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[Music]

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today I'm going to be talking about a

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possible new level planetary bio

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signature my you see the in situ

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isotopic and elemental analysis of

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pyrite so first I want to start out by

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talking just a little bit about Mars so

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Mars is our neighboring planet and in

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many ways is the most similar to us from

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past missions we have gotten a lot of

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evidence about how Mars was habitable in

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the past so about three to four billion

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years ago we have evidence that Mars

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could have been habitable we have

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evidence of large bodies of waters just

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flowing on Mars and it's very curious

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because at the same time period the

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earth was experiencing very similar

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conditions and we also know that during

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three to four billion years ago that's

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when light started to emerge here on

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earth so if we know that that's why one

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of the biggest questions right now is

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was there ever life on Mars that life

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ever emerged on Mars and so that's why

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the upcoming missions are seeking signs

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of past life we have for example the

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Mars 2020 Rover in the ExoMars 2020

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Rovers which main mission is to speak

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signs of past life I am very excited

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about the Mars 2020 Rover this mission

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particularly because with this mission

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we can have the upcoming mission of

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sample return and I'm very optimistic

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about that one even though we still

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don't have a launch date for that one

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but I'm optimistic that it will happen

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it will be also more get Martian samples

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here and we're gonna be able to study

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them analyze them run them through every

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single study we can and try to find out

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if there was ever life on Mars and

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besides that there are proposed future

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missions for human exploration and NASA

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ESA

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china-russia they all have put forward

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proposals for human exploration and even

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though right now it's a little bit

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controversial whether we want humans

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walking on mars given the fact that so

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many space agencies are to put forward

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humans I'm also optimistic that it will

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happen in the near future because I'm

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bringing this up because there are so

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many missions that want to find signs of

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life but what if what would be a very

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convincing evidence of life that's

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something we need to think a lot about

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and so that brings me to talk about bio

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signatures so bio signatures are

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features whose presence or abundance can

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be attributed to life this diagram right

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here was actually produced by the Mars

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2020 team when they were writing their

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proposals and they did a lot of thinking

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about what are the bio signatures that

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we want to look at when we go through

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Mars what are the bio signatures that

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will tell us something whether life was

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there or not so for example they have

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organics

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so organic molecules that are

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representative of life macro structure

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so think of fossils stromatolites are a

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great example of this chemistry so

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chemical abundance of like an element a

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molecule something that is produced by

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biological processes minerals minerals

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that are formed through direct or

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indirect processes of life micro

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structures are micro fossils so think

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about biofilms for example and isotopes

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so isotope fractionation is mainly on

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stable isotopes that are produced by

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biological processes so these are all

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good candidates for good bio signatures

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however they all have their advantages

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and disadvantages organics for example

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the problem with them is that they

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cannot be preserved for many of many

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millions of years they were thinking of

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Mars for example where we expect life to

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if it was ever there it was probably

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there 3 billion years ago or a little

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more and so it's difficult to think that

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the organics have survived there even

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with a high radiation that Mars receives

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macro structures and micro structures

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have the same problem that they're very

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acceptable to false interpretation this

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is something that nASA has suffered a

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lot from something that people should

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try not to just see a rock and

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automatically assume that it's the

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stromatolite or microbial matter and so

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forth chemistry just by looking at the

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chemistry it doesn't really tell you

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much you need to couple it with other

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types of measurements isotopes is the

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same problem minerals minerals can be

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robust because they can be preserved for

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longer times they can be preserved for

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millions and maybe billions of years

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however the problem with them is that

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most of the minerals that are formed by

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biological processes they can also be

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formed by abiotic processes and so

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they're on ambiguous in that they're

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ambiguous sorry and that creates a

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problem um however I'm an inorganic

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geochemist and I love minerals and so

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that's why I think of a lot about

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minerals that can serve as a bio

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signature and my absolute favorite

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mineral is pyrite and so that's why my

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big question is can Pirates serve as a

