,040
probably only two or three natural kinds

1210
00:47:17,510 --> 00:47:15,119
of tourmaline all together and we also

1211
00:47:19,589 --> 00:47:17,520
embrace as i said amorphous materials

1212
00:47:21,990 --> 00:47:19,599
volcanic glasses and other sorts of

1213
00:47:23,990 --> 00:47:22,000
amorphous materials that in some cases

1214
00:47:26,950 --> 00:47:24,000
for example the lunar

1215
00:47:29,349 --> 00:47:26,960
the martian regolith this is really

1216
00:47:31,270 --> 00:47:29,359
important 50 or more of most martian

1217
00:47:32,950 --> 00:47:31,280
soils or amorphous materials and you

1218
00:47:35,030 --> 00:47:32,960
can't really understand the evolution of

1219
00:47:37,109 --> 00:47:35,040
mars without understanding those

1220
00:47:39,190 --> 00:47:37,119
amorphous materials so we've begun an

1221
00:47:42,150 --> 00:47:39,200
evolutionary system in mineralogy we use

1222
00:47:44,069 --> 00:47:42,160
a binomial nomenclature where we have a

1223
00:47:45,829 --> 00:47:44,079
mineral like graphite linked to its

1224
00:47:49,270 --> 00:47:45,839
formational environment for example the

1225
00:47:52,309 --> 00:47:49,280
type 2 supernova here is agb moissanite

1226
00:47:54,309 --> 00:47:52,319
agb stars in which moissanite forms we

1227
00:47:56,630 --> 00:47:54,319
use network graphs helped by our

1228
00:47:58,790 --> 00:47:56,640
colleague underwood prabhu in which we

1229
00:48:01,270 --> 00:47:58,800
have two different kinds of nodes some

1230
00:48:03,510 --> 00:48:01,280
nodes represent formational environments

1231
00:48:06,630 --> 00:48:03,520
some nodes represent mineral species and

1232
00:48:08,950 --> 00:48:06,640
every link then is a binomial natural

1233
00:48:10,870 --> 00:48:08,960
kind of a mineral so here's the first

1234
00:48:13,750 --> 00:48:10,880
network we can expand that to include

1235
00:48:15,990 --> 00:48:13,760
solar condensates and cais

1236
00:48:17,589 --> 00:48:16,000
here's interstellar clouds we can expand

1237
00:48:19,910 --> 00:48:17,599
it going on these are the primary

1238
00:48:22,309 --> 00:48:19,920
chondrol minerals those igneous minerals

1239
00:48:24,630 --> 00:48:22,319
in the early solar system

1240
00:48:26,710 --> 00:48:24,640
the different alteration products impact

1241
00:48:29,349 --> 00:48:26,720
aqueous thermal alteration products we

1242
00:48:31,750 --> 00:48:29,359
see the network expanding and expanding

1243
00:48:33,990 --> 00:48:31,760
our model for earliest hidden mineralogy

1244
00:48:36,150 --> 00:48:34,000
came in part six of the evolutionary

1245
00:48:38,309 --> 00:48:36,160
system which is now in press

1246
00:48:39,990 --> 00:48:38,319
you'll notice that there is the original

1247
00:48:42,069 --> 00:48:40,000
network that i showed you of the stellar

1248
00:48:44,390 --> 00:48:42,079
minerals it's still embedded in this

1249
00:48:46,829 --> 00:48:44,400
larger expanding network

1250
00:48:49,829 --> 00:48:46,839
we also think that this network is a

1251
00:48:52,230 --> 00:48:49,839
reasonable model of martian uh yeah

1252
00:48:53,589 --> 00:48:52,240
martian mineralogy today

1253
00:48:55,510 --> 00:48:53,599
that's something that's a testable

1254
00:48:58,069 --> 00:48:55,520
hypothesis but it looks like mars got

1255
00:49:01,670 --> 00:48:58,079
about this far and fast forwarding to

1256
00:49:03,750 --> 00:49:01,680
our network of all 5700 minerals more

1257
00:49:06,630 --> 00:49:03,760
than 60 different ways of forming those

1258
00:49:08,950 --> 00:49:06,640
minerals forming a network which reveals

1259
00:49:11,109 --> 00:49:08,960
all sorts of indications about how

1260
00:49:13,829 --> 00:49:11,119
minerals diversified through time and

1261
00:49:15,190 --> 00:49:13,839
reveals that by the mid hidden certainly

1262
00:49:17,910 --> 00:49:15,200
by the end of the hadith there probably

1263
00:49:19,670 --> 00:49:17,920
were 2 000 mineral species so many many

1264
00:49:22,230 --> 00:49:19,680
more minerals to play around with in

1265
00:49:24,390 --> 00:49:22,240
your prebiotic chemistry

1266
00:49:26,549 --> 00:49:24,400
i want to make just a couple conclusions

1267
00:49:28,549 --> 00:49:26,559
one of them that was very dramatic is at

1268
00:49:30,150 --> 00:49:28,559
least 80 percent of minerals on earth

1269
00:49:32,069 --> 00:49:30,160
maybe it's as much as 90 percent

1270
00:49:34,230 --> 00:49:32,079
depending on how you count depend on

1271
00:49:36,150 --> 00:49:34,240
water they would not form without water

1272
00:49:38,390 --> 00:49:36,160
rock interactions

1273
00:49:40,309 --> 00:49:38,400
biology also is incredibly important on

1274
00:49:42,630 --> 00:49:40,319
earth for mineral diversification fully

1275
00:49:44,790 --> 00:49:42,640
half of all minerals on earth can form

1276
00:49:47,109 --> 00:49:44,800
through biological processes and a third

1277
00:49:49,510 --> 00:49:47,119
of minerals on earth form exclusively

1278
00:49:51,109 --> 00:49:49,520
through biological processes

1279
00:49:53,030 --> 00:49:51,119
so our conclusions

1280
00:49:55,349 --> 00:49:53,040
mineral molecule interactions of course

1281
00:49:57,750 --> 00:49:55,359
played key roles in life's origin and we

1282
00:50:00,390 --> 00:49:57,760
can use the trace and minor elements and

1283
00:50:02,710 --> 00:50:00,400
common rock forming minerals to help

1284
00:50:04,390 --> 00:50:02,720
catalyze some of those reactions

1285
00:50:06,870 --> 00:50:04,400
a lot of experiments need to be done to

1286
00:50:09,030 --> 00:50:06,880
test these ideas and the evolutionary

1287
00:50:11,670 --> 00:50:09,040
system in mineralogy is pointing out

1288
00:50:14,150 --> 00:50:11,680
that earth's mineralogy diversified much

1289
00:50:15,670 --> 00:50:14,160
earlier than previously suggested

1290
00:50:17,990 --> 00:50:15,680
and finally i just want to make this

1291
00:50:19,990 --> 00:50:18,000
comment about we think about is is life

1292
00:50:21,589 --> 00:50:20,000
a deterministic process well this

1293
00:50:23,430 --> 00:50:21,599
realization that these common rock

1294
00:50:25,910 --> 00:50:23,440
foreign minerals host rich diversities

1295
00:50:28,390 --> 00:50:25,920
of reactive surfaces almost any kind of

1296
00:50:30,150 --> 00:50:28,400
reactive site you might want occurs on

1297
00:50:32,710 --> 00:50:30,160
some prebiotic mineral

1298
00:50:34,390 --> 00:50:32,720
that this leads to

1299
00:50:37,430 --> 00:50:34,400
support the idea of a robust

1300
00:50:39,349 --> 00:50:37,440
deterministic prebiotic chemical mule

1301
00:50:42,069 --> 00:50:39,359
year with that i want to thank my

1302
00:50:43,510 --> 00:50:42,079
funding agencies thanks shauna again for

1303
00:50:45,910 --> 00:50:43,520
the great collaborations we've been

1304
00:50:47,270 --> 00:50:45,920
having and maybe we'll have time for a

1305
00:50:53,349 --> 00:50:47,280
question i don't know

1306
00:50:55,990 --> 00:50:54,549
yeah

1307
00:50:58,150 --> 00:50:56,000
we absolutely do have time for a

1308
00:51:00,870 --> 00:50:58,160
question so go ahead hi there bob great

1309
00:51:02,710 --> 00:51:00,880
talk thanks uh harry from cu boulder i'm

1310
00:51:04,549 --> 00:51:02,720
wondering given the absence of these

1311
00:51:06,309 --> 00:51:04,559
rare element minerals do you think the

1312
00:51:09,190 --> 00:51:06,319
other minerals would have been even more

1313
00:51:10,950 --> 00:51:09,200
enriched in these rare dopants

1314
00:51:13,430 --> 00:51:10,960
what we see in the rock-forming minerals

1315
00:51:15,589 --> 00:51:13,440
is they always have these rare elements

1316
00:51:17,750 --> 00:51:15,599
in them to some extent pyroxene always

1317
00:51:20,069 --> 00:51:17,760
concentrates the the other transition

1318
00:51:21,829 --> 00:51:20,079
elements for example and certainly if

1319
00:51:23,670 --> 00:51:21,839
they were not being swallowed up by

1320
00:51:25,430 --> 00:51:23,680
other rare minerals it might be greater

1321
00:51:27,349 --> 00:51:25,440
but i should make the point cobalt for

1322
00:51:29,430 --> 00:51:27,359
example if you take all the cobalt

1323
00:51:31,510 --> 00:51:29,440
minerals on earth and look at their

1324
00:51:34,470 --> 00:51:31,520
volume it's 1

1325
00:51:38,390 --> 00:51:34,480
50 millionth of the amount of cobalt

1326
00:51:40,150 --> 00:51:38,400
that's in basalt

1327
00:51:41,750 --> 00:51:40,160
so there's a lot of basalt and so

1328
00:51:44,390 --> 00:51:41,760
there's a lot of cobalt even though it's

1329
00:51:46,549 --> 00:51:44,400
a trace element got it thanks

1330
00:51:48,390 --> 00:51:46,559
and i think we have time for one more

1331
00:51:50,950 --> 00:51:48,400
fine i guess it's pretty quick uh matt

1332
00:51:52,470 --> 00:51:50,960
from stanford again um so question what

1333
00:51:54,950 --> 00:51:52,480
you were saying so it seemed like there

1334
00:51:57,510 --> 00:51:54,960
was fewer minerals in the distant past

1335
00:51:59,349 --> 00:51:57,520
and we've gained more over time

1336
00:52:01,109 --> 00:51:59,359
is it so in the future there should be

1337
00:52:02,870 --> 00:52:01,119
new minerals

1338
00:52:04,950 --> 00:52:02,880
that don't exist today

1339
00:52:06,230 --> 00:52:04,960
can you theoretically predict what they

1340
00:52:07,670 --> 00:52:06,240
might be

1341
00:52:09,349 --> 00:52:07,680
yes we've been doing this in a field

1342
00:52:11,109 --> 00:52:09,359
called mineral ecology which is which

1343
00:52:12,549 --> 00:52:11,119
another whole talk is a lot of fun also

1344
00:52:15,030 --> 00:52:12,559
of course there's the anthropogenic

1345
00:52:16,309 --> 00:52:15,040
signal and in terms of mineral-like

1346
00:52:18,870 --> 00:52:16,319
compounds

1347
00:52:20,390 --> 00:52:18,880
there are literally hundreds of of

1348
00:52:23,910 --> 00:52:20,400
minerals

1349
00:52:26,549 --> 00:52:23,920
that human mining human engineering

1350
00:52:28,069 --> 00:52:26,559
human waste dumps are forming and those

1351
00:52:30,390 --> 00:52:28,079
will be a permanent part of the

1352
00:52:32,630 --> 00:52:30,400
geological record for many hundreds of

1353
00:52:34,710 --> 00:52:32,640
millions of years in in cases laser

1354
00:52:37,270 --> 00:52:34,720
crystals things like that they just go

1355
00:52:40,069 --> 00:52:37,280
into waste stumps and and so indeed the

1356
00:52:42,950 --> 00:52:40,079
diversification is increasing at an ever

1357
00:52:44,470 --> 00:52:42,960
uh more rapid rate

1358
00:52:45,750 --> 00:52:44,480
and then there's one quick question

1359
00:52:47,190 --> 00:52:45,760
online that shouldn't take too long and

1360
00:52:48,790 --> 00:52:47,200
that's from jyn glass and she asks is

1361
00:52:50,309 --> 00:52:48,800
the chemical speciation of the minor

1362
00:52:52,309 --> 00:52:50,319
elements and the major rock forming

1363
00:52:54,790 --> 00:52:52,319
minerals the necessary form for

1364
00:52:57,190 --> 00:52:54,800
prebiotic chemistry eg previous theories

1365
00:52:59,589 --> 00:52:57,200
about oxidizing hi jen thanks for that

1366
00:53:01,510 --> 00:52:59,599
question and indeed

1367
00:53:04,230 --> 00:53:01,520
we think that there are many many

1368
00:53:05,990 --> 00:53:04,240
different speciations of these rare

1369
00:53:07,750 --> 00:53:06,000
elements in rock forming minerals

1370
00:53:09,270 --> 00:53:07,760
they're different kinds of surface sites

1371
00:53:10,230 --> 00:53:09,280
there's different kinds of oxidation

1372
00:53:12,790 --> 00:53:10,240
states

1373
00:53:14,230 --> 00:53:12,800
and virtually any configuration you can

1374
00:53:16,390 --> 00:53:14,240
imagine that you want any kind of

1375
00:53:18,549 --> 00:53:16,400
complexation on the surface or even

1376
00:53:20,630 --> 00:53:18,559
dissolution in forming some kind of

1377
00:53:22,390 --> 00:53:20,640
aqueous species

1378
00:53:23,589 --> 00:53:22,400
we think that this provides a very

1379
00:53:25,829 --> 00:53:23,599
robust

1380
00:53:27,750 --> 00:53:25,839
so so pick your favorite

1381
00:53:29,750 --> 00:53:27,760
oxidation state pick your favorite

1382
00:53:31,829 --> 00:53:29,760
configuration and you probably can have

1383
00:53:34,080 --> 00:53:31,839
it if you want it

1384
00:53:38,069 --> 00:53:34,090
thank you bob let's give bob a hand

1385
00:53:42,470 --> 00:53:40,549
and up next we have one of our two

1386
00:53:45,109 --> 00:53:42,480
invited speakers and of course that's

1387
00:53:46,790 --> 00:53:45,119
raj das gupta from rice university and

1388
00:53:49,510 --> 00:53:46,800
he's going to be talking to us about the

1389
00:53:52,150 --> 00:53:49,520
origin of life essential uh volatile

1390
00:53:54,870 --> 00:53:52,160
elements on earth thank you raj

1391
00:53:56,950 --> 00:53:54,880
thanks shauna for the invitation so here

1392
00:53:58,630 --> 00:53:56,960
i'll be talking about uh the origin of

1393
00:54:00,870 --> 00:53:58,640
life essential volatile elements on

1394
00:54:03,109 --> 00:54:00,880
earth and this is a collaborative work

1395
00:54:04,790 --> 00:54:03,119
that uh we have been doing with our