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bio signature so here I just want to

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explain what is pyrite specifically what

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is sedimentary pyrite say I have a

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figure here of sediments we see this

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shiny thing that looks like gold but

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it's not don't be fooled by it

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this this is pyrite this picture here is

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kind of an odd picture usually in

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sediments we get from boiled high rates

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so these are like agglomeration so if

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microcrystalline pyre is in there

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spherical

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I couldn't find a high-resolution one so

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I just put this shiny one which I also

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like anyhow so sedimentary pies there

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sulphide minerals and the way that they

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form in the waters and in sediments is

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by the help of microbial sulfate

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reduction so these microbes they take

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the sulfate and they take the organic

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matter and they metabolize it and then

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they were just two hydrogen sulfide

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which eventually can become into pyrite

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and because of this because pyrite is

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iron sulfide sulfide is reducing species

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it is stable under anoxic conditions and

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so this has a lot of implications about

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reducing potentials in marine sediments

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that's why one of the reasons why pirate

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is used a lot for paleo environmental

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proxies a really cool thing about pyrite

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is that when pirate is flora mean it can

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incorporate trace elements that are in

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its surroundings so it just incorporates

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it into its chemical structure and it

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can lock them in and so when we're

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looking at pyrite we can look at the

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trace elements and get a good idea about

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the environmental condition when that

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pirate was for me

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likewise is an iron sulfide minerals so

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there's a lot of important implications

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about the biogeochemical so first cycle

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a lot of people like to study the sulfur

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isotopes because it's very robust you

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look at the so for fractionation between

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the sulfate the source and the pyrite

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and you can get some estimate about the

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biological effect and so then again so

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my question can pirates serve as a bio

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signature so here I have again the

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diagram that I just showed you this so

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we're just gonna go over what we just

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learned about pyrite to see if it really

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works as a bio signature so we know the

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sedimentary pyrite forms through

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microbial sulfate reduction so it is a

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mineral that forms through biological

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processes so then that checks out the

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mineral box so 34s and Powerade shows

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depletion from source and this is in

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part due to biology so the sulfur

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isotopes can be Valley

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well surfer if biology helped in

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producing pyrite so that checks the

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isotope box and as we just learned trace

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elements they get incorporated into the

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pyrite and they can track the

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biogeochemical conditions and so it

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checks out the chemistry box so out of

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all of the five boxes it checks three of

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them so that is very encouraging however

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this doesn't really tell us if it works

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as a bio signature it just tells us that

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we should work hard and try to find out

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if it does however a fair warning other

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pyro formation types exist so para

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doesn't only form in sediments it forms

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in hydrothermal deposits it formed

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through igneous processes and forms

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through magmatic policies metamorphism

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and so forth many people like to tell me

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like you can just get the pirate and

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know if it's igneous or if it's the

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matter worth it and so forth that is not

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true there's there's from boydle pirate

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it's thought to be only sedimentary and

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no it forms to hydrothermal metamorphic

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and igneous processes as well um and so

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we need to be very very careful because

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we if we go to another planetary body

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and we find pyrite that's not really

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telling us anything so we need to look

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more into its chemistry and so I did a

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pilot study where I got a lot of pirate

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rings from a lot of different places on

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earth this figure here shows the

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different places where we collected this

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pirate grains and we measured the trace

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element concentrations and the sulfur

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isotopes and so I created this

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classifier that could differentiate

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pirate formation types my question was

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like could we differentiate them using a

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classifier and so currently we can just

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define what is biological and what is

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abiotic Oh

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abiotic in pirate so I try to classify

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them in turn

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formation types so try to classify them

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between sedimentary hydrothermal and

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metamorphic oh wait it's a big image

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okay so data acquisition how do I get my

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data so if we're sulfur isotopes I use

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Simms secondary ion mass spectrometer

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this is me working in Washington

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University in st. Louis and David Fikes

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lab this is the Simpson strim --nt and

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so this is all done in situ so I get the