1396
00:54:07,349 --> 00:54:04,800
former student daman gravel barnard

1397
00:54:09,829 --> 00:54:07,359
marty and undergrad students taylor half

1398
00:54:12,069 --> 00:54:09,839
high school student alexander farnell

1399
00:54:13,990 --> 00:54:12,079
and this is part of the clever planets

1400
00:54:17,670 --> 00:54:14,000
initiative that was funded by nasa

1401
00:54:20,950 --> 00:54:17,680
astrology institute called can um eight

1402
00:54:23,349 --> 00:54:20,960
and we are based out of rice university

1403
00:54:26,150 --> 00:54:23,359
so um this is not a news to the audience

1404
00:54:28,710 --> 00:54:26,160
here all organisms are built from the

1405
00:54:31,030 --> 00:54:28,720
same six essential elements or elemental

1406
00:54:33,510 --> 00:54:31,040
ingredients and they are carbon hydrogen

1407
00:54:36,630 --> 00:54:33,520
nitrogen oxygen phosphorus and sulfur

1408
00:54:39,910 --> 00:54:36,640
um actually 98 percent or more than 98

1409
00:54:41,430 --> 00:54:39,920
of all organisms are built out of these

1410
00:54:43,750 --> 00:54:41,440
key elements and especially if you look

1411
00:54:46,150 --> 00:54:43,760
at carbon hydrogen and nitrogen they are

1412
00:54:48,309 --> 00:54:46,160
the true building blocks of

1413
00:54:50,150 --> 00:54:48,319
nucleotide the base and the and the

1414
00:54:52,950 --> 00:54:50,160
sugar and everything right so the

1415
00:54:54,950 --> 00:54:52,960
question is uh what supplies these key

1416
00:54:57,990 --> 00:54:54,960
life essential elements at the surface

1417
00:55:00,150 --> 00:54:58,000
environment of rocky planets

1418
00:55:01,829 --> 00:55:00,160
although these are the key elements

1419
00:55:03,670 --> 00:55:01,839
that are needed for making life at the

1420
00:55:06,150 --> 00:55:03,680
surface of rocky planets their

1421
00:55:08,230 --> 00:55:06,160
availability at the surface really

1422
00:55:11,510 --> 00:55:08,240
relies on the permission from the

1423
00:55:14,230 --> 00:55:11,520
interior of our planet these key gases

1424
00:55:16,470 --> 00:55:14,240
are the key elements available for life

1425
00:55:18,230 --> 00:55:16,480
actually are available uh by the

1426
00:55:19,990 --> 00:55:18,240
permission of the mantle because

1427
00:55:22,710 --> 00:55:20,000
volcanic degassing releases these

1428
00:55:24,630 --> 00:55:22,720
elements to the surface uh for

1429
00:55:26,230 --> 00:55:24,640
earth and as you have already heard

1430
00:55:28,710 --> 00:55:26,240
probably some sort of a plate tectonic

1431
00:55:31,670 --> 00:55:28,720
cycle started as early as 3.8 or 4

1432
00:55:33,510 --> 00:55:31,680
billion years ago so these uh cycles can

1433
00:55:36,069 --> 00:55:33,520
also sequester these elements into the

1434
00:55:38,150 --> 00:55:36,079
interior so in order to understand how

1435
00:55:40,870 --> 00:55:38,160
we have these elements at the surface we

1436
00:55:43,349 --> 00:55:40,880
truly need to be understanding how we

1437
00:55:45,990 --> 00:55:43,359
have these elements uh in the bulk

1438
00:55:47,990 --> 00:55:46,000
silicate earth of our planet meaning the

1439
00:55:49,990 --> 00:55:48,000
surface reservoirs the atmosphere as

1440
00:55:52,230 --> 00:55:50,000
well as the silicate reservoirs that are

1441
00:55:54,390 --> 00:55:52,240
in constant communication over millions

1442
00:55:56,309 --> 00:55:54,400
of years and billions of years right so

1443
00:55:58,390 --> 00:55:56,319
what we are interested in in this talk

1444
00:55:59,829 --> 00:55:58,400
is figuring out what's the origin of

1445
00:56:01,589 --> 00:55:59,839
some of these key life essential

1446
00:56:04,150 --> 00:56:01,599
volatile elements in the bulk silicate

1447
00:56:05,750 --> 00:56:04,160
earth meaning the surface inventory is

1448
00:56:07,589 --> 00:56:05,760
the atmosphere

1449
00:56:10,390 --> 00:56:07,599
and the silicate mantle meaning

1450
00:56:12,069 --> 00:56:10,400
everything in our planet minus the core

1451
00:56:14,309 --> 00:56:12,079
which is the metallic portion of our

1452
00:56:16,309 --> 00:56:14,319
planet

1453
00:56:19,270 --> 00:56:16,319
and actually uh one of the recent

1454
00:56:21,670 --> 00:56:19,280
studies uh by god guyard and others and

1455
00:56:24,150 --> 00:56:21,680
that i'm showing here argued that

1456
00:56:26,549 --> 00:56:24,160
elements such as nitrogen carbon and

1457
00:56:29,109 --> 00:56:26,559
hydrogen their surfacial abundance

1458
00:56:30,870 --> 00:56:29,119
includes including their atmospheric

1459
00:56:33,670 --> 00:56:30,880
partial pressures could have been

1460
00:56:35,510 --> 00:56:33,680
actually um established as early right

1461
00:56:37,430 --> 00:56:35,520
after the moon farming impact by magma

1462
00:56:39,589 --> 00:56:37,440
ocean degassing so meaning at that

1463
00:56:41,990 --> 00:56:39,599
period of our planet the planet was

1464
00:56:44,549 --> 00:56:42,000
mostly molten and the degassing of that

1465
00:56:46,630 --> 00:56:44,559
silicate molten silicate could supply

1466
00:56:49,190 --> 00:56:46,640
all these elements into the surface so

1467
00:56:51,430 --> 00:56:49,200
the question is um how did the magma

1468
00:56:53,270 --> 00:56:51,440
motion or that final silicate mass of

1469
00:56:55,430 --> 00:56:53,280
our planet right before the magnesium

1470
00:56:57,109 --> 00:56:55,440
crystallization acquired these key

1471
00:56:59,430 --> 00:56:57,119
elements

1472
00:57:01,750 --> 00:56:59,440
um actually interestingly all of these

1473
00:57:03,990 --> 00:57:01,760
elements are heavily depleted in our

1474
00:57:05,430 --> 00:57:04,000
planet so if you compare with the

1475
00:57:08,549 --> 00:57:05,440
nominal building blocks such as

1476
00:57:10,549 --> 00:57:08,559
chondrite you will see that um bulk

1477
00:57:12,630 --> 00:57:10,559
silicate earth is severely depleted in

1478
00:57:14,230 --> 00:57:12,640
elements such as carbon and nitrogen and

1479
00:57:15,670 --> 00:57:14,240
specifically speaking nitrogen is

1480
00:57:18,549 --> 00:57:15,680
heavily depleted

1481
00:57:21,430 --> 00:57:18,559
compared to carbon and sulfur and so on

1482
00:57:23,030 --> 00:57:21,440
so what this suggests especially the not

1483
00:57:24,630 --> 00:57:23,040
only just the absolute depletion but the

1484
00:57:26,309 --> 00:57:24,640
relative depletion with respect to

1485
00:57:27,910 --> 00:57:26,319
chondrite it suggests that post

1486
00:57:30,230 --> 00:57:27,920
differentiation meaning post code

1487
00:57:32,230 --> 00:57:30,240
formation post atmosphere formation

1488
00:57:33,910 --> 00:57:32,240
addition of quadratic meteorites cannot

1489
00:57:35,990 --> 00:57:33,920
actually explain the abundance or the

1490
00:57:37,750 --> 00:57:36,000
relative abundances of these key life

1491
00:57:39,990 --> 00:57:37,760
essential elements such as carbon and

1492
00:57:42,789 --> 00:57:40,000
nitrogen and sulfur because they are not

1493
00:57:45,109 --> 00:57:42,799
in conductive proportion

1494
00:57:47,109 --> 00:57:45,119
so what we want to do uh quickly in this

1495
00:57:48,710 --> 00:57:47,119
talk because we don't have a lot of time

1496
00:57:50,630 --> 00:57:48,720
instead of talking about all the key

1497
00:57:53,510 --> 00:57:50,640
life essential volatile elements we are

1498
00:57:55,510 --> 00:57:53,520
going to take lessons from nitrogen and

1499
00:57:57,829 --> 00:57:55,520
i am just going to quickly go through

1500
00:58:00,230 --> 00:57:57,839
snippets from two recent studies that we

1501
00:58:01,990 --> 00:58:00,240
did in our group uh one is about the

1502
00:58:03,910 --> 00:58:02,000
source of nitrogen meaning where did the

1503
00:58:05,990 --> 00:58:03,920
nitrogen from for the silicate and the

1504
00:58:07,750 --> 00:58:06,000
surfacial earth potentially come from

1505
00:58:09,910 --> 00:58:07,760
and what was the processes and the

1506
00:58:11,990 --> 00:58:09,920
timing of establishing that nitrogen

1507
00:58:15,270 --> 00:58:12,000
budget for the bulk silicate earth that

1508
00:58:17,109 --> 00:58:15,280
eventually uh gave uh supply of nitrogen

1509
00:58:19,109 --> 00:58:17,119
to the surface

1510
00:58:20,789 --> 00:58:19,119
uh so as i said quadratic material

1511
00:58:22,470 --> 00:58:20,799
addition cannot really explain nitrogen

1512
00:58:23,829 --> 00:58:22,480
or carbon to nitrogen relative

1513
00:58:25,510 --> 00:58:23,839
abundances because they are not in

1514
00:58:28,150 --> 00:58:25,520
quadratic proportions but one

1515
00:58:29,270 --> 00:58:28,160
interesting thing to realize is if you

1516
00:58:31,910 --> 00:58:29,280
look at

1517
00:58:33,910 --> 00:58:31,920
the entire history right from the onset

1518
00:58:35,670 --> 00:58:33,920
of solar system formation

1519
00:58:37,589 --> 00:58:35,680
the differentiation process meaning

1520
00:58:40,069 --> 00:58:37,599
separation of metals and silicates and

1521
00:58:42,390 --> 00:58:40,079
formation of proto-atmosphere started

1522
00:58:44,069 --> 00:58:42,400
very very early not just in a large

1523
00:58:46,870 --> 00:58:44,079
planet like ours but that type of

1524
00:58:49,430 --> 00:58:46,880
process started through a

1525
00:58:51,510 --> 00:58:49,440
radioactive decay of aluminum 26

1526
00:58:53,510 --> 00:58:51,520
supplying heat so melting and

1527
00:58:56,150 --> 00:58:53,520
differentiation of protoplanetary bodies

1528
00:58:57,430 --> 00:58:56,160
started very very early within sort of

1529
00:58:59,430 --> 00:58:57,440
less than a million year of the

1530
00:59:01,270 --> 00:58:59,440
formation of the solar system so when we

1531
00:59:03,270 --> 00:59:01,280
are going to think about building blocks

1532
00:59:04,710 --> 00:59:03,280
of earth like planet we shouldn't be

1533
00:59:06,630 --> 00:59:04,720
thinking only about this

1534
00:59:08,630 --> 00:59:06,640
undifferentiated meteorite delivery but

1535
00:59:10,470 --> 00:59:08,640
delivery of all these life essential

1536
00:59:11,829 --> 00:59:10,480
elements through addition of

1537
00:59:13,750 --> 00:59:11,839
differentiated objects through

1538
00:59:15,270 --> 00:59:13,760
protoplanets through planetary embryos

1539
00:59:17,670 --> 00:59:15,280
and so on

1540
00:59:20,630 --> 00:59:17,680
so with that framework in mind what we

1541
00:59:22,549 --> 00:59:20,640
did in this study in 2021 that came out

1542
00:59:24,630 --> 00:59:22,559
and came out in nature astronomy we

1543
00:59:26,870 --> 00:59:24,640
looked at iron meteorites and the reason

1544
00:59:28,630 --> 00:59:26,880
we looked at iron meteorites are for

1545
00:59:30,789 --> 00:59:28,640
three reasons one

1546
00:59:32,789 --> 00:59:30,799
iron meteorite parent bodies are some of

1547
00:59:34,390 --> 00:59:32,799
the earliest formed protoplanets that

1548
00:59:36,069 --> 00:59:34,400
underwent differentiation

1549
00:59:38,230 --> 00:59:36,079
protoplanetary differentiation for these

1550
00:59:40,230 --> 00:59:38,240
type of bodies happened as early as 0.3

1551
00:59:41,510 --> 00:59:40,240
million year within the formation of the

1552
00:59:43,670 --> 00:59:41,520
solar system

1553
00:59:46,150 --> 00:59:43,680
nitrogen or these volatile elements are

1554
00:59:47,990 --> 00:59:46,160
well preserved in irons unlike

1555
00:59:49,829 --> 00:59:48,000
alteration induced changes that can

1556
00:59:51,589 --> 00:59:49,839
happen in silicate type of meteorites

1557
00:59:54,470 --> 00:59:51,599
irons are much more refractory in that

1558
00:59:56,390 --> 00:59:54,480
sense and not only that through

1559
00:59:57,589 --> 00:59:56,400
studies of nuclear synthetic anomalies

1560
01:00:00,390 --> 00:59:57,599
of many different elements such as

1561
01:00:01,910 --> 01:00:00,400
nickel tungsten molybdenum ruthenium we

1562
01:00:03,510 --> 01:00:01,920
know iron meteorite brain body

1563
01:00:05,430 --> 01:00:03,520
differentiation took place both in the

1564
01:00:07,589 --> 01:00:05,440
outer solar system as well as in the

1565
01:00:09,510 --> 01:00:07,599
inner solar system so perhaps

1566
01:00:12,150 --> 01:00:09,520
outside the orbit of jupiter as well as

1567
01:00:15,430 --> 01:00:12,160
inside the orbit of jupiter so what

1568
01:00:17,349 --> 01:00:15,440
daman studied showed in this 2021 study

1569
01:00:19,750 --> 01:00:17,359
is when we plot these nucleosynthetic

1570
01:00:22,710 --> 01:00:19,760
anomalies for other elements along with

1571
01:00:25,030 --> 01:00:22,720
nitrogen isotopic compositions

1572
01:00:27,589 --> 01:00:25,040
bulk silicate earth actually plots mac

1573
01:00:29,750 --> 01:00:27,599
in the middle of inner solar system

1574
01:00:31,750 --> 01:00:29,760
flavored iron meteorites and outer solar

1575
01:00:33,910 --> 01:00:31,760
system flavored iron meteorites in all

1576
01:00:36,789 --> 01:00:33,920
of these different isotopic species so

1577
01:00:38,950 --> 01:00:36,799
what this suggests that the inner solar

1578
01:00:41,910 --> 01:00:38,960
system regions where rocky planets like

1579
01:00:43,910 --> 01:00:41,920
our formed already had nitrogen and not

1580
01:00:45,990 --> 01:00:43,920
only that that nitrogen had a distinct

1581
01:00:48,150 --> 01:00:46,000
nitrogen isotropic flavor compared to

1582
01:00:50,309 --> 01:00:48,160
that of the outer solar system regions

1583
01:00:52,549 --> 01:00:50,319
so with that nitrogen isotope mass

1584
01:00:54,309 --> 01:00:52,559
balance what we could show that bulk

1585
01:00:56,710 --> 01:00:54,319
silicate earth's nitrogen isotope

1586
01:00:58,870 --> 01:00:56,720
composition actually required nitrogen

1587
01:01:00,789 --> 01:00:58,880
contribution both from the inner solar

1588
01:01:02,549 --> 01:01:00,799
system region as well as from the outer

1589
01:01:04,230 --> 01:01:02,559
solar system region so that's kind of

1590
01:01:06,069 --> 01:01:04,240
the first take home message

1591
01:01:07,589 --> 01:01:06,079
the second thing we wanted to study is

1592
01:01:09,349 --> 01:01:07,599
whether or not you can establish the

1593
01:01:10,549 --> 01:01:09,359
nitrogen budget of the bulk silicate

1594
01:01:12,870 --> 01:01:10,559
earth through some sort of

1595
01:01:14,870 --> 01:01:12,880
protoplanetary building processes so in

1596
01:01:16,950 --> 01:01:14,880
this we needed to have two kind of

1597
01:01:19,030 --> 01:01:16,960
experimental datasets that i'm not going

1598
01:01:21,030 --> 01:01:19,040
into in detail one is the solubility of

1599
01:01:23,109 --> 01:01:21,040
nitrogen when the planet was largely

1600
01:01:25,109 --> 01:01:23,119
molten meaning how much nitrogen you

1601
01:01:26,950 --> 01:01:25,119
could dissolve from an overlying

1602
01:01:29,349 --> 01:01:26,960
nitrogen bearing atmosphere into the

1603
01:01:31,589 --> 01:01:29,359
silicate magma motion and the other was

1604
01:01:32,950 --> 01:01:31,599
if coral formation was going ongoing

1605
01:01:34,710 --> 01:01:32,960
meaning silicate differentiation and

1606
01:01:36,549 --> 01:01:34,720
metal differentiation was ongoing how

1607
01:01:38,069 --> 01:01:36,559
much nitrogen actually partitioned

1608
01:01:40,069 --> 01:01:38,079
between the metallic core that

1609
01:01:42,470 --> 01:01:40,079
eventually segregated and the silicate

1610
01:01:44,710 --> 01:01:42,480
outer envelope um so the two key things

1611
01:01:46,150 --> 01:01:44,720
to remember in this context is of course

1612
01:01:48,230 --> 01:01:46,160
nitrogen is

1613
01:01:50,470 --> 01:01:48,240
highly atmophile that's why it's we call

1614
01:01:53,109 --> 01:01:50,480
it a volatile element but on top of that

1615
01:01:54,470 --> 01:01:53,119
nitrogen is also cidrophile so at high

1616
01:01:56,390 --> 01:01:54,480
pressure when you don't have a vapor

1617
01:01:57,910 --> 01:01:56,400
phase and when nitrogen is allowed to

1618
01:02:00,230 --> 01:01:57,920
only partition between the molten

1619
01:02:02,950 --> 01:02:00,240
silicate and molten metal nitrogen would

1620
01:02:04,630 --> 01:02:02,960
prefer to go to the molten metal phase

1621
01:02:06,630 --> 01:02:04,640
so with that type of dataset that we

1622
01:02:09,430 --> 01:02:06,640
generated over a range of oxygen partial

1623
01:02:11,190 --> 01:02:09,440
pressure pressure temperature

1624
01:02:12,230 --> 01:02:11,200
melt compositions and everything we

1625
01:02:15,029 --> 01:02:12,240
eventually

1626
01:02:17,029 --> 01:02:15,039
set up to set out to do a mass balance

1627
01:02:19,510 --> 01:02:17,039
calculations within three reservoir

1628
01:02:22,069 --> 01:02:19,520
meaning the proto atmosphere

1629
01:02:24,630 --> 01:02:22,079
the mag motion and the and the metallic

1630
01:02:26,710 --> 01:02:24,640
core and what um so these are the

1631
01:02:28,630 --> 01:02:26,720
equations outlining that meaning

1632
01:02:30,230 --> 01:02:28,640
nitrogen mass in the atmosphere nitrogen

1633
01:02:31,270 --> 01:02:30,240
mass in the magma motion nitrogen mass

1634
01:02:34,309 --> 01:02:31,280
in the core

1635
01:02:36,309 --> 01:02:34,319
equals to the total nitrogen um we can

1636
01:02:38,630 --> 01:02:36,319
calculate the concentration of nitrogen

1637
01:02:40,150 --> 01:02:38,640
by you know dividing the mass of

1638
01:02:41,589 --> 01:02:40,160
nitrogen divided the total mass of a

1639
01:02:43,829 --> 01:02:41,599
given reservoir and then we can

1640
01:02:46,069 --> 01:02:43,839
calculate also the silicate nitrogen

1641
01:02:47,510 --> 01:02:46,079
concentration from the solubility law

1642
01:02:49,670 --> 01:02:47,520
that varies as a function of oxygen

1643
01:02:51,510 --> 01:02:49,680
fugacity and so on so what these plots

1644
01:02:53,190 --> 01:02:51,520
are showing is what would be the

1645
01:02:55,750 --> 01:02:53,200
percentage of nitrogen in the

1646
01:02:58,789 --> 01:02:55,760
proto-atmosphere or in the mag motion or

1647
01:03:00,870 --> 01:02:58,799
in the core as a function of

1648
01:03:03,029 --> 01:03:00,880
oxygen fugacity of protoplanetary

1649
01:03:04,710 --> 01:03:03,039
differentiation for different size

1650
01:03:07,190 --> 01:03:04,720
bodies different carbs are for different

1651
01:03:09,670 --> 01:03:07,200
size bodies so the main thing you should

1652
01:03:11,670 --> 01:03:09,680
pay attention to if you look at most of

1653
01:03:13,270 --> 01:03:11,680
the solar system bodies that underwent

1654
01:03:15,270 --> 01:03:13,280
differentiation including

1655
01:03:17,349 --> 01:03:15,280
rocky planets iron meteorite parent

1656
01:03:19,109 --> 01:03:17,359
bodies uralite parent bodies and so on

1657
01:03:20,789 --> 01:03:19,119
they are thought to be occurring at

1658
01:03:22,630 --> 01:03:20,799
relatively oxidized conditions with

1659
01:03:24,470 --> 01:03:22,640
respect to this iron-oosted buffer that

1660
01:03:25,829 --> 01:03:24,480
is sitting at zero here

1661
01:03:27,510 --> 01:03:25,839
at that type of protoplanetary

1662
01:03:29,349 --> 01:03:27,520
differentiation conditions

1663
01:03:31,029 --> 01:03:29,359
magmotion or the silicate reservoir will

1664
01:03:33,109 --> 01:03:31,039
not be able to retain almost any

1665
01:03:36,390 --> 01:03:33,119
nitrogen because nitrogen will mostly be

1666
01:03:38,069 --> 01:03:36,400
in the atmosphere however um depending

1667
01:03:39,589 --> 01:03:38,079
on the size of the body especially if

1668
01:03:41,029 --> 01:03:39,599
the size of the body that is undergoing

1669
01:03:42,630 --> 01:03:41,039
differentiation is relatively large

1670
01:03:45,349 --> 01:03:42,640
meaning like a mars

1671
01:03:47,109 --> 01:03:45,359
sized embryo type of planetary systems

1672
01:03:49,190 --> 01:03:47,119
you will be able to retain a significant

1673
01:03:51,109 --> 01:03:49,200
fraction of the initial nitrogen budget

1674
01:03:52,710 --> 01:03:51,119
into the metallic core and again this is

1675
01:03:56,390 --> 01:03:52,720
because of that pseudophile element

1676
01:04:00,549 --> 01:03:58,630
in fact this this uh figure kind of

1677
01:04:02,069 --> 01:04:00,559
builds on that so if you calculate the

1678
01:04:05,029 --> 01:04:02,079
percentage of nitrogen in the magma

1679
01:04:06,309 --> 01:04:05,039
motion again this is relatively low if

1680
01:04:07,750 --> 01:04:06,319
the body that is undergoing

1681
01:04:09,990 --> 01:04:07,760
differentiation is relatively small

1682
01:04:11,910 --> 01:04:10,000
meaning the ox nitrogen partial pressure

1683
01:04:13,990 --> 01:04:11,920
in the atmosphere is small you don't you

1684
01:04:15,430 --> 01:04:14,000
don't manage to retain that atmosphere

1685
01:04:17,829 --> 01:04:15,440
nitrogen bearing atmosphere because the

1686
01:04:20,230 --> 01:04:17,839
plant is small however if the planet is

1687
01:04:21,670 --> 01:04:20,240
big meaning if it uh grew really really

1688
01:04:23,109 --> 01:04:21,680
quickly and then underwent

1689
01:04:25,029 --> 01:04:23,119
differentiation you will be able to

1690
01:04:26,549 --> 01:04:25,039
retain some in the magmotion but more

1691
01:04:28,630 --> 01:04:26,559
importantly if

1692
01:04:30,789 --> 01:04:28,640
the planet underwent into instantaneous

1693
01:04:32,789 --> 01:04:30,799
very very rapid accretion then that

1694
01:04:34,230 --> 01:04:32,799
nitrogen cidrophile behavior comes in

1695
01:04:37,190 --> 01:04:34,240
and you'll be able to retain a lot of

1696
01:04:40,069 --> 01:04:37,200
nitrogen in the core of those bodies

1697
01:04:42,630 --> 01:04:40,079
and in fact if you do that way that if

1698
01:04:45,670 --> 01:04:42,640
you build planet like ours earth like

1699
01:04:47,270 --> 01:04:45,680
planet by um

1700
01:04:48,230 --> 01:04:47,280
by uh

1701
01:04:51,270 --> 01:04:48,240
building

1702
01:04:53,430 --> 01:04:51,280
earth by making amalgamating relatively

1703
01:04:55,510 --> 01:04:53,440
large site protoplanetary embryos like

1704
01:04:57,829 --> 01:04:55,520
mars size planets then you can get to

1705
01:04:59,910 --> 01:04:57,839
the present day bulk silicate earth

1706
01:05:01,829 --> 01:04:59,920
nitrogen budget by amalgamating so if

1707
01:05:03,670 --> 01:05:01,839
you are making mars to earth meaning if

1708
01:05:05,750 --> 01:05:03,680
you are accreting a bunch of mars-sized

1709
01:05:07,510 --> 01:05:05,760
planets to eventually make earth you can

1710
01:05:09,109 --> 01:05:07,520
get to the nitrogen abundance of the

1711
01:05:10,870 --> 01:05:09,119
bulk silicate earth you can do the

1712
01:05:13,029 --> 01:05:10,880
similar thing if you make go from the

1713
01:05:15,430 --> 01:05:13,039
moon to the mars and earth-sized bodies

1714
01:05:17,670 --> 01:05:15,440
but if you only make an earth-like

1715
01:05:20,309 --> 01:05:17,680
planet by amalgamating very very small

1716
01:05:22,950 --> 01:05:20,319
planetary protoplant protoplanetary

1717
01:05:24,549 --> 01:05:22,960
systems then the nitrogen budget of that

1718
01:05:26,870 --> 01:05:24,559
bulk silicate earth would have been much

1719
01:05:28,549 --> 01:05:26,880
much lower so accretion of planetary

1720
01:05:31,589 --> 01:05:28,559
embryo size bodies taking place within

1721
01:05:33,109 --> 01:05:31,599
the time scale of aluminum 26 decay that

1722
01:05:34,950 --> 01:05:33,119
gives rise to this nitrogen

1723
01:05:38,150 --> 01:05:34,960
fractionation would be able to supply

1724
01:05:39,910 --> 01:05:38,160
nitrogen budget of our earth

1725
01:05:41,990 --> 01:05:39,920
so in summary rocky planets forming

1726
01:05:43,589 --> 01:05:42,000
region of the solar system had life

1727
01:05:45,430 --> 01:05:43,599
essential volatile elements such as

1728
01:05:47,029 --> 01:05:45,440
nitrogen within one million year of the

1729
01:05:49,029 --> 01:05:47,039
solar system formation

1730
01:05:50,789 --> 01:05:49,039
um the bulk silicate earth source

1731
01:05:52,630 --> 01:05:50,799
nitrogen both from the inner and the

1732
01:05:56,150 --> 01:05:52,640
outer solar system

1733
01:05:58,630 --> 01:05:56,160
regions so not only did it rely on sort

1734
01:06:00,150 --> 01:05:58,640
of delivery of outer solar system

1735
01:06:01,990 --> 01:06:00,160
objects by planetary migrations you

1736
01:06:03,349 --> 01:06:02,000
didn't need that and rapidly grown

1737
01:06:05,990 --> 01:06:03,359
differentiated proto planets could

1738
01:06:07,510 --> 01:06:06,000
supply earth's nitrogen inventory so

1739
01:06:10,069 --> 01:06:07,520
although this session is about this

1740
01:06:12,789 --> 01:06:10,079
geosphere biosphere connection and what

1741
01:06:15,349 --> 01:06:12,799
the message from this talk is that um

1742
01:06:18,309 --> 01:06:15,359
the geosphere could supply this life

1743
01:06:21,270 --> 01:06:18,319
essential nitrogen by acquiring a

1744
01:06:23,109 --> 01:06:21,280
particular planetary building style

1745
01:06:25,430 --> 01:06:23,119
which managed to give nitrogen very very

1746
01:06:27,910 --> 01:06:25,440
early it also has implications for some

1747
01:06:30,230 --> 01:06:27,920
exoplanetary systems what that says is

1748
01:06:31,990 --> 01:06:30,240
you don't need necessarily planetary

1749
01:06:33,750 --> 01:06:32,000
dynamics bringing volatile rich

1750
01:06:35,670 --> 01:06:33,760
materials from the outer solar systems

1751
01:06:37,510 --> 01:06:35,680
of any other exoplanetary systems to

1752
01:06:39,990 --> 01:06:37,520
have life essential volatile elements as

1753
01:06:41,829 --> 01:06:40,000
such as nitrogen uh the inner regions

1754
01:06:43,190 --> 01:06:41,839
that are hot can still have volatile

1755
01:06:45,430 --> 01:06:43,200
elements because some of these volatile

1756
01:06:47,829 --> 01:06:45,440
elements are citrophile so the planets

1757
01:06:50,549 --> 01:06:47,839
as they are growing can hold on to these

1758
01:06:51,990 --> 01:06:50,559
uh life essential volatile elements even

1759
01:06:53,589 --> 01:06:52,000
though they are forming in a hotter

1760
01:06:56,069 --> 01:06:53,599
portion of the disk uh in the inner

1761
01:06:57,109 --> 01:06:56,079
regions of the planet uh close to closer

1762
01:06:59,390 --> 01:06:57,119
to the star

1763
01:07:02,150 --> 01:06:59,400
with that i'll stop thanks

1764
01:07:03,750 --> 01:07:02,160
[Applause]