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grains and I decide which targets I want

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to measure and so this has a laser it

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just snaps through it so this is a

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representation of what we do this is an

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80s image of a hydro thermal pressure

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rock sample the mustard color here is

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pyrite and maybe we can just look at

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this zooms in image here these black

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spots are the the spot selections where

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we sat through it and got these sulfur

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isotopes data so we always do a transect

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we do a transit because we want to see

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the evolution of the pyrite growing for

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example from here we can tell that the

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Pirates started growing here and then it

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started spreading out and so we wanted

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to track that evolution and get the

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silver eyes it's a data from it for

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trace elements in pyrite we use a very

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similar method this one is called laser

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ablation inductively coupled plasma mass

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spectrometer it works in the very

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similar fashion is also in situ it uses

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a laser as well you select the target

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spots you always want to use the same

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target spot you stop through it and then

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you get multiple trace elements

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measurements the good thing about the

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instrument that we use is that it has an

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automated

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element mapping so as you can see from

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this image here we can get the we can

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get a map of where these trace elements

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are in our sample and that's very

280
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helpful for trying to interpret how

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these trace elements get incorporated so

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as I mentioned I am using a statistical

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classification I use random forests

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which is a supervised machine learning

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algorithm unfortunately I don't really

286
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have time to explain how I do this

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classification but if anyone's

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interested in learning just let me know

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I know a really easy software that you

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don't need any data science background

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so it's really good so what we did we

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did we collect about 400 stains our

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variables we use 11 features so we use

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10 trees elements of them by essential

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elements and we use Delta 34 s as the

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isotope our classification I trained the

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classifier to distinguish between

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information types so sedimentary

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hydrothermal metamorphic this is an

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example of one of the experiments that I

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made this is only one decision tree out

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00:14:16,740 --> 00:14:13,600
of the 500 that I usually do and it just

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shows how it how the tree branches

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itself as it starts as it starts

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classifying them into their distinguish

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formation type so these are the results

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00:14:36,090 --> 00:14:32,350
from a pilot study so I here I'm showing

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three different experiments the first

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one was only looking at trace elements

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without looking at sulfur isotopes

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second one was only looking at sulfur

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isotopes without trace elements and the

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third one looking at trace elements and

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sulfur isotopes together what we're in

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here are a confusion matrices and yeah

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we're pretty confusing and so we're not

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going to go over them now but what I

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want you guys to notice is the accuracy

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of them so what we can see is that when

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we coupled both trace elements and

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sulfur isotopes together

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is when we get the highest accuracy so

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that's very encouraging however for the

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sulfur isotopes the Icarus II was fairly

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low and things of course makes sense if

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you go back to Becky's talk when she was

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talking about like geologic time scale

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and all the different the different

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chemistry that existed throughout time

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it does make sense that sulfur isotopes

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will vary like thing I forgot to mention

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but my pirate grades third throughout

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geologic time so I have from the our

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00:15:43,090 --> 00:15:40,699
camp Proterra soy vanilla throughout all

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of geologic time so of course they will

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bury however traits elements they did a

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very good job and we were surprised this

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we really didn't understand why he was

339
00:15:56,350 --> 00:15:53,470
doing such a great job so moving forward

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00:15:59,019 --> 00:15:56,360
these are all Asian samples we wanted to

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really understand how it is that trace

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elements in sulfur isotopes how they get

343
00:16:06,519 --> 00:16:03,410
incorporated into pirate and not only

344
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that but how diagenesis affect that

345
00:16:14,850 --> 00:16:11,329
original signature and so that is what

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we're doing now we I am collecting

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00:16:20,199 --> 00:16:17,930
samples from all of these sites the ones

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00:16:22,449 --> 00:16:20,209
in greens are sites that I've already

349
00:16:25,530 --> 00:16:22,459
collected samples from the ones in red

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are the ones that I still have to go to