1765
01:07:05,910 --> 01:07:03,760
thank you so much raj that was an

1766
01:07:09,029 --> 01:07:05,920
awesome talk um so we have a question

1767
01:07:10,390 --> 01:07:09,039
online uh that i will ask um so ben

1768
01:07:11,750 --> 01:07:10,400
johnson says that in a couple of the

1769
01:07:14,390 --> 01:07:11,760
plots showing nitrogen and metal

1770
01:07:16,150 --> 01:07:14,400
isotopes a couple of them had earth

1771
01:07:17,990 --> 01:07:16,160
not right in between the inner and outer

1772
01:07:19,109 --> 01:07:18,000
solar system field could you elaborate

1773
01:07:21,589 --> 01:07:19,119
on that

1774
01:07:23,910 --> 01:07:21,599
um yes so i think the question is about

1775
01:07:25,349 --> 01:07:23,920
these two plots actually they do appear

1776
01:07:28,309 --> 01:07:25,359
right in the middle when you are looking

1777
01:07:30,630 --> 01:07:28,319
at y-axis meaning nitrogen isotope wise

1778
01:07:33,109 --> 01:07:30,640
they are still intermediate what you are

1779
01:07:35,270 --> 01:07:33,119
seeing is on x-axis they are not and

1780
01:07:37,829 --> 01:07:35,280
just because some of these elements like

1781
01:07:39,990 --> 01:07:37,839
molybdenum and ruthenium uh they are

1782
01:07:42,549 --> 01:07:40,000
calcophile and cedarophiles so they got

1783
01:07:45,029 --> 01:07:42,559
added or they fractionated

1784
01:07:47,750 --> 01:07:45,039
at different stages of planet formation

1785
01:07:49,910 --> 01:07:47,760
so if these elements are delivered early

1786
01:07:52,789 --> 01:07:49,920
they will go all the all the way to the

1787
01:07:55,430 --> 01:07:52,799
core on the other hand things like um

1788
01:07:57,349 --> 01:07:55,440
tungsten calcium and other synthetic

1789
01:07:59,750 --> 01:07:57,359
anomalies they are not cedrophile

1790
01:08:02,630 --> 01:07:59,760
enemies so for some of these systems

1791
01:08:04,950 --> 01:08:02,640
on on the x-axis

1792
01:08:06,390 --> 01:08:04,960
bse may not plot exactly in the middle

1793
01:08:08,230 --> 01:08:06,400
but that's not really the point here

1794
01:08:10,230 --> 01:08:08,240
it's really the y-axis spread where the

1795
01:08:11,270 --> 01:08:10,240
nitrogen isotope bc is always smack in

1796
01:08:13,510 --> 01:08:11,280
the middle

1797
01:08:17,349 --> 01:08:13,520
awesome thank you so much for ash and

1798
01:08:21,829 --> 01:08:19,189
and next we have

1799
01:08:24,630 --> 01:08:21,839
uh secret ranjon who is

1800
01:08:26,149 --> 01:08:24,640
currently hailing from

1801
01:08:28,470 --> 01:08:26,159
northwestern although i think we may

1802
01:08:30,789 --> 01:08:28,480
have some congratulations in in the next

1803
01:08:32,950 --> 01:08:30,799
step coming up soon and today he is

1804
01:08:35,990 --> 01:08:32,960
going to uh talk to us about sulfite

1805
01:08:39,510 --> 01:08:36,000
concentrations in in early waters on

1806
01:08:40,709 --> 01:08:39,520
earth so take it away

1807
01:08:42,390 --> 01:08:40,719
thanks very much thanks to the

1808
01:08:44,309 --> 01:08:42,400
organizers for the opportunity to be

1809
01:08:46,470 --> 01:08:44,319
here my name is secret i'm currently a

1810
01:08:48,070 --> 01:08:46,480
post-doctoral fellow at northwestern and

1811
01:08:49,669 --> 01:08:48,080
today i'm excited to tell you about some

1812
01:08:51,590 --> 01:08:49,679
of our work trying to understand the

1813
01:08:52,390 --> 01:08:51,600
nature and speciation of sulfur on early

1814
01:08:53,910 --> 01:08:52,400
earth

1815
01:08:55,990 --> 01:08:53,920
and what that might mean for origins of

1816
01:08:57,590 --> 01:08:56,000
life chemistry

1817
01:08:59,829 --> 01:08:57,600
just to take a step back and kind of

1818
01:09:01,110 --> 01:08:59,839
establish the motivation what i what

1819
01:09:03,910 --> 01:09:01,120
we're really interested in helping

1820
01:09:07,030 --> 01:09:03,920
understand is how a dead planet gave

1821
01:09:08,309 --> 01:09:07,040
rise to a living one specifically we're

1822
01:09:10,470 --> 01:09:08,319
really interested in understanding

1823
01:09:12,070 --> 01:09:10,480
sulfur on on early earth prior to the

1824
01:09:14,070 --> 01:09:12,080
origin of life

1825
01:09:15,829 --> 01:09:14,080
what kinds of sulfur what species of

1826
01:09:17,910 --> 01:09:15,839
sulfur were available

1827
01:09:19,749 --> 01:09:17,920
what environments were they available in

1828
01:09:21,990 --> 01:09:19,759
and what concentrations approximately

1829
01:09:23,430 --> 01:09:22,000
were available

1830
01:09:25,910 --> 01:09:23,440
oh this has an earlier version of my

1831
01:09:28,070 --> 01:09:25,920
talk such as life anyhow for this

1832
01:09:30,070 --> 01:09:28,080
version of my talk i'll say uh

1833
01:09:32,309 --> 01:09:30,080
the key takeaway messages from my talk

1834
01:09:33,829 --> 01:09:32,319
is that sulfite was a prebiotic reagent

1835
01:09:35,910 --> 01:09:33,839
specifically in shallow terrestrial

1836
01:09:37,910 --> 01:09:35,920
waters in early earth and this is

1837
01:09:39,829 --> 01:09:37,920
matters because including sulfide and

1838
01:09:42,149 --> 01:09:39,839
models of prebiotic chemistry enables

1839
01:09:43,990 --> 01:09:42,159
dramatic advances

1840
01:09:46,149 --> 01:09:44,000
the specific idea that we kind of set

1841
01:09:47,990 --> 01:09:46,159
out to explore is the atmosphere as a

1842
01:09:50,070 --> 01:09:48,000
source of sulfur for origins of life

1843
01:09:52,390 --> 01:09:50,080
chemistry specifically to terrestrial

1844
01:09:55,189 --> 01:09:52,400
waters systems like shallow ponds

1845
01:09:56,709 --> 01:09:55,199
the idea is that on early earth as today

1846
01:09:58,070 --> 01:09:56,719
volcanoes would have been the main

1847
01:09:59,750 --> 01:09:58,080
sources of sulfur to the ocean

1848
01:10:01,510 --> 01:09:59,760
atmosphere system

1849
01:10:02,550 --> 01:10:01,520
that's assert to the surface atmosphere

1850
01:10:04,310 --> 01:10:02,560
system

1851
01:10:05,990 --> 01:10:04,320
unlike modern earth there was very

1852
01:10:07,350 --> 01:10:06,000
little oxygen so the lifetime of that

1853
01:10:09,350 --> 01:10:07,360
sulfur should have been significantly

1854
01:10:11,270 --> 01:10:09,360
higher particularly in aqueous solution

1855
01:10:12,790 --> 01:10:11,280
and so we explored the idea that you

1856
01:10:14,390 --> 01:10:12,800
might have been able to establish henry

1857
01:10:16,070 --> 01:10:14,400
equilibrium with the atmosphere

1858
01:10:17,990 --> 01:10:16,080
consequently you dissolve that sulfur it

1859
01:10:20,390 --> 01:10:18,000
speciates and then it gives rise to

1860
01:10:21,669 --> 01:10:20,400
these so-called self-bearing anions and

1861
01:10:23,189 --> 01:10:21,679
the kind of point that we tried to make

1862
01:10:24,709 --> 01:10:23,199
is that if you model if you kind of do

1863
01:10:26,630 --> 01:10:24,719
the simplistic model if you assume the

1864
01:10:28,790 --> 01:10:26,640
atmosphere sets what's going on in

1865
01:10:30,310 --> 01:10:28,800
terrestrial waters you overall find that

1866
01:10:31,910 --> 01:10:30,320
this mechanism can't give you very much

1867
01:10:34,390 --> 01:10:31,920
reduced sulfur species it can't give you

1868
01:10:36,149 --> 01:10:34,400
much very much sulfide but it can give

1869
01:10:38,790 --> 01:10:36,159
you a great deal of sulfite sulfur in

1870
01:10:41,590 --> 01:10:38,800
the plus four oxidation state hso3 minus

1871
01:10:42,709 --> 01:10:41,600
so3 two minus uh specifically we argue

1872
01:10:44,070 --> 01:10:42,719
that you could have had more than

1873
01:10:46,229 --> 01:10:44,080
micromolar concentrations of this

1874
01:10:48,070 --> 01:10:46,239
compound and in the largest

1875
01:10:49,430 --> 01:10:48,080
explosions of volcanic explosions you

1876
01:10:51,189 --> 01:10:49,440
could have approached near millimolar

1877
01:10:53,110 --> 01:10:51,199
concentrations

1878
01:10:54,390 --> 01:10:53,120
why do you care about this we care about

1879
01:10:56,229 --> 01:10:54,400
this because if you try to fold that

1880
01:10:58,149 --> 01:10:56,239
sulfite into experimental studies of

1881
01:10:59,990 --> 01:10:58,159
origins of life chemistry particularly

1882
01:11:01,430 --> 01:11:00,000
towards the rna world it produces

1883
01:11:03,830 --> 01:11:01,440
dramatic advances

1884
01:11:06,229 --> 01:11:03,840
specifically it turns out that sulfite

1885
01:11:08,229 --> 01:11:06,239
enables hcn homologation chemistry that

1886
01:11:09,590 --> 01:11:08,239
has been invoked for uh in a systems

1887
01:11:11,510 --> 01:11:09,600
chemistry approach to synthesis of

1888
01:11:13,510 --> 01:11:11,520
various ribonucleotides

1889
01:11:16,390 --> 01:11:13,520
lipid precursors amino acids and so

1890
01:11:17,270 --> 01:11:16,400
forth sulfite also underlies the only

1891
01:11:18,790 --> 01:11:17,280
known

1892
01:11:21,270 --> 01:11:18,800
pathway for the potentially probiotic

1893
01:11:22,790 --> 01:11:21,280
synthesis of all four ribonucleotides

1894
01:11:25,430 --> 01:11:22,800
and it's also been proposed as a

1895
01:11:26,790 --> 01:11:25,440
solution to a problem that nicole

1896
01:11:29,030 --> 01:11:26,800
identified first the beginning of the

1897
01:11:31,430 --> 01:11:29,040
session how do you access reducing power

1898
01:11:32,950 --> 01:11:31,440
on an on a mostly oxidizing early earth

1899
01:11:34,550 --> 01:11:32,960
maybe you can get that by photolyzing

1900
01:11:36,229 --> 01:11:34,560
that sulfide and giving off a solid

1901
01:11:38,070 --> 01:11:36,239
electron

1902
01:11:39,270 --> 01:11:38,080
so because it seems like sulfite might

1903
01:11:40,709 --> 01:11:39,280
be really productive for prebiotic

1904
01:11:43,270 --> 01:11:40,719
chemistry we really wanted to go back to

1905
01:11:44,630 --> 01:11:43,280
our calculation do it more carefully and

1906
01:11:46,070 --> 01:11:44,640
really ask how much of it could have

1907
01:11:47,990 --> 01:11:46,080
been there and was it where was it

1908
01:11:49,830 --> 01:11:48,000
really available to do this we built a

1909
01:11:52,390 --> 01:11:49,840
kinetic model balancing the sources of

1910
01:11:54,630 --> 01:11:52,400
sulfur in the ultimately from volcanism

1911
01:11:56,709 --> 01:11:54,640
mediated by the atmosphere and the sinks

1912
01:11:58,310 --> 01:11:56,719
of sulfur the things that destroy it we

1913
01:11:59,910 --> 01:11:58,320
particularly focused on this process

1914
01:12:01,830 --> 01:11:59,920
over here disproportionation where

1915
01:12:03,590 --> 01:12:01,840
sulfite molecules get together and

1916
01:12:05,430 --> 01:12:03,600
exchange electrons ultimately making

1917
01:12:07,590 --> 01:12:05,440
more reduced and more oxidized forms of

1918
01:12:10,310 --> 01:12:07,600
sulfur this has been previously proposed

1919
01:12:11,990 --> 01:12:10,320
as the main sink mechanism for uh sulfur

1920
01:12:13,510 --> 01:12:12,000
on anaxic earth

1921
01:12:14,790 --> 01:12:13,520
there's a little problem with modeling

1922
01:12:17,030 --> 01:12:14,800
this unfortunately which is that the

1923
01:12:18,310 --> 01:12:17,040
rate constants for the uh estimates for

1924
01:12:20,950 --> 01:12:18,320
how fast this reaction goes in the

1925
01:12:22,870 --> 01:12:20,960
literature vary by more than a hundred a

1926
01:12:24,709 --> 01:12:22,880
factor of a hundred the literature

1927
01:12:26,149 --> 01:12:24,719
estimate spanned two weeks to greater

1928
01:12:27,669 --> 01:12:26,159
than five years

1929
01:12:29,030 --> 01:12:27,679
and in fact if you check the liter the

1930
01:12:30,630 --> 01:12:29,040
deep literature you find that

1931
01:12:32,630 --> 01:12:30,640
disagreements about this go back uh

1932
01:12:35,270 --> 01:12:32,640
slightly over two centuries

1933
01:12:36,790 --> 01:12:35,280
uh and so we set out to try to do our

1934
01:12:38,709 --> 01:12:36,800
part in trying to resolve this debate to

1935
01:12:40,390 --> 01:12:38,719
some degree and by re i really need to

1936
01:12:42,390 --> 01:12:40,400
give extensive credit to my experimental

1937
01:12:44,550 --> 01:12:42,400
collaborators who are colette abdulazim

1938
01:12:45,830 --> 01:12:44,560
karina kufner and gabriela lozano who

1939
01:12:47,430 --> 01:12:45,840
did most of the actual measurements i'll

1940
01:12:49,030 --> 01:12:47,440
be sharing next

1941
01:12:50,950 --> 01:12:49,040
these are preliminary results so please

1942
01:12:52,310 --> 01:12:50,960
take them with a big grain of salt we're

1943
01:12:54,229 --> 01:12:52,320
we are still doing ex follow-up

1944
01:12:56,790 --> 01:12:54,239
experiments to make sure they're right

1945
01:12:58,070 --> 01:12:56,800
anyhow so what did we do uh our

1946
01:12:59,750 --> 01:12:58,080
experimental objective was to

1947
01:13:01,430 --> 01:12:59,760
differentiate between an anoxic room

1948
01:13:03,510 --> 01:13:01,440
temperature sulfite lifetime of greater

1949
01:13:06,470 --> 01:13:03,520
than a year versus a couple of weeks

1950
01:13:08,470 --> 01:13:06,480
to do this we took solutions of sulfite

1951
01:13:10,709 --> 01:13:08,480
we put them in airtight cuvettes we

1952
01:13:12,550 --> 01:13:10,719
monitored them non-destructively with uv

1953
01:13:14,390 --> 01:13:12,560
spectroscopy and at the end of our

1954
01:13:15,669 --> 01:13:14,400
nine-month experiments we did solution

1955
01:13:17,910 --> 01:13:15,679
analytics to see what had happened to

1956
01:13:19,830 --> 01:13:17,920
that sulfite key experimental constraint

1957
01:13:22,310 --> 01:13:19,840
concerns included o2 exclusion if you

1958
01:13:24,390 --> 01:13:22,320
have o2 it'll kill this it'll really

1959
01:13:26,390 --> 01:13:24,400
robustly oxidize that sulfide very very

1960
01:13:28,229 --> 01:13:26,400
quickly and the long experimental time

1961
01:13:30,470 --> 01:13:28,239
scales

1962
01:13:32,229 --> 01:13:30,480
this summarizes the uv vis monitoring

1963
01:13:34,390 --> 01:13:32,239
results of an initial nine-month pilot

1964
01:13:35,990 --> 01:13:34,400
study we did this is a busy set of plots

1965
01:13:38,630 --> 01:13:36,000
to let me walk you through it

1966
01:13:40,870 --> 01:13:38,640
the top row all represents raw

1967
01:13:42,070 --> 01:13:40,880
raw extinction measured from our uv

1968
01:13:44,070 --> 01:13:42,080
spectrometer

1969
01:13:46,790 --> 01:13:44,080
the bottom row represents the fractional

1970
01:13:48,630 --> 01:13:46,800
change relative to day zero more purple

1971
01:13:50,950 --> 01:13:48,640
cars colors correspond to earlier in the

1972
01:13:52,470 --> 01:13:50,960
experiment more red colors correspond to

1973
01:13:55,030 --> 01:13:52,480
later in the experiment

1974
01:13:57,030 --> 01:13:55,040
the leftmost column gives you the entire

1975
01:13:58,310 --> 01:13:57,040
spectrum that was measured but the short

1976
01:13:59,590 --> 01:13:58,320
wavelengths are useless because they're

1977
01:14:01,270 --> 01:13:59,600
saturated the long wavelengths are

1978
01:14:02,870 --> 01:14:01,280
useless because you have no signal what

1979
01:14:04,630 --> 01:14:02,880
matters is the middle wavelengths which

1980
01:14:05,990 --> 01:14:04,640
are zoomed into the middle column this

1981
01:14:07,990 --> 01:14:06,000
is the linear regime where you have some

1982
01:14:10,149 --> 01:14:08,000
useful information and then the

1983
01:14:11,750 --> 01:14:10,159
rightmost column zooms in specifically

1984
01:14:13,910 --> 01:14:11,760
at 216 nanometers and looks at the

1985
01:14:15,430 --> 01:14:13,920
evolution of that extinction and we see

1986
01:14:17,590 --> 01:14:15,440
that over a time scale of about eight