351
00:16:31,379 --> 00:16:28,519
Black Sea is the classic extended site

352
00:16:35,110 --> 00:16:31,389
there's a lot of studies on this area

353
00:16:39,189 --> 00:16:35,120
Santa Monica Basin in California it's a

354
00:16:41,410 --> 00:16:39,199
seasonally variable water column and so

355
00:16:44,340 --> 00:16:41,420
there's a lot of pollen there's an

356
00:16:47,680 --> 00:16:44,350
oxygen minimum zone is a very dynamic

357
00:16:50,920 --> 00:16:47,690
continental margin I did a lot of work

358
00:16:53,100 --> 00:16:50,930
here trying to get pyrite and it turns

359
00:16:55,629 --> 00:16:53,110
out that there's this very amazing

360
00:16:58,240 --> 00:16:55,639
cryptic sylph recycling happening there

361
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that's a sulfate gets reduced to sulfide

362
00:17:02,860 --> 00:17:01,160
and immediately gets oxidized back so he

363
00:17:06,220 --> 00:17:02,870
didn't really get any hiring out of it

364
00:17:10,510 --> 00:17:06,230
but it became a very interesting project

365
00:17:15,220 --> 00:17:10,520
about critics over cycles from Saanich

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Inlet is an anoxic seasonal Basin that I

367
00:17:18,660 --> 00:17:17,510
visited Effingham is sick cynic and for

368
00:17:22,230 --> 00:17:18,670
Miss oxic

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00:17:24,690 --> 00:17:22,240
I was at sandwich English I just came

370
00:17:27,780 --> 00:17:24,700
back about two weeks ago I was doing

371
00:17:29,970 --> 00:17:27,790
field work there it was a lot of fun it

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00:17:33,690 --> 00:17:29,980
was a great experience

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we collected anoxic sediments as we can

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00:17:40,650 --> 00:17:37,210
see here this is really gooey sediments

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00:17:44,070 --> 00:17:40,660
and really black and they had this very

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00:17:46,200 --> 00:17:44,080
rich like rotten egg smell to it so