1987
01:14:19,270 --> 01:14:17,600
and a half months the uh total

1988
01:14:21,669 --> 01:14:19,280
absorption only changed by about 40

1989
01:14:23,430 --> 01:14:21,679
percent indicating a lifetime naively

1990
01:14:24,550 --> 01:14:23,440
indicating a lifetime of sulfite of

1991
01:14:26,070 --> 01:14:24,560
years

1992
01:14:28,310 --> 01:14:26,080
to check this we then did solution

1993
01:14:30,470 --> 01:14:28,320
analytics we found that indeed after

1994
01:14:31,990 --> 01:14:30,480
about nine months only about half of the

1995
01:14:33,350 --> 01:14:32,000
sulphide had been lost

1996
01:14:34,950 --> 01:14:33,360
interestingly it had been converted

1997
01:14:36,470 --> 01:14:34,960
almost entirely into sulfate into

1998
01:14:38,790 --> 01:14:36,480
oxidized sulfur

1999
01:14:41,110 --> 01:14:38,800
uh this is a little bit unexpected

2000
01:14:42,950 --> 01:14:41,120
because and if disproportionation is

2001
01:14:45,110 --> 01:14:42,960
happening we would have expected to find

2002
01:14:47,430 --> 01:14:45,120
reduced forms of sulfur as well such as

2003
01:14:49,590 --> 01:14:47,440
this thiosulfate sulfide elemental

2004
01:14:51,590 --> 01:14:49,600
sulfur but we didn't find any of those

2005
01:14:53,350 --> 01:14:51,600
what we interpret in this tumbin is that

2006
01:14:54,950 --> 01:14:53,360
sulfide disproportionation is even

2007
01:14:57,270 --> 01:14:54,960
slower than implied here what we're

2008
01:14:59,430 --> 01:14:57,280
seeing here is actually direct oxidation

2009
01:15:01,430 --> 01:14:59,440
of the sulfur by o2 leaking in through

2010
01:15:02,870 --> 01:15:01,440
our normally airtight cuvettes and we

2011
01:15:04,630 --> 01:15:02,880
did another couple of quick experiments

2012
01:15:06,310 --> 01:15:04,640
that seemed to confirm this

2013
01:15:08,149 --> 01:15:06,320
since then we've launched a longer term

2014
01:15:10,550 --> 01:15:08,159
series of experiments ultimately started

2015
01:15:13,110 --> 01:15:10,560
last year exploring a range of initial

2016
01:15:15,350 --> 01:15:13,120
sulfide concentrations initial ph and

2017
01:15:17,430 --> 01:15:15,360
background compositions and the results

2018
01:15:18,790 --> 01:15:17,440
of all of them are roughly the same

2019
01:15:19,910 --> 01:15:18,800
this is the same type of plot i showed

2020
01:15:22,390 --> 01:15:19,920
you earlier just for one of our

2021
01:15:23,750 --> 01:15:22,400
experimental runs

2022
01:15:25,350 --> 01:15:23,760
here the

2023
01:15:27,189 --> 01:15:25,360
after about seven and a half months the

2024
01:15:28,950 --> 01:15:27,199
degree of sulfite loss is even less only

2025
01:15:30,149 --> 01:15:28,960
about 10 percent and we think that's

2026
01:15:32,149 --> 01:15:30,159
because we did a much better job

2027
01:15:33,669 --> 01:15:32,159
excluding o2 this time

2028
01:15:35,669 --> 01:15:33,679
so this is consistent with a very long

2029
01:15:37,669 --> 01:15:35,679
sulfite lifetime does this mean that

2030
01:15:39,910 --> 01:15:37,679
sulphite lifetime is going to really

2031
01:15:41,270 --> 01:15:39,920
accumulate to higher high concentrations

2032
01:15:42,709 --> 01:15:41,280
we don't think so because of another

2033
01:15:44,870 --> 01:15:42,719
process that we think is relevant which

2034
01:15:46,630 --> 01:15:44,880
is uv photolysis we know that there was

2035
01:15:48,390 --> 01:15:46,640
a lot of uv on early earth as we've

2036
01:15:50,229 --> 01:15:48,400
heard earlier in this session it turns

2037
01:15:52,070 --> 01:15:50,239
out sulfite really efficiently absorbs

2038
01:15:54,149 --> 01:15:52,080
that uv and it's photolyzed by it

2039
01:15:55,510 --> 01:15:54,159
ultimately going to sulfate and so that

2040
01:15:57,270 --> 01:15:55,520
will provide an upper limit on the

2041
01:16:00,310 --> 01:15:57,280
sulfide concentrations

2042
01:16:01,830 --> 01:16:00,320
uh the preliminary results of our like

2043
01:16:03,189 --> 01:16:01,840
very very preliminary results we haven't

2044
01:16:05,430 --> 01:16:03,199
done anywhere near the sophistication we

2045
01:16:07,510 --> 01:16:05,440
want yet indicates that sulfite remains

2046
01:16:08,550 --> 01:16:07,520
high in some shallow ponds but again

2047
01:16:10,229 --> 01:16:08,560
it's not able to reach high

2048
01:16:12,310 --> 01:16:10,239
concentrations in others specifically in

2049
01:16:14,870 --> 01:16:12,320
ponds with high rates of seepage or in

2050
01:16:16,950 --> 01:16:14,880
deep waters like marine waters

2051
01:16:18,630 --> 01:16:16,960
to summarize the key takeaways i we

2052
01:16:21,590 --> 01:16:18,640
argue that sulfite was a prebiotic

2053
01:16:23,590 --> 01:16:21,600
reagent but in some shallow terrestrial

2054
01:16:25,430 --> 01:16:23,600
waters on early earth with ultimately

2055
01:16:26,870 --> 01:16:25,440
derived from dissolution of volcanogenic

2056
01:16:28,870 --> 01:16:26,880
so2

2057
01:16:30,229 --> 01:16:28,880
and this is based ultimately on

2058
01:16:31,590 --> 01:16:30,239
experiments we've been doing which seem

2059
01:16:34,550 --> 01:16:31,600
to show that room temperature sulfide

2060
01:16:36,470 --> 01:16:34,560
disproportionation is slow

2061
01:16:37,750 --> 01:16:36,480
over overall the sulfide is really

2062
01:16:39,350 --> 01:16:37,760
interesting because it turns out it

2063
01:16:40,630 --> 01:16:39,360
enables really diverse prebiotic

2064
01:16:42,229 --> 01:16:40,640
chemistries particularly towards the

2065
01:16:43,990 --> 01:16:42,239
origin of rna

2066
01:16:46,550 --> 01:16:44,000
and we want to do further laboratory

2067
01:16:48,470 --> 01:16:46,560
measurements to advance both to refine

2068
01:16:50,630 --> 01:16:48,480
kind of the kinetics of this process and

2069
01:16:52,149 --> 01:16:50,640
ideally to look for s4 proxies on the

2070
01:16:54,310 --> 01:16:52,159
rock record i don't know how to do the

2071
01:16:56,470 --> 01:16:54,320
last bit so if any of you do please get

2072
01:16:58,390 --> 01:16:56,480
in touch i'd like to thank my colleagues

2073
01:16:59,830 --> 01:16:58,400
and collaborators and

2074
01:17:01,510 --> 01:16:59,840
funding sources and i'd love to take

2075
01:17:06,470 --> 01:17:01,520
questions thank you

2076
01:17:10,470 --> 01:17:08,229
fantastic thank you for that awesome

2077
01:17:11,350 --> 01:17:10,480
talk do we have a question

2078
01:17:13,590 --> 01:17:11,360
someone

2079
01:17:15,270 --> 01:17:13,600
nope

2080
01:17:17,669 --> 01:17:15,280
all right does anyone have a question if

2081
01:17:19,590 --> 01:17:17,679
not we are a little bit behind so we

2082
01:17:21,110 --> 01:17:19,600
could move on to our next speaker and if

2083
01:17:23,590 --> 01:17:21,120
you have questions for super please find

2084
01:17:30,470 --> 01:17:23,600
them after or or email so thank you so

2085
01:17:36,070 --> 01:17:33,430
up next we have everett shock from asu

2086
01:17:37,990 --> 01:17:36,080
and he is going

2087
01:17:39,189 --> 01:17:38,000
to be let's see if it will come up for

2088
01:17:40,709 --> 01:17:39,199
us

2089
01:17:42,470 --> 01:17:40,719
hi he's going to be talking about um the

2090
01:17:46,470 --> 01:17:42,480
release of energy through organic

2091
01:17:49,350 --> 01:17:48,310
good afternoon it's really a pleasure to

2092
01:17:51,430 --> 01:17:49,360
be here

2093
01:17:53,430 --> 01:17:51,440
first time i've been to a meeting in 27

2094
01:17:54,149 --> 01:17:53,440
months probably like many of the rest of

2095
01:17:56,229 --> 01:17:54,159
you

2096
01:17:58,470 --> 01:17:56,239
it's very exciting times i have an

2097
01:18:00,950 --> 01:17:58,480
optimistic message today

2098
01:18:04,550 --> 01:18:00,960
to go along with that enthusiasm i have

2099
01:18:05,990 --> 01:18:04,560
for being back at a meeting

2100
01:18:08,630 --> 01:18:06,000
this

2101
01:18:10,229 --> 01:18:08,640
work is part of the exploring ocean

2102
01:18:12,790 --> 01:18:10,239
worlds program

2103
01:18:14,390 --> 01:18:12,800
you can also as i will explain later you

2104
01:18:18,070 --> 01:18:14,400
too can do all of these sorts of

2105
01:18:19,350 --> 01:18:18,080
calculations by visiting the worm portal

2106
01:18:22,310 --> 01:18:19,360
so the transform a lot of the

2107
01:18:24,470 --> 01:18:22,320
transformations we're interested in uh

2108
01:18:26,790 --> 01:18:24,480
throughout perhaps many people in this

2109
01:18:29,270 --> 01:18:26,800
audience are various transformations

2110
01:18:32,310 --> 01:18:29,280
from like inorganic to organic simple to

2111
01:18:34,630 --> 01:18:32,320
complex abiotic to biotic transitions

2112
01:18:36,630 --> 01:18:34,640
geochemistry to biochemistry

2113
01:18:38,310 --> 01:18:36,640
the theme of this sort of session and

2114
01:18:41,350 --> 01:18:38,320
what i'm going to try to show you is

2115
01:18:44,950 --> 01:18:41,360
that all of these transitions can be

2116
01:18:47,990 --> 01:18:44,960
accompanied by the release of energy now

2117
01:18:50,950 --> 01:18:48,000
it's not true that i tore this out of

2118
01:18:53,110 --> 01:18:50,960
bob hazen's freshman chemistry notebook

2119
01:18:55,590 --> 01:18:53,120
but this is an idea that's well

2120
01:18:57,750 --> 01:18:55,600
established that if you go from

2121
01:19:00,310 --> 01:18:57,760
reactants to products there's an

2122
01:19:02,790 --> 01:19:00,320
associated energy change if that is a

2123
01:19:05,270 --> 01:19:02,800
spontaneous reaction we talk about the

2124
01:19:07,510 --> 01:19:05,280
gibbs energy change of that reaction the

2125
01:19:10,070 --> 01:19:07,520
higher energy state to lower energy

2126
01:19:12,229 --> 01:19:10,080
state in between we have all the kinetic

2127
01:19:14,310 --> 01:19:12,239
difficulties of how to get from one

2128
01:19:17,430 --> 01:19:14,320
state to the other but the point of this

2129
01:19:19,510 --> 01:19:17,440
is any sort of spontaneous process

2130
01:19:21,350 --> 01:19:19,520
associated with this lowering of the

2131
01:19:23,270 --> 01:19:21,360
gibbs energy and that's what i'm talking

2132
01:19:25,350 --> 01:19:23,280
about today an initial set of

2133
01:19:28,550 --> 01:19:25,360
circumstances or compositions over there

2134
01:19:31,430 --> 01:19:28,560
where it says substrate and then the

2135
01:19:32,870 --> 01:19:31,440
products at a lower energy state and so

2136
01:19:35,750 --> 01:19:32,880
what i'm going to show you is how that's

2137
01:19:38,310 --> 01:19:35,760
possible for that organic synthesis

2138
01:19:39,110 --> 01:19:38,320
happens can happen this way and that

2139
01:19:41,830 --> 01:19:39,120
even

2140
01:19:43,830 --> 01:19:41,840
biological processes can operate in this

2141
01:19:45,990 --> 01:19:43,840
same way

2142
01:19:48,550 --> 01:19:46,000
the point here is that we have many

2143
01:19:50,630 --> 01:19:48,560
cases where the products are more stable

2144
01:19:52,310 --> 01:19:50,640
in a thermodynamic sense than the

2145
01:19:55,110 --> 01:19:52,320
reactants

2146
01:19:57,750 --> 01:19:55,120
so the initial challenge faced by

2147
01:19:59,030 --> 01:19:57,760
practically everything we do is reducing

2148
01:20:00,870 --> 01:19:59,040
co2

2149
01:20:02,709 --> 01:20:00,880
and of course life does this really well

2150
01:20:06,709 --> 01:20:02,719
life continues to do this on a planetary

2151
01:20:07,430 --> 01:20:06,719
scale on earth that's like life's job

2152
01:20:09,510 --> 01:20:07,440
so

2153
01:20:11,990 --> 01:20:09,520
right now of course we are surrounded by

2154
01:20:14,310 --> 01:20:12,000
plenty of photosynthesis where that

2155
01:20:16,629 --> 01:20:14,320
process driven by light involves co2 and

2156
01:20:20,149 --> 01:20:16,639
water to produce organic compounds and

2157
01:20:22,229 --> 01:20:20,159
oxygen but continuously and

2158
01:20:24,709 --> 01:20:22,239
preceding photosynthesis are the

2159
01:20:27,590 --> 01:20:24,719
chemosynthetic reactions where you have

2160
01:20:30,790 --> 01:20:27,600
co2 being reduced to organic compounds

2161
01:20:33,510 --> 01:20:30,800
i'm using hydrogen here to keep track of

2162
01:20:36,310 --> 01:20:33,520
the reductant in reductance involved to

2163
01:20:38,070 --> 01:20:36,320
make organic compounds from co2 and the

2164
01:20:40,470 --> 01:20:38,080
reductants are in the rocks and so this

2165
01:20:43,430 --> 01:20:40,480
is how we're connecting the geosphere to

2166
01:20:48,629 --> 01:20:44,870
what's involved of course is the

2167
01:20:50,390 --> 01:20:48,639
transfer of electrons on the left is a

2168
01:20:52,709 --> 01:20:50,400
plot

2169
01:20:55,669 --> 01:20:52,719
of hydrogen production during late

2170
01:20:58,149 --> 01:20:55,679
stages of serpentinization at

2171
01:21:00,870 --> 01:20:58,159
essentially ambient conditions and it

2172
01:21:02,550 --> 01:21:00,880
depends on what exactly are the minerals

2173
01:21:04,790 --> 01:21:02,560
that are being produced in terms of the

2174
01:21:07,110 --> 01:21:04,800
amount of hydrogen that is produced but

2175
01:21:09,030 --> 01:21:07,120
serpentinization as widely discussed at

2176
01:21:11,830 --> 01:21:09,040
this meeting and elsewhere is a great

2177
01:21:13,510 --> 01:21:11,840
way to liberate hydrogen or

2178
01:21:15,830 --> 01:21:13,520
electrons so of course the electrons

2179
01:21:18,229 --> 01:21:15,840
have the ha that has to be accompanied

2180
01:21:19,990 --> 01:21:18,239
by the ability of the ferrous iron to

2181
01:21:23,590 --> 01:21:20,000
actually in the rocks to actually get

2182
01:21:25,910 --> 01:21:23,600
oxidized to ferric iron um and so these

2183
01:21:28,390 --> 01:21:25,920
processes have to be coupled which all

2184
01:21:30,790 --> 01:21:28,400
comes down to the mineralogy that can

2185
01:21:34,149 --> 01:21:30,800
form during the alteration and this has

2186
01:21:36,310 --> 01:21:34,159
gone into in great detail in the figure

2187
01:21:38,310 --> 01:21:36,320
from the paper on the right showing the

2188
01:21:40,709 --> 01:21:38,320
in different units hydro hydrogen

2189
01:21:42,629 --> 01:21:40,719
productivity uh related to different

2190
01:21:45,750 --> 01:21:42,639
rock types

2191
01:21:48,070 --> 01:21:45,760
and on the right side of the the upper

2192
01:21:49,990 --> 01:21:48,080
left the middle plot there you would

2193
01:21:53,669 --> 01:21:50,000
have ultramafic rocks peridotites and

2194
01:21:56,310 --> 01:21:53,679
going from right to left peridotites uh

2195
01:21:58,149 --> 01:21:56,320
comadites picrites and basalts in terms

2196
01:22:00,310 --> 01:21:58,159
of magnesium number and so you can see

2197
01:22:02,470 --> 01:22:00,320
that the real big hydrogen

2198
01:22:05,350 --> 01:22:02,480
production capability is in the

2199
01:22:07,350 --> 01:22:05,360
ultramafic rocks and what's involved is

2200
01:22:09,590 --> 01:22:07,360
the where the iron ends up which

2201
01:22:11,750 --> 01:22:09,600
minerals are stable and that's in how

2202
01:22:14,310 --> 01:22:11,760
the hydrogen is liberated and this is

2203
01:22:17,669 --> 01:22:14,320
the the release of electrons that are

2204
01:22:19,510 --> 01:22:17,679
essential to the reduction of co2

2205
01:22:21,510 --> 01:22:19,520
there we go we're inventorying that

2206
01:22:23,830 --> 01:22:21,520
again as hydrogen

2207
01:22:26,310 --> 01:22:23,840
so here's a process that biology does

2208
01:22:28,390 --> 01:22:26,320
methanogenesis again there's our

2209
01:22:30,550 --> 01:22:28,400
hydrogen think of that hydrogen as being

2210
01:22:32,390 --> 01:22:30,560
connected to the reactions happening in

2211
01:22:34,470 --> 01:22:32,400
the rock there's the necessity of

2212
01:22:37,110 --> 01:22:34,480
disequilibrium if you're going to make a

2213
01:22:38,870 --> 01:22:37,120
living by being a methanogen you have to

2214
01:22:41,270 --> 01:22:38,880
live in environment where you have co2

2215
01:22:43,510 --> 01:22:41,280
and hydrogen in greater abundance than

2216
01:22:45,110 --> 01:22:43,520
methane so that if you make methane you

2217
01:22:46,470 --> 01:22:45,120
get paid to do it

2218
01:22:48,070 --> 01:22:46,480
we keep track of that with this

2219
01:22:51,030 --> 01:22:48,080
thermodynamic property called the

2220
01:22:53,350 --> 01:22:51,040
affinity there that's at a sub r

2221
01:22:55,590 --> 01:22:53,360
and what it is all it comes down to is a

2222
01:22:57,830 --> 01:22:55,600
comparison of what the equilibrium state

2223
01:22:59,990 --> 01:22:57,840
is versus what are the conditions in a

2224
01:23:01,669 --> 01:23:00,000
natural environment so the equilibrium

2225
01:23:04,709 --> 01:23:01,679
state is involved in that equilibrium

2226
01:23:07,110 --> 01:23:04,719
constant k and the q term is where we

2227
01:23:09,510 --> 01:23:07,120
tie into the natural environment so

2228
01:23:12,390 --> 01:23:09,520
affini when affinities are positive that

2229
01:23:14,709 --> 01:23:12,400
means that energy can be released if the

2230
01:23:16,790 --> 01:23:14,719
reaction is to proceed from left to

2231
01:23:19,110 --> 01:23:16,800
right as written and on the right are a

2232
01:23:23,430 --> 01:23:19,120
couple of examples from a recent paper

2233
01:23:26,149 --> 01:23:23,440
where we show the energy supply for this

2234
01:23:29,510 --> 01:23:26,159
process from mixing of hydrothermal

2235
01:23:31,510 --> 01:23:29,520
fluids released in submarine systems at

2236
01:23:34,070 --> 01:23:31,520
present so based on

2237
01:23:36,390 --> 01:23:34,080
measured data from a basalt hosted

2238
01:23:38,790 --> 01:23:36,400
system there endeavor and an ultramafic

2239
01:23:40,950 --> 01:23:38,800
hosted system rainbow and as those

2240
01:23:43,750 --> 01:23:40,960
fluids mix there's there's greater and

2241
01:23:46,229 --> 01:23:43,760
greater potential for energy to release

2242
01:23:48,470 --> 01:23:46,239
to be released through methanogenesis

2243
01:23:50,470 --> 01:23:48,480
which helps explain why methanogens

2244
01:23:52,870 --> 01:23:50,480
thrive in the vicinity of submarine

2245
01:23:53,910 --> 01:23:52,880
hydrothermal systems

2246
01:23:55,750 --> 01:23:53,920
okay

2247
01:23:57,910 --> 01:23:55,760
let's make this a little bit more

2248
01:24:00,390 --> 01:23:57,920
complex i was saying we can we can go

2249
01:24:03,030 --> 01:24:00,400
from inorganic to organic and from

2250
01:24:05,430 --> 01:24:03,040
simple to complex so let's consider

2251
01:24:07,430 --> 01:24:05,440
something like an amino acid

2252
01:24:09,430 --> 01:24:07,440
synthesis here we're going from co2 to

2253
01:24:11,510 --> 01:24:09,440
ammonia and once again our friend

2254
01:24:12,950 --> 01:24:11,520
hydrogen think again think of that as

2255
01:24:15,350 --> 01:24:12,960
the connection to the reactions

2256
01:24:18,070 --> 01:24:15,360
happening in the rocks producing alanine

2257
01:24:21,189 --> 01:24:18,080
and a whole bunch of water

2258
01:24:24,229 --> 01:24:21,199
again this kind of process involves

2259
01:24:27,030 --> 01:24:24,239
a link to those electrons released by a

2260
01:24:28,149 --> 01:24:27,040
water rock alteration and the question

2261
01:24:30,790 --> 01:24:28,159
is can

2262
01:24:33,030 --> 01:24:30,800
can there be positive affinities

2263
01:24:34,470 --> 01:24:33,040
associated with these kinds of reactions

2264
01:24:36,550 --> 01:24:34,480
now we want to compare a whole bunch of

2265
01:24:38,709 --> 01:24:36,560
these because there's a bunch of amino

2266
01:24:41,189 --> 01:24:38,719
acids we might be interested in one way

2267
01:24:43,350 --> 01:24:41,199
of keeping track of this is to

2268
01:24:45,990 --> 01:24:43,360
account for the average oxidation state

2269
01:24:47,750 --> 01:24:46,000
of carbon in these compounds it's just a

2270
01:24:50,470 --> 01:24:47,760
charge balance thing it's just

2271
01:24:53,189 --> 01:24:50,480
arithmetic to work this out

2272
01:24:56,149 --> 01:24:53,199
but here's how amino acids plot in terms

2273
01:24:58,550 --> 01:24:56,159
of the average oxidation state of carbon

2274
01:25:01,110 --> 01:24:58,560
in amino acids um

2275
01:25:03,590 --> 01:25:01,120
they all of the protein forming amino

2276
01:25:06,310 --> 01:25:03,600
acids span the range of plus one to

2277
01:25:07,830 --> 01:25:06,320
minus one in average oxidation state

2278
01:25:10,310 --> 01:25:07,840
you'll see several that are fairly

2279
01:25:12,470 --> 01:25:10,320
oxidized they're indicated with blue in

2280
01:25:15,110 --> 01:25:12,480
this and the following figures some that

2281
01:25:17,270 --> 01:25:15,120
are right around zero um indicated by

2282
01:25:19,669 --> 01:25:17,280
black in the

2283
01:25:22,070 --> 01:25:19,679
upcoming figures and then the ones where

2284
01:25:27,350 --> 01:25:22,080
the carbon is more reduced

2285
01:25:31,510 --> 01:25:29,510
so here is a plot again for that same

2286
01:25:34,709 --> 01:25:31,520
sort of mixing between a submarine

2287
01:25:37,350 --> 01:25:34,719
hydrothermal fluid and seawater as those

2288
01:25:39,990 --> 01:25:37,360
two fluids mix there is increasing below

2289
01:25:42,950 --> 01:25:40,000
about 200 degrees there is increasingly

2290
01:25:46,390 --> 01:25:42,960
positive affinity for many of the amino

2291
01:25:47,750 --> 01:25:46,400
acid synthesis reactions those overall

2292
01:25:50,550 --> 01:25:47,760
reactions so

2293
01:25:53,110 --> 01:25:50,560
the this is a kind of situation then

2294
01:25:54,629 --> 01:25:53,120
where the organic synthesis you might be

2295
01:25:58,629 --> 01:25:54,639
interested in

2296
01:26:01,110 --> 01:25:58,639
there is energy release associated

2297
01:26:03,430 --> 01:26:01,120
with that organic synthesis process that

2298
01:26:06,070 --> 01:26:03,440
means the organic compounds are more

2299
01:26:08,709 --> 01:26:06,080
stable than the inorganic mixture of

2300
01:26:11,990 --> 01:26:08,719
stuff that happens spontaneously as hot

2301
01:26:14,470 --> 01:26:12,000
water pours into cold seawater now there

2302
01:26:16,470 --> 01:26:14,480
are many other kinds of processes on the

2303
01:26:18,629 --> 01:26:16,480
earth where various

2304
01:26:21,830 --> 01:26:18,639
disequilibrium can be generated i'm

2305
01:26:23,750 --> 01:26:21,840
using this hydrothermal mixing example

2306
01:26:25,910 --> 01:26:23,760
today because it's one i'm particularly

2307
01:26:29,189 --> 01:26:25,920
familiar with

2308
01:26:30,310 --> 01:26:29,199
but i want to make this point that even

2309
01:26:32,790 --> 01:26:30,320
on our

2310
01:26:35,110 --> 01:26:32,800
heavily oxidant polluted world because

2311
01:26:38,149 --> 01:26:35,120
of all that photosynthesis going on out

2312
01:26:40,310 --> 01:26:38,159
there this process remains in these

2313
01:26:43,030 --> 01:26:40,320
kinds of environments at the bottom of

2314
01:26:45,669 --> 01:26:43,040
our ocean right now an energy releasing

2315
01:26:48,550 --> 01:26:45,679
process let's ask a methanogen here's

2316
01:26:50,950 --> 01:26:48,560
some baby pictures of mathana kaldakakis

2317
01:26:53,430 --> 01:26:50,960
yanashii one of the

2318
01:26:55,110 --> 01:26:53,440
types of methanogens living around

2319
01:26:57,350 --> 01:26:55,120
submarine hydrothermal systems it's an

2320
01:27:00,070 --> 01:26:57,360
autotrophic methanogen it uses co2 and

2321
01:27:02,470 --> 01:27:00,080
hydrogen to make methane it also uses

2322
01:27:04,070 --> 01:27:02,480
co2 and hydrogen to make all of its

2323
01:27:05,669 --> 01:27:04,080
organic compounds all of its

2324
01:27:08,229 --> 01:27:05,679
biomolecules

2325
01:27:11,590 --> 01:27:08,239
so we take the genome

2326
01:27:13,990 --> 01:27:11,600
of methane haldicoccus enagi convert it

2327
01:27:17,189 --> 01:27:14,000
over into all the protein sequences and

2328
01:27:18,550 --> 01:27:17,199
when we do so we get 1787

2329
01:27:20,629 --> 01:27:18,560
proteins

2330
01:27:23,430 --> 01:27:20,639
and here's just one example

2331
01:27:26,629 --> 01:27:23,440
of an overall reaction to produce this

2332
01:27:28,709 --> 01:27:26,639
protein this is what this organism does

2333
01:27:32,390 --> 01:27:28,719
it takes in co2

2334
01:27:35,590 --> 01:27:32,400
ammonia sulfur and a whole boatload of

2335
01:27:37,590 --> 01:27:35,600
hydrogen again remember that hydrogen is

2336
01:27:40,470 --> 01:27:37,600
our link to the rocks it's the water

2337
01:27:42,550 --> 01:27:40,480
rock reaction that is really that's

2338
01:27:44,390 --> 01:27:42,560
written where the iron is being oxidized

2339
01:27:46,149 --> 01:27:44,400
the water is being reduced to hydrogen

2340
01:27:48,149 --> 01:27:46,159
and you get a rather astonishing

2341
01:27:49,590 --> 01:27:48,159
stoichiometric reaction coefficient on

2342
01:27:51,430 --> 01:27:49,600
that hydrogen and there's the

2343
01:27:53,350 --> 01:27:51,440
composition of the protein we don't

2344
01:27:56,629 --> 01:27:53,360
usually think of protein synthesis this

2345
01:27:58,790 --> 01:27:56,639
way but if we were to ask our buddy mj

2346
01:28:00,709 --> 01:27:58,800
about it

2347
01:28:01,430 --> 01:28:00,719
mj would say yeah that's what i have to

2348
01:28:03,590 --> 01:28:01,440
do

2349
01:28:04,790 --> 01:28:03,600
i start with co2 i've got to make this

2350
01:28:06,709 --> 01:28:04,800
protein

2351
01:28:09,350 --> 01:28:06,719
well let's consider the affinities of

2352
01:28:10,310 --> 01:28:09,360
these reactions to make these proteins

2353
01:28:15,669 --> 01:28:10,320
um

2354
01:28:18,070 --> 01:28:15,679
states with the conditions that are

2355
01:28:21,189 --> 01:28:18,080
available in the environment

2356
01:28:24,390 --> 01:28:21,199
these are the resulting affinities for

2357
01:28:26,870 --> 01:28:24,400
producing all 1787

2358
01:28:28,950 --> 01:28:26,880
of those proteins in that same mixing

2359
01:28:30,550 --> 01:28:28,960
environment where the hydrothermal

2360
01:28:33,030 --> 01:28:30,560
fluids from the rainbow of enfield on

2361
01:28:36,629 --> 01:28:33,040
the mid-atlantic ridge mix with seawater

2362
01:28:37,910 --> 01:28:36,639
on the left the data are presented in uh

2363
01:28:40,709 --> 01:28:37,920
affinities

2364
01:28:43,350 --> 01:28:40,719
per mole of protein notice that the unit

2365
01:28:45,189 --> 01:28:43,360
the units here are mega joules so that's

2366
01:28:47,189 --> 01:28:45,199
some serious energy

2367
01:28:48,229 --> 01:28:47,199
they're presented in the on the right

2368
01:28:49,669 --> 01:28:48,239
side

2369
01:28:52,790 --> 01:28:49,679
in terms of

2370
01:28:54,870 --> 01:28:52,800
affinities per mole of amino acid in the

2371
01:28:58,470 --> 01:28:54,880
proteins and you'll notice this familiar

2372
01:29:00,709 --> 01:28:58,480
now structure of the blue black and red

2373
01:29:04,070 --> 01:29:00,719
colors where the more reduced the

2374
01:29:06,149 --> 01:29:04,080
protein is the more energy is released

2375
01:29:08,470 --> 01:29:06,159
by its synthesis but the point i want to

2376
01:29:10,950 --> 01:29:08,480
make hopefully is not

2377
01:29:14,149 --> 01:29:10,960
escaping here is that

2378
01:29:15,990 --> 01:29:14,159
all the proteins in this methanogen are

2379
01:29:19,189 --> 01:29:16,000
more stable

2380
01:29:21,270 --> 01:29:19,199
than the inorganic starting material

2381
01:29:23,750 --> 01:29:21,280
that in the surrounding environment

2382
01:29:24,550 --> 01:29:23,760
where it lives

2383
01:29:26,470 --> 01:29:24,560
so

2384
01:29:27,590 --> 01:29:26,480
if you're thinking about

2385
01:29:29,750 --> 01:29:27,600
ways to

2386
01:29:32,470 --> 01:29:29,760
to do organic synthesis you're thinking

2387
01:29:34,709 --> 01:29:32,480
about ways to build complexity to go

2388
01:29:36,870 --> 01:29:34,719
from inorganic to organic to go from

2389
01:29:40,310 --> 01:29:36,880
abiotic to biotic and geochemistry to

2390
01:29:43,750 --> 01:29:40,320
biochemistry don't fight thermodynamics

2391
01:29:46,070 --> 01:29:43,760
you can find lots of ways in which you

2392
01:29:48,629 --> 01:29:46,080
can get thermodynamics on your side you

2393
01:29:51,750 --> 01:29:48,639
can have energy release

2394
01:29:54,070 --> 01:29:51,760
associated with all of those processes

2395
01:29:57,189 --> 01:29:54,080
you can then reduce your problem to

2396
01:29:59,030 --> 01:29:57,199
mechanisms and kinetics only he says ha

2397
01:30:00,950 --> 01:29:59,040
but anyway the point is get

2398
01:30:03,110 --> 01:30:00,960
thermodynamics on your side if you want

2399
01:30:06,310 --> 01:30:03,120
to know learn how to do all of these

2400
01:30:08,629 --> 01:30:06,320
calculations visit the worm portal

2401
01:30:10,950 --> 01:30:08,639
there's the link to it where all of

2402
01:30:13,590 --> 01:30:10,960
these calculations are made available to

2403
01:30:15,669 --> 01:30:13,600
you it's free it's all in jupiter

2404
01:30:17,450 --> 01:30:15,679
notebooks let's go

2405
01:30:22,310 --> 01:30:17,460
all right thank you

2406
01:30:25,510 --> 01:30:24,229
thank you so much everyone um i think

2407
01:30:27,350 --> 01:30:25,520
all right well nathan has a question

2408
01:30:29,510 --> 01:30:27,360
right here

2409
01:30:31,189 --> 01:30:29,520
all right that's a fascinating talk

2410
01:30:34,629 --> 01:30:31,199
so my question to you is do you think

2411
01:30:36,070 --> 01:30:34,639
there are abiotic amino acids being

2412
01:30:37,990 --> 01:30:36,080
formed today

2413
01:30:40,070 --> 01:30:38,000
in hydrothermal vents and the sites that

2414
01:30:41,669 --> 01:30:40,080
you are describing and

2415
01:30:43,510 --> 01:30:41,679
the extension to that question is do you

2416
01:30:47,030 --> 01:30:43,520
think there are abiotic

2417
01:30:49,430 --> 01:30:47,040
proteins that are being formed in these

2418
01:30:53,430 --> 01:30:49,440
locations today

2419
01:30:54,709 --> 01:30:53,440
i have no idea i know that there are

2420
01:30:57,189 --> 01:30:54,719
abiotic

2421
01:30:58,149 --> 01:30:57,199
amino acids that have formed

2422
01:31:01,030 --> 01:30:58,159
on

2423
01:31:04,390 --> 01:31:01,040
meteor in the meteorite record a lot of

2424
01:31:06,310 --> 01:31:04,400
that makes a considerable sense

2425
01:31:08,229 --> 01:31:06,320
when you link it to the aqueous

2426
01:31:10,950 --> 01:31:08,239
alteration events that occurred on

2427
01:31:13,590 --> 01:31:10,960
meteorite parent bodies it's also an

2428
01:31:16,070 --> 01:31:13,600
energy releasing process in the similar

2429
01:31:17,990 --> 01:31:16,080
way i have a feeling that if there were

2430
01:31:21,110 --> 01:31:18,000
a bio that

2431
01:31:23,990 --> 01:31:21,120
i i kind of doubt that there's that it

2432
01:31:26,390 --> 01:31:24,000
would be easy to um measure

2433
01:31:27,430 --> 01:31:26,400
abiotic amino acids

2434
01:31:29,189 --> 01:31:27,440
in a

2435
01:31:33,750 --> 01:31:29,199
setting on the earth

2436
01:31:34,709 --> 01:31:33,760
because life operates faster than

2437
01:31:41,510 --> 01:31:34,719
the

2438
01:31:42,629 --> 01:31:41,520
that burst into flame are not good to

2439
01:31:43,910 --> 01:31:42,639
eat

2440
01:31:46,229 --> 01:31:43,920
and so you

2441
01:31:49,189 --> 01:31:46,239
biology has to beat the abiotic

2442