377
00:17:49,020 --> 00:17:46,210
there's a lot of silt by in here which

378
00:17:51,270 --> 00:17:49,030
is great unlike my son of Monica Basin

379
00:17:54,720 --> 00:17:51,280
sediments which smell like nothing so uh

380
00:17:56,130 --> 00:17:54,730
it's very encouraging to to find pyrite

381
00:17:58,440 --> 00:17:56,140
here there should be a lot of pirate

382
00:18:02,130 --> 00:17:58,450
here because it's very anoxic and this

383
00:18:03,570 --> 00:18:02,140
is how I how I extracted the sediment so

384
00:18:06,690 --> 00:18:03,580
these are anoxic they need to be

385
00:18:08,790 --> 00:18:06,700
extracted in a glow bag perch with

386
00:18:10,530 --> 00:18:08,800
nitrogen gas so they don't come in

387
00:18:13,740 --> 00:18:10,540
contact with oxygen because once they do

388
00:18:21,140 --> 00:18:13,750
they get they get oxidized and the

389
00:18:23,100 --> 00:18:21,150
chemistry will change Megan okay so I

390
00:18:26,130 --> 00:18:23,110
just came back so I don't really have

391
00:18:29,190 --> 00:18:26,140
any data to show you about that but I do

392
00:18:30,960 --> 00:18:29,200
have my methods of what I plan to do so

393
00:18:34,950 --> 00:18:30,970
now I have my sentiments I also

394
00:18:38,160 --> 00:18:34,960
collected bottom water bottom waters

395
00:18:41,000 --> 00:18:38,170
from it so I have waters that I'm gonna

396
00:18:44,640 --> 00:18:41,010
study the trace elements as well as

397
00:18:46,560 --> 00:18:44,650
sulfur I have the sediments poor waters

398
00:18:48,390 --> 00:18:46,570
from the side of man some or all of them

399
00:18:50,850 --> 00:18:48,400
I'm gonna study the trace elements in

400
00:18:52,320 --> 00:18:50,860
sulfur and then I'm gonna extract the

401
00:18:54,060 --> 00:18:52,330
pirate from it and I'm gonna do

402
00:18:57,390 --> 00:18:54,070
something similar to this image here

403
00:18:58,920 --> 00:18:57,400
which I'm gonna do a transect and look

404
00:19:02,520 --> 00:18:58,930
at the trace elements and sulfur

405
00:19:04,460 --> 00:19:02,530
isotopes in situ to see what it tells us

406
00:19:07,020 --> 00:19:04,470
and we have done this in the past

407
00:19:10,680 --> 00:19:07,030
pyrite grains and it's really hard to

408
00:19:12,720 --> 00:19:10,690
make any assumption try to come with any

409
00:19:15,060 --> 00:19:12,730
interpretation on it and that's why I

410
00:19:17,250 --> 00:19:15,070
want to do modern because in modern I

411
00:19:19,640 --> 00:19:17,260
can look at the sediments the poor

412
00:19:22,650 --> 00:19:19,650
fluids the waters and really understand

413
00:19:25,800 --> 00:19:22,660
what is the relationship between all of

414
00:19:26,780 --> 00:19:25,810
that and between the pyrite grains and I

415
00:19:30,230 --> 00:19:26,790
think I'm out of

416
00:19:32,560 --> 00:19:30,240
so here's thank you to everyone that has

417
00:19:34,920 --> 00:19:32,570
helped me all the funding agencies and

418
00:19:39,040 --> 00:19:34,930
open to questions

419
00:19:48,550 --> 00:19:39,050
[Applause]

420
00:19:53,720 --> 00:19:51,380
first of all thank you for your very

421
00:19:56,750 --> 00:19:53,730
recent talk so my question is more a

422
00:19:59,120 --> 00:19:56,760
curiosity and the pirated is form

423
00:20:01,220 --> 00:19:59,130
pyrogen Italy is possible to find

424
00:20:05,420 --> 00:20:01,230
organic matter there that could be used

425
00:20:10,430 --> 00:20:05,430
to further assess that biodiversity so

426
00:20:13,460 --> 00:20:10,440
yes but it's mostly in very modern pie

427
00:20:16,910 --> 00:20:13,470
right once it goes through diagenesis it

428
00:20:19,190 --> 00:20:16,920
starts to lose that shield of organic

429
00:20:20,840 --> 00:20:19,200
material so that's why I'm not even

430
00:20:23,690 --> 00:20:20,850
looking at organic material because I am

431
00:20:27,890 --> 00:20:23,700
curious about the diagenesis and how it

432
00:20:29,540 --> 00:20:27,900
gets preserved and I just had a quick

433
00:20:31,580 --> 00:20:29,550
question so when you were looking at

434
00:20:33,560 --> 00:20:31,590
like the accuracy of the various ones

435
00:20:35,810 --> 00:20:33,570
that look like the metamorphic was like

436
00:20:38,030 --> 00:20:35,820
really good for all of them yeah versus

437
00:20:39,740 --> 00:20:38,040
the other is there a reason why that's

438
00:20:43,070 --> 00:20:39,750
more accurate there definitely is the

439
00:20:45,620 --> 00:20:43,080
reason so during metamorphic processes

440
00:20:48,520 --> 00:20:45,630
you can think of like magmatic processes

441
00:20:51,230 --> 00:20:48,530
for example when the pirate is four mean

442
00:20:54,500 --> 00:20:51,240
it's taking out all of the trace

443
00:20:57,070 --> 00:20:54,510
elements that were before so it has very

444
00:21:00,020 --> 00:20:57,080
very low amounts of trace elements about

445
00:21:03,100 --> 00:21:00,030
parts per trillion of trace element so

446
00:21:07,190 --> 00:21:03,110
that's why it's very good on just like

447
00:21:08,850 --> 00:21:07,200
telling that one apart alright let's