01:31:51,510 --> 01:31:49,199
reactions um and and that's usually what

2443
01:31:53,510 --> 01:31:51,520
it does so i suspect that it would be

2444
01:31:55,510 --> 01:31:53,520
hard to find because biology would be

2445
01:31:59,110 --> 01:31:55,520
there uh pounding on it and in terms of

2446
01:32:01,750 --> 01:31:59,120
proteins i i don't imagine that there

2447
01:32:03,830 --> 01:32:01,760
would be an a full abiotic synthesis of

2448
01:32:05,910 --> 01:32:03,840
a protein but there is a thermodynamic

2449
01:32:08,470 --> 01:32:05,920
drive to for energy to be released if

2450
01:32:10,310 --> 01:32:08,480
that were to occur

2451
01:32:11,750 --> 01:32:10,320
thank you and i think we can do one more

2452
01:32:13,510 --> 01:32:11,760
question and then we'll move on to the

2453
01:32:16,149 --> 01:32:13,520
next speaker

2454
01:32:17,430 --> 01:32:16,159
well okay let me say also we um i want

2455
01:32:18,629 --> 01:32:17,440
to move on to the next speaker just

2456
01:32:20,070 --> 01:32:18,639
because i think we'll probably get cut

2457
01:32:22,149 --> 01:32:20,080
off online but we are not going to be

2458
01:32:23,669 --> 01:32:22,159
kicked out of this room so um everett if

2459
01:32:25,030 --> 01:32:23,679
you don't mind sticking around and

2460
01:32:26,310 --> 01:32:25,040
anyone else who is a speaker and if you

2461
01:32:28,149 --> 01:32:26,320
have questions for any of our speakers

2462
01:32:30,470 --> 01:32:28,159
oh you can we can still do one more but

2463
01:32:31,750 --> 01:32:30,480
um but after that you know that we can

2464
01:32:33,510 --> 01:32:31,760
all stick around and keep asking

2465
01:32:35,669 --> 01:32:33,520
questions within the room i just don't

2466
01:32:37,030 --> 01:32:35,679
want the us to get cut off online so go

2467
01:32:38,950 --> 01:32:37,040
ahead with your questions i'll start by

2468
01:32:40,790 --> 01:32:38,960
saying i enjoyed your talk and i suspect

2469
01:32:42,950 --> 01:32:40,800
that this might be better hashtag over

2470
01:32:44,709 --> 01:32:42,960
drinks but i'll say for this room that

2471
01:32:46,470 --> 01:32:44,719
the ribosome will disagree with you

2472
01:32:50,390 --> 01:32:46,480
because it takes three equivalents of

2473
01:32:52,390 --> 01:32:50,400
ntp to put an amino acid into a protein

2474
01:32:54,149 --> 01:32:52,400
that's a kinetic problem no it's not a

2475
01:32:56,149 --> 01:32:54,159
kinetic problem it has to do with the

2476
01:32:57,990 --> 01:32:56,159
fact that it takes energy to be accurate

2477
01:33:00,149 --> 01:32:58,000
it takes energy to do kinetic proof

2478
01:33:03,270 --> 01:33:00,159
reading and takes energy to activate a

2479
01:33:05,110 --> 01:33:03,280
carboxylic acid into a phospholipid form

2480
01:33:07,270 --> 01:33:05,120
to get into the amine

2481
01:33:09,910 --> 01:33:07,280
well those all sounded like kinetic

2482
01:33:12,629 --> 01:33:09,920
problems to me and mechanistic problems

2483
01:33:15,270 --> 01:33:12,639
and not thermodynamic problems

2484
01:33:16,709 --> 01:33:15,280
this does sound like a beer conversation

2485
01:33:18,310 --> 01:33:16,719
all right so up next we're going to

2486
01:33:20,870 --> 01:33:18,320
learn about uh formation rates of

2487
01:33:22,950 --> 01:33:20,880
ferrocyanide in the early earth and that

2488
01:33:24,390 --> 01:33:22,960
is going to be with zoe todd who's

2489
01:33:27,590 --> 01:33:24,400
joining us from

2490
01:33:29,430 --> 01:33:27,600
the university of washington

2491
01:33:36,070 --> 01:33:29,440
and

2492
01:33:39,110 --> 01:33:37,750
all right hi everyone thanks for

2493
01:33:41,189 --> 01:33:39,120
sticking around we'll try not to take

2494
01:33:42,070 --> 01:33:41,199
too much of the poster time uh so today

2495
01:33:43,830 --> 01:33:42,080
i'm going to be telling you about

2496
01:33:45,590 --> 01:33:43,840
formation rates of ferrocyanide on the

2497
01:33:47,189 --> 01:33:45,600
early earth and implications for

2498
01:33:48,870 --> 01:33:47,199
prebiotic chemistry

2499
01:33:51,110 --> 01:33:48,880
so in case you haven't heard it at this

2500
01:33:52,709 --> 01:33:51,120
conference so far hydrogen cyanide is

2501
01:33:54,470 --> 01:33:52,719
commonly implicated in prebiotic

2502
01:33:56,310 --> 01:33:54,480
chemistry it's gotten lots of shout outs

2503
01:33:57,910 --> 01:33:56,320
in various sessions so i'm either going

2504
01:33:59,669 --> 01:33:57,920
to reiterate that or if you haven't

2505
01:34:03,270 --> 01:33:59,679
heard it before state it for the first

2506
01:34:06,070 --> 01:34:03,280
time so this historically dates back to

2507
01:34:08,070 --> 01:34:06,080
oro synthesis back in the 1960s where he

2508
01:34:11,270 --> 01:34:08,080
first determined that you can synthesize

2509
01:34:13,030 --> 01:34:11,280
adenine so the letter a in dna and rna

2510
01:34:16,229 --> 01:34:13,040
the a and atp it's all throughout

2511
01:34:18,310 --> 01:34:16,239
biology from pantomimerizing hcn so take

2512
01:34:19,510 --> 01:34:18,320
five hcns put them together you get

2513
01:34:21,510 --> 01:34:19,520
adeny

2514
01:34:23,430 --> 01:34:21,520
so that's back in history cyanide is

2515
01:34:25,910 --> 01:34:23,440
important what about more recent

2516
01:34:27,750 --> 01:34:25,920
prebiotic chemistry well cyanide is

2517
01:34:31,350 --> 01:34:27,760
still very important

2518
01:34:33,270 --> 01:34:31,360
so i'm going to show a variety of very

2519
01:34:35,350 --> 01:34:33,280
detailed chemical schemes here you're

2520
01:34:36,790 --> 01:34:35,360
not supposed to understand every detail

2521
01:34:38,629 --> 01:34:36,800
of all of them that's not the purpose

2522
01:34:41,350 --> 01:34:38,639
for having them here mainly i just want

2523
01:34:43,830 --> 01:34:41,360
to point out that hey in steve benner's

2524
01:34:45,590 --> 01:34:43,840
2020 paper describing one version of

2525
01:34:47,830 --> 01:34:45,600
prebiotic chemistry

2526
01:34:49,750 --> 01:34:47,840
hcn is used as a feedstock molecule and

2527
01:34:52,390 --> 01:34:49,760
has a source of synthesis to make

2528
01:34:53,910 --> 01:34:52,400
biomolecules and precursors of life

2529
01:34:55,510 --> 01:34:53,920
hdn is not specific just to this

2530
01:34:57,189 --> 01:34:55,520
chemistry you can also look at the

2531
01:34:59,590 --> 01:34:57,199
cyanosulfidic chemistry coming out of

2532
01:35:01,430 --> 01:34:59,600
john sutherland's lab and again hydrogen

2533
01:35:03,990 --> 01:35:01,440
cyanide is the basis for this network

2534
01:35:06,229 --> 01:35:04,000
that can make amino acids lipids sugars

2535
01:35:07,750 --> 01:35:06,239
and ribonucleotides finally i'll just

2536
01:35:10,470 --> 01:35:07,760
throw up one more and again this is

2537
01:35:12,790 --> 01:35:10,480
becker at all 2016. hydrogen cyanide is

2538
01:35:14,390 --> 01:35:12,800
a source molecule different type of

2539
01:35:16,629 --> 01:35:14,400
synthesis to get to the same

2540
01:35:19,030 --> 01:35:16,639
biomolecules and precursors of life

2541
01:35:21,189 --> 01:35:19,040
so by now hopefully i have reiterated or

2542
01:35:22,629 --> 01:35:21,199
reinstated the fact that hcn is commonly

2543
01:35:24,629 --> 01:35:22,639
implicated in various probiotic

2544
01:35:26,629 --> 01:35:24,639
chemistry and hcn makes the building

2545
01:35:29,270 --> 01:35:26,639
blocks of life

2546
01:35:31,189 --> 01:35:29,280
so that's awesome but does hcn actually

2547
01:35:33,189 --> 01:35:31,199
exist on the early earth and we can ask

2548
01:35:35,910 --> 01:35:33,199
that question and fortunately the answer

2549
01:35:37,990 --> 01:35:35,920
is probably there are sources of hcn on

2550
01:35:39,750 --> 01:35:38,000
the early earth so these range from

2551
01:35:41,590 --> 01:35:39,760
things like lightning generation in the

2552
01:35:43,830 --> 01:35:41,600
atmosphere so you can think the

2553
01:35:45,990 --> 01:35:43,840
classical miller uri spark discharge

2554
01:35:47,750 --> 01:35:46,000
experiment this done in a fairly

2555
01:35:50,070 --> 01:35:47,760
reducing atmosphere can give you quite

2556
01:35:52,229 --> 01:35:50,080
efficient amounts of hydrogen cyanide

2557
01:35:54,229 --> 01:35:52,239
similarly uv photochemistry interacting

2558
01:35:56,149 --> 01:35:54,239
in the atmosphere can also synthesize

2559
01:35:58,149 --> 01:35:56,159
hydrogen cyanide and both of those two

2560
01:36:00,149 --> 01:35:58,159
processes are much more efficient in

2561
01:36:01,669 --> 01:36:00,159
more reducing atmospheres drop-off

2562
01:36:03,510 --> 01:36:01,679
inefficiency when you go to a more

2563
01:36:05,430 --> 01:36:03,520
oxidizing atmosphere if you want an

2564
01:36:06,870 --> 01:36:05,440
atmosphere composition independent

2565
01:36:09,270 --> 01:36:06,880
source of hydrogen cyanide you could

2566
01:36:12,229 --> 01:36:09,280
look to impact delivery or perhaps also

2567
01:36:14,470 --> 01:36:12,239
impact synthesis of hydrogen cyanide so

2568
01:36:16,950 --> 01:36:14,480
hcn is important and hcn could have been

2569
01:36:19,510 --> 01:36:16,960
there through a variety of means

2570
01:36:21,109 --> 01:36:19,520
but there's one catch you knew it was

2571
01:36:23,270 --> 01:36:21,119
coming right it sounded too good to be

2572
01:36:25,270 --> 01:36:23,280
true and that is that hydrogen cyanide

2573
01:36:27,510 --> 01:36:25,280
can degrade over time so you can begin

2574
01:36:29,430 --> 01:36:27,520
to see a premise of a potential issue

2575
01:36:31,830 --> 01:36:29,440
for prebiotic chemistry either you have

2576
01:36:33,830 --> 01:36:31,840
to be continuously synthesizing hcn it

2577
01:36:35,350 --> 01:36:33,840
has to be continuously available or the

2578
01:36:38,790 --> 01:36:35,360
prebiotic chemistry that makes use of

2579
01:36:40,709 --> 01:36:38,800
hcn has to happen on such a faster scale

2580
01:36:43,030 --> 01:36:40,719
than the degradation occurs

2581
01:36:45,270 --> 01:36:43,040
or you need some other geochemical

2582
01:36:47,109 --> 01:36:45,280
source to kind of save you from this

2583
01:36:49,350 --> 01:36:47,119
potential issue

2584
01:36:50,870 --> 01:36:49,360
so one potential suggestion here and i

2585
01:36:52,709 --> 01:36:50,880
should state we do not know at this

2586
01:36:54,310 --> 01:36:52,719
point how fast necessarily that

2587
01:36:56,229 --> 01:36:54,320
chemistry works under a planetary

2588
01:36:57,750 --> 01:36:56,239
environment so these are open questions

2589
01:36:58,870 --> 01:36:57,760
that we're not entirely sure about at

2590
01:37:00,550 --> 01:36:58,880
this time

2591
01:37:02,629 --> 01:37:00,560
so one potential solution is that you

2592
01:37:04,790 --> 01:37:02,639
could store hydrogen cyanide in the form

2593
01:37:07,189 --> 01:37:04,800
of ferrocyanide so if you have a ferrous

2594
01:37:09,270 --> 01:37:07,199
iron center fe2 plus you have six

2595
01:37:12,550 --> 01:37:09,280
cyanide ligands bound to it this becomes

2596
01:37:14,070 --> 01:37:12,560
a much more stable form of cyanide you

2597
01:37:16,070 --> 01:37:14,080
can potentially store this in stock

2598
01:37:17,430 --> 01:37:16,080
pilot for later use so this is

2599
01:37:19,590 --> 01:37:17,440
demonstrated in this really nice figure

2600
01:37:21,510 --> 01:37:19,600
from sasilov at all 2020 where if you

2601
01:37:23,350 --> 01:37:21,520
have h standing the atmosphere you can

2602
01:37:26,310 --> 01:37:23,360
potentially concentrate that in surface

2603
01:37:27,910 --> 01:37:26,320
waters with things like fe2 plus and we

2604
01:37:29,990 --> 01:37:27,920
heard a lot about sulfur and you can see

2605
01:37:31,910 --> 01:37:30,000
sulfide appears in these lakes as well

2606
01:37:33,830 --> 01:37:31,920
then if you evaporate and ultimately

2607
01:37:35,590 --> 01:37:33,840
precipitate out some of these salts this

2608
01:37:37,990 --> 01:37:35,600
is a good way to potentially accumulate

2609
01:37:41,270 --> 01:37:38,000
decent amounts of ferrocyanide and be

2610
01:37:44,470 --> 01:37:41,280
able to use cyanide later on

2611
01:37:46,790 --> 01:37:44,480
and this again goes back to 1995 keith

2612
01:37:48,870 --> 01:37:46,800
and miller with a paper titled was

2613
01:37:50,390 --> 01:37:48,880
ferrocyanide a prebiotic reagent but

2614
01:37:52,390 --> 01:37:50,400
they investigate this primarily from a

2615
01:37:54,390 --> 01:37:52,400
thermodynamic perspective and also with

2616
01:37:56,629 --> 01:37:54,400
a focus on the oceans

2617
01:37:58,550 --> 01:37:56,639
so what i wanted to know was how fast

2618
01:38:00,470 --> 01:37:58,560
does this chemistry work you know if

2619
01:38:02,310 --> 01:38:00,480
we're thinking about kinetics is this an

2620
01:38:03,750 --> 01:38:02,320
issue or is this not an issue at all or

2621
01:38:06,070 --> 01:38:03,760
what can the environment constrain about

2622
01:38:07,910 --> 01:38:06,080
the chemistry so we ask the question how

2623
01:38:09,910 --> 01:38:07,920
fast and efficiently does ferrocyanide

2624
01:38:11,910 --> 01:38:09,920
form under a range of plausible

2625
01:38:13,669 --> 01:38:11,920
planetary conditions so we tested the

2626
01:38:15,669 --> 01:38:13,679
rate of formation and the yield as a

2627
01:38:17,270 --> 01:38:15,679
function of concentration of reactants

2628
01:38:19,669 --> 01:38:17,280
and ph

2629
01:38:22,390 --> 01:38:19,679
so to show you some sets of experimental

2630
01:38:24,709 --> 01:38:22,400
data this is showing 0.1 millimolar of

2631
01:38:27,669 --> 01:38:24,719
fe2 plus and varying concentrations of

2632
01:38:29,830 --> 01:38:27,679
cyanide at a ph of 9. so what you can

2633
01:38:33,270 --> 01:38:29,840
see is that this reaction occurs quite

2634
01:38:36,070 --> 01:38:33,280
fast so if you you see a very steep

2635
01:38:37,669 --> 01:38:36,080
increase initially in your concentration

2636
01:38:39,590 --> 01:38:37,679
of ferrocyanide which is determined

2637
01:38:41,189 --> 01:38:39,600
through uv vis absorption measurements

2638
01:38:43,030 --> 01:38:41,199
you can see we only have to monitor this

2639
01:38:44,950 --> 01:38:43,040
reaction for about four minutes for it

2640
01:38:46,470 --> 01:38:44,960
to be pretty much done

2641
01:38:48,470 --> 01:38:46,480
so we can determine the rate constant

2642
01:38:50,790 --> 01:38:48,480
from that first 10 seconds and the final

2643
01:38:52,229 --> 01:38:50,800
concentration of ferrocyanide under a

2644
01:38:53,990 --> 01:38:52,239
range of conditions

2645
01:38:55,990 --> 01:38:54,000
so here the left-hand panel is showing

2646
01:38:57,510 --> 01:38:56,000
you k that rate constant of initial

2647
01:38:59,510 --> 01:38:57,520
formation and the right-hand panel is

2648
01:39:01,350 --> 01:38:59,520
showing you the final concentration as a

2649
01:39:03,270 --> 01:39:01,360
function of concentration of cyanide and

2650
01:39:04,950 --> 01:39:03,280
across a range of phs

2651
01:39:07,590 --> 01:39:04,960
so a couple things stick out here and

2652
01:39:09,350 --> 01:39:07,600
this is primarily in the ph dependence

2653
01:39:11,830 --> 01:39:09,360
so this reaction is fastest and most

2654
01:39:13,910 --> 01:39:11,840
efficient at ph 8 to 9 and it's

2655
01:39:16,310 --> 01:39:13,920
interesting that it drops off at

2656
01:39:18,310 --> 01:39:16,320
more acidic phs but also what really

2657
01:39:20,470 --> 01:39:18,320
caught my eye is that ph 10 is not

2658
01:39:23,750 --> 01:39:20,480
better than ph 9 you do not see this

2659
01:39:25,830 --> 01:39:23,760
linear increase when you change the ph

2660
01:39:27,910 --> 01:39:25,840
so this is with varying cyanide

2661
01:39:29,910 --> 01:39:27,920
concentrations we can do the same set of

2662
01:39:32,229 --> 01:39:29,920
experiments holding cyanide constant and

2663
01:39:35,669 --> 01:39:32,239
then varying the concentration of fe2

2664
01:39:37,270 --> 01:39:35,679
plus again investigate the same ph range

2665
01:39:39,430 --> 01:39:37,280
make similar plots and again we find

2666
01:39:41,270 --> 01:39:39,440
that ph 89 are going to generally be the

2667
01:39:43,350 --> 01:39:41,280
fastest and the most efficient and we

2668
01:39:45,109 --> 01:39:43,360
observe the similar behavior

2669
01:39:46,950 --> 01:39:45,119
so what does this mean for ferrocyanide

2670
01:39:49,910 --> 01:39:46,960
in the planetary context

2671
01:39:51,590 --> 01:39:49,920
so on a planet you can have pretty much

2672
01:39:54,149 --> 01:39:51,600
you know free choice or constrain

2673
01:39:55,189 --> 01:39:54,159
choices of concentrations ph and

2674
01:39:57,189 --> 01:39:55,199
temperature depending on what

2675
01:39:59,030 --> 01:39:57,199
environment you're considering and just

2676
01:40:00,390 --> 01:39:59,040
as a reminder hydrogen cyanide we like

2677
01:40:02,790 --> 01:40:00,400
it because it can synthesize

2678
01:40:04,709 --> 01:40:02,800
biomolecules so we can start to imagine

2679
01:40:06,310 --> 01:40:04,719
a little model of a lake on the surface

2680
01:40:07,669 --> 01:40:06,320
of early earth we have some partial

2681
01:40:09,910 --> 01:40:07,679
pressure hydrogen cyanide in the

2682
01:40:11,990 --> 01:40:09,920
atmosphere can equilibrate with surface

2683
01:40:13,910 --> 01:40:12,000
waters through henry log equilibrium

2684
01:40:15,510 --> 01:40:13,920
that we heard about earlier

2685
01:40:17,750 --> 01:40:15,520
and then if you have a stream coming in

2686
01:40:19,510 --> 01:40:17,760
that contains some amount of fe2 plus

2687
01:40:22,149 --> 01:40:19,520
which you would likely have on the early

2688
01:40:24,550 --> 01:40:22,159
earth before the oxygenation event then

2689
01:40:25,910 --> 01:40:24,560
you can form ferrocyanide and we can ask

2690
01:40:27,270 --> 01:40:25,920
the question all right given our

2691
01:40:29,270 --> 01:40:27,280
experimentally determined rates and

2692
01:40:30,950 --> 01:40:29,280
yields how much ferrocyanide can you

2693
01:40:33,430 --> 01:40:30,960
possibly accumulate

2694
01:40:35,350 --> 01:40:33,440
so this is a preliminary calculation and

2695
01:40:37,109 --> 01:40:35,360
i would caution you that the numbers are

2696
01:40:38,950 --> 01:40:37,119
very dependent on what assumptions you

2697
01:40:41,189 --> 01:40:38,960
make so what is the flow rate into the

2698
01:40:43,030 --> 01:40:41,199
lake what is the volume of the lake what

2699
01:40:45,270 --> 01:40:43,040
is the concentration of free ferrous

2700
01:40:46,950 --> 01:40:45,280
iron that you're assuming but what i do

2701
01:40:49,030 --> 01:40:46,960
have a lot more confidence in is the

2702
01:40:51,750 --> 01:40:49,040
change between different phs and the

2703
01:40:53,990 --> 01:40:51,760
trends with ph and concentration of

2704
01:40:56,070 --> 01:40:54,000
ferrous iron so what i'll draw your

2705
01:40:57,669 --> 01:40:56,080
attention to here is that you really do

2706
01:40:59,350 --> 01:40:57,679
not get a lot of ferrocyanide

2707
01:41:01,109 --> 01:40:59,360
accumulation i'm showing you the amount

2708
01:41:03,189 --> 01:41:01,119
of time here to reach one millimolar of

2709
01:41:04,790 --> 01:41:03,199
ferrocyanide which is kind of like a

2710
01:41:06,229 --> 01:41:04,800
thumbs up concentration for getting

2711
01:41:07,430 --> 01:41:06,239
prebiotic chemistry to work in the

2712
01:41:09,830 --> 01:41:07,440
laboratory

2713
01:41:11,669 --> 01:41:09,840
so at ph 6 and low fe2 plus

2714
01:41:14,070 --> 01:41:11,679
concentrations this can take a really

2715
01:41:16,390 --> 01:41:14,080
long time talking millions of years

2716
01:41:18,629 --> 01:41:16,400
but if you go to more basic phs and bump

2717
01:41:20,470 --> 01:41:18,639
up the ferrous iron concentration you

2718
01:41:22,310 --> 01:41:20,480
can have this occurring plausibly than

2719
01:41:23,430 --> 01:41:22,320
tens of thousands of years or a thousand

2720
01:41:26,870 --> 01:41:23,440
years or even if you're really

2721
01:41:29,030 --> 01:41:26,880
optimistic 100 years 10 years

2722
01:41:30,390 --> 01:41:29,040
so overall conclusions we measured these

2723
01:41:32,470 --> 01:41:30,400
rates of formation and yields of

2724
01:41:34,149 --> 01:41:32,480
ferrocyanide over a range of planetarily

2725
01:41:35,910 --> 01:41:34,159
relevant parameters including

2726
01:41:37,830 --> 01:41:35,920
concentration of ph temperature

2727
01:41:39,510 --> 01:41:37,840
experiments are in progress so we will

2728
01:41:40,390 --> 01:41:39,520
be able to add that parameter in here as

2729
01:41:42,070 --> 01:41:40,400
well

2730
01:41:43,750 --> 01:41:42,080
and we find that the accumulation of

2731
01:41:46,229 --> 01:41:43,760
ferrocyanide is favored at slightly

2732
01:41:49,109 --> 01:41:46,239
alkaline phs and under these favorable

2733
01:41:51,109 --> 01:41:49,119
conditions and with assumptions that are

2734
01:41:53,270 --> 01:41:51,119
hopefully reasonable but again subject

2735
01:41:55,990 --> 01:41:53,280
to your range of constraints for the

2736
01:41:57,750 --> 01:41:56,000
early earth ferrocyanide stock piling to

2737
01:41:59,669 --> 01:41:57,760
significant concentrations may be able

2738
01:42:02,149 --> 01:41:59,679
to occur on reasonable time scales for

2739
01:42:04,229 --> 01:42:02,159
probiotic chemistry and with that i will

2740
01:42:05,430 --> 01:42:04,239
thank david catling and nick woken for

2741
01:42:07,910 --> 01:42:05,440
helping collaborations on this

2742
01:42:10,229 --> 01:42:07,920
experiment this project funding sources

2743
01:42:16,790 --> 01:42:10,239
and of course peter my pony he says

2744
01:42:21,350 --> 01:42:18,629
we'll have to bring peter with you next

2745
01:42:23,990 --> 01:42:21,360
time um all right do we have a question

2746
01:42:25,669 --> 01:42:24,000
for zoe

2747
01:42:27,350 --> 01:42:25,679
yeah it looks like we have a couple and

2748
01:42:28,629 --> 01:42:27,360
and we can ask as many and if you have

2749
01:42:29,910 --> 01:42:28,639
questions for other people feel free to

2750
01:42:32,470 --> 01:42:29,920
go ahead and start lining up i know we

2751
01:42:34,950 --> 01:42:32,480
had one for everett and so yeah go ahead

2752
01:42:39,430 --> 01:42:34,960
um how he seems to get out the hype

2753
01:42:41,350 --> 01:42:39,440
today how do you cyanide from the paris

2754
01:42:45,189 --> 01:42:41,360
sorry say that again yes

2755
01:42:47,030 --> 01:42:45,199
who is to recover the hcn from

2756
01:42:48,629 --> 01:42:47,040
yeah that's a great question so it has

2757
01:42:49,910 --> 01:42:48,639
been suggested that you can do thermal

2758
01:42:51,750 --> 01:42:49,920
processing

2759
01:42:53,510 --> 01:42:51,760
so you might need somewhat high

2760
01:42:54,629 --> 01:42:53,520
temperatures to this there are various

2761
01:42:55,750 --> 01:42:54,639
references that have been said in

2762
01:42:58,310 --> 01:42:55,760
literature but i would love to see

2763
01:43:00,870 --> 01:42:58,320
someone do that study um much more

2764
01:43:02,550 --> 01:43:00,880
thoroughly and revisit that question

2765
01:43:04,390 --> 01:43:02,560
there's another possibility is that uv

2766
01:43:06,709 --> 01:43:04,400
irradiation of ferrocyanide can do a

2767
01:43:08,709 --> 01:43:06,719
reaction called photoequation where you

2768
01:43:10,950 --> 01:43:08,719
can kick off one cyanide and put a water

2769
01:43:12,870 --> 01:43:10,960
molecule on and then it might rapidly

2770
01:43:14,470 --> 01:43:12,880
lose more cyanide so it might be

2771
01:43:16,310 --> 01:43:14,480
possible to get some amount of cyanide

2772
01:43:18,149 --> 01:43:16,320
from that mechanism as well

2773
01:43:20,470 --> 01:43:18,159
thanks for the question

2774
01:43:23,990 --> 01:43:20,480
awesome and we can come right over here

2775
01:43:25,669 --> 01:43:24,000
uh paul remember university of cambridge

2776
01:43:27,189 --> 01:43:25,679
really nice talk um

2777
01:43:29,750 --> 01:43:27,199
it looked to me from your plot although

2778
01:43:31,430 --> 01:43:29,760
is it difficult to tell from um from the

2779
01:43:33,270 --> 01:43:31,440
way that the gradients are shown that it

2780
01:43:34,870 --> 01:43:33,280
seems that the concentration of iron

2781
01:43:36,550 --> 01:43:34,880
matters a lot more

2782
01:43:38,390 --> 01:43:36,560
than the ph it looks like if you just

2783
01:43:40,950 --> 01:43:38,400
have a lot of iron it works pretty

2784
01:43:43,030 --> 01:43:40,960
quickly regardless of the ph would that

2785
01:43:45,270 --> 01:43:43,040
be an accurate interpretation or does ph

2786
01:43:47,270 --> 01:43:45,280
matter more than the way that i'm kind

2787
01:43:48,870 --> 01:43:47,280
of looking at them no i agree with you

2788
01:43:50,629 --> 01:43:48,880
there and i think the other thing too is

2789
01:43:52,470 --> 01:43:50,639
i'm showing you six orders of magnitude

2790
01:43:54,629 --> 01:43:52,480
of ferrocyanide or ferrous iron

2791
01:43:57,350 --> 01:43:54,639
concentration so that's really a wide

2792
01:43:59,189 --> 01:43:57,360
range of parameter space there and your

2793
01:44:00,629 --> 01:43:59,199
ferrous iron concentration is somewhat

2794
01:44:02,629 --> 01:44:00,639
degenerate with the volume of the lake

2795
01:44:04,709 --> 01:44:02,639
you're assuming in your flow rate in my

2796
01:44:06,629 --> 01:44:04,719
proline preliminary model here so

2797
01:44:08,390 --> 01:44:06,639
depending on those assumptions

2798
01:44:10,550 --> 01:44:08,400
i think the role of ph should not be

2799
01:44:13,270 --> 01:44:10,560
understated but again the dominating

2800
01:44:14,629 --> 01:44:13,280
factor is going to be those assumptions

2801
01:44:16,149 --> 01:44:14,639
thanks paul

2802
01:44:17,350 --> 01:44:16,159
awesome thank you and then i think we

2803
01:44:20,149 --> 01:44:17,360
have a question right here i think

2804
01:44:21,990 --> 01:44:20,159
everett this might have been for you go

2805
01:44:24,390 --> 01:44:22,000
ahead and you can ask a question

2806
01:44:25,750 --> 01:44:24,400
hi jessica bowman from georgia tech um

2807
01:44:27,270 --> 01:44:25,760
maybe i missed it in the beginning but i

2808
01:44:28,950 --> 01:44:27,280
was wondering if you could comment on

2809
01:44:31,669 --> 01:44:28,960
your assumptions about presence of

2810
01:44:37,109 --> 01:44:31,679
oxygen in these uh reactions and also on

2811
01:44:41,109 --> 01:44:39,189
yes this is for me not everett is that

2812
01:44:43,189 --> 01:44:41,119
true okay yes yes so we did these all

2813
01:44:45,830 --> 01:44:43,199
exclusively in an anaerobic environment

2814
01:44:49,590 --> 01:44:45,840
so in a glove box oxygen free oxygen

2815
01:44:51,750 --> 01:44:49,600
reduced degas water zero ppm oxygen

2816
01:44:52,550 --> 01:44:51,760
inside the glove box if you don't do

2817
01:44:53,990 --> 01:44:52,560
that

2818
01:44:55,669 --> 01:44:54,000
this reaction is

2819
01:44:57,669 --> 01:44:55,679
you know you can't study it properly

2820
01:44:59,430 --> 01:44:57,679
because the ferrous iron oxidizes very

2821
01:45:01,030 --> 01:44:59,440
quickly in an oxygen environment so

2822
01:45:02,310 --> 01:45:01,040
you've got to be careful about that and

2823
01:45:04,629 --> 01:45:02,320
you know the early earth we're assuming

2824
01:45:06,550 --> 01:45:04,639
it's pretty auction free so yeah

2825
01:45:09,480 --> 01:45:06,560
thank you for the question awesome and

2826
01:45:12,790 --> 01:45:09,490
let's let's thank zoe thank you so much

2827
01:45:15,910 --> 01:45:14,470
thank you and i think that we had some

2828
01:45:17,430 --> 01:45:15,920
questions online and if there was anyone

2829
01:45:18,870 --> 01:45:17,440
else in the room you guys can feel free

2830
01:45:20,310 --> 01:45:18,880
to stand up and i'm just going to ask

2831
01:45:22,709 --> 01:45:20,320
the questions and if the speakers are

2832
01:45:24,149 --> 01:45:22,719
still here great if not um raj are you

2833
01:45:27,270 --> 01:45:24,159
still here i think this one is for you

2834
01:45:29,669 --> 01:45:27,280
so um and in i'm not exactly sure who

2835
01:45:31,830 --> 01:45:29,679
that is but someone in in uh says can

2836
01:45:34,070 --> 01:45:31,840
you comment on the observed difference

2837
01:45:36,470 --> 01:45:34,080
of uh nitrogen between the inner and

2838
01:45:39,270 --> 01:45:36,480
outer solar system materials and what's

2839
01:45:41,990 --> 01:45:39,280
the main loss mechanism for n from a

2840
01:45:45,270 --> 01:45:42,000
rocky protoplanet

2841
01:45:52,709 --> 01:45:45,280
nitrogen yeah yeah yeah i can give you

2842
01:45:58,709 --> 01:45:55,990
um yeah so isotopically i guess

2843
01:46:00,870 --> 01:45:58,719
the outer solar system materials are

2844
01:46:03,910 --> 01:46:00,880
heavier in delta 15

2845
01:46:06,550 --> 01:46:03,920
higher values uh inner solar system uh

2846
01:46:08,790 --> 01:46:06,560
lower delta 59 values

2847
01:46:10,709 --> 01:46:08,800
uh so we do need certain amount of outer

2848
01:46:12,470 --> 01:46:10,719
solar system or cc type of material as

2849
01:46:14,950 --> 01:46:12,480
far as nitrogen isotopic compositions

2850
01:46:17,590 --> 01:46:14,960
will as far as the loss mechanism the

2851
01:46:19,669 --> 01:46:17,600
majority of the loss from quantitative

2852
01:46:22,390 --> 01:46:19,679
building blocks as they are forming

2853
01:46:25,030 --> 01:46:22,400
protoplanets would be through formation

2854
01:46:26,870 --> 01:46:25,040
of atmosphere that eventually gets lost

2855
01:46:29,030 --> 01:46:26,880
because these protoplanets are

2856
01:46:30,950 --> 01:46:29,040
so small they cannot hold on to their

2857
01:46:32,950 --> 01:46:30,960
onto their atmosphere because

2858
01:46:35,109 --> 01:46:32,960
there is not enough gravitational pull

2859
01:46:37,030 --> 01:46:35,119
so that's so that differentiation and

2860
01:46:39,430 --> 01:46:37,040
atmosphere formation and atmospheric

2861
01:46:41,109 --> 01:46:39,440
glow out would be the dominant mechanism

2862
01:46:43,189 --> 01:46:41,119
of losing nitrogen

2863
01:46:45,510 --> 01:46:43,199
uh at the same time you do need to

2864
01:46:46,629 --> 01:46:45,520
retain certain amount to make nitrogen

2865
01:46:48,550 --> 01:46:46,639
budget

2866
01:46:49,350 --> 01:46:48,560
explained in our planet and that's why

2867
01:46:51,830 --> 01:46:49,360
we

2868
01:46:52,550 --> 01:46:51,840
explain like relatively faster growth of

2869
01:46:54,550 --> 01:46:52,560
some

2870
01:46:56,229 --> 01:46:54,560
protoplanets so that nitrogen can be

2871
01:46:58,070 --> 01:46:56,239
filled onto the body

2872
01:47:00,310 --> 01:46:58,080
and partitioned into the pore and

2873
01:47:02,229 --> 01:47:00,320
retained in the atmosphere but the major

2874
01:47:04,870 --> 01:47:02,239
loss mechanism is through protoplanetary

2875
01:47:06,709 --> 01:47:04,880
atmospheric blowout

2876
01:47:08,149 --> 01:47:06,719
awesome thank you

2877
01:47:09,750 --> 01:47:08,159
and i think we hit all the questions

2878
01:47:11,270 --> 01:47:09,760
online so thank you everyone who stuck

2879
01:47:12,870 --> 01:47:11,280
through to the end and thank you again

2880
01:47:15,270 --> 01:47:12,880
to all of our speakers this was an

2881
01:47:16,950 --> 01:47:15,280
awesome very dynamic session so thank