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[Music]

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so I was asked to give the geology and

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chemistry warm up talk and I would like

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to just apologize to all the geologists

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in the room to begin with I'm a chemist

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but we'll get through it and you can

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tell me what I got wrong at the coffee

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break and so I'm fairly simple and so

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when I think geology and chemistry

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I think rocks and goo and so will will

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sort of see if that's that's the right

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depiction or not and of course it's not

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so when I actually think about geology

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and chemistry I think of them as setting

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the boundary conditions for life so

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they're providing the environments and

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the possibilities of how things could be

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habitable and what is possible in sort

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of the parameter space of life and

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habitability and I think there are sort

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of multiple boundary conditions we can

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think about in terms of how to go with

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this and I think there's there's

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historical there's what was present on

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an early Earth there's environmental

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what is present now on a different

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planet or what is present now in the

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earth and then there's also sort of more

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fundamental physical boundary conditions

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in terms of thermodynamics and kinetics

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what chemistry can occur and how can it

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occur and so from that I think I mean

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it's sort of your classic bottom-up

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approach in terms of thinking about

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habitability in life but I think it's a

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really powerful tool for getting us

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towards understanding the actual sort of

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physical constraints on on life as well

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and so just to orient everyone to this

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timeline I really like this depiction of

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sort of the earth timeline I'm borrowing

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these slides adapted from Steven

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Freeland you think if you haven't met

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him but there's sort of four major

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geologic eras

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there's the phanerozoic the Proterozoic

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the Archaean and the Hadean and we're

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just gonna walk our way backwards from

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there so I think of the phanerozoic is

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sort of the normal geology part of the

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timeline of Earth

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and so up here really early we have the

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extinction of the dinosaurs and the

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Cambrian explosion and we're gonna be

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hearing from Amanda about sort of

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neoproterozoic geology earth yeah

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geology today and then around here we

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had our earliest multicellular fossil

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and then working our way backwards we

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have the great oxidation event at about

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two and a half million years ago and

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working from there Chloe is going to be

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telling us about possible chemistry that

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occurred from following the great

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oxidation event and then working our way

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even farther backwards we are sort of

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oldest micro fossils and our oldest

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evidence for direct evidence for life

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art about three and a half billion years

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ago and our indirect evidence for life

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is you know somewhere between 3.8 and

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four billion years ago depending on who

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you believe in which which controversies

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you like to pick and this is also around

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the period of the late heavy bombardment

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if you like the idea of a late heavy

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bombardment and really the period we're

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gonna be talking about most for the

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talks in the afternoon suffer in the

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post coffee break session are gonna be

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our prebiotic chemistry talks and

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they're really quite far down on this

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timeline towards the formation of the

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earth and one of the interesting things

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when we're thinking about prebiotic

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chemistry in particular and the

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conditions and the boundary conditions

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for that is that to a large part we no

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longer have a rock record back that far

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because of plate tectonics and because

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of the recycling of material and so

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other than a few sort of de titer

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detrital zircons here and there there

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really are sort of limits on the

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constraints we have from geology and so

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that's really where the realm of the the

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chemist comes in and they get to sort of

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play around with it I whatever

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conditions they want because we're not

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super constrained by actual geology

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[Laughter]

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maybe not but you know and of course we

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can we can also look at this with Mars

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as

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well and so they're also four main

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timeline sort of urates all right I

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don't know anyway four main distinctions

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here where we have the pre na Qian the

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no hockey and the Hesperian and the

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Amazonian my understanding is the sort

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of border between these two is somewhat

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controversial as well and where that

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time should go I'm not entirely sure but

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this is sort of the area where we think

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that Mars would have had some water and

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maybe been more habitable and then this

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is the dry cold Mars of today and so

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we'll be hearing from Jonathan about

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some sort of potential stability of bio

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signatures in the border between the

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Lockean and the Hesperian time line and

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so when we're thinking about

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constraining the conditions we're

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thinking about what might have been

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present in oceans the salinity the ions

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we're also thinking about what was in

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the atmosphere what gases were available

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also where their aerosols or Hayes's or

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things like that what chemistry can that

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provide and also lambs like how much

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land was around and what were the

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minerals and rocks there as well and

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actually we have most of our geology

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talks today are actually more focused on

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sort of atmospheric tracers and looking

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at atmospheric tracers in the yeah and

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of course we have interactions between

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all of these as well and so we're gonna

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be hearing from a different from a few

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different sort of techniques as to how

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we we can think about it so there are

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geologic proxies using elements to sort

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of tell us about oxygen I'm in in this

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case we're gonna be looking at

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fluorescence with Amanda we're gonna be

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looking at some some analog sites and

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isotope fractionation again and so

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because we've heard a lot about isotope

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fractionation I'm not gonna go into that

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and then also sort of more more truly

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chemical ways of modeling reactivity

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what are the sources and sinks of m0 and

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as I said on the early Earth partly

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because we don't have a great rock

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record there's sort of a lack of

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constraints as well for a sort of when

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we're thinking about more traditional

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prebiotic chemistry and

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sort of as Sayid showed yesterday when

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we're thinking about simple to complex

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that's kind of the the main trajectory

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were thinking of with chemical evolution

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and there are a couple ways of thinking

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about complexity and people use

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different terms but when I think about

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it I think of molecular complexity is

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how we go from sort of simple molecules

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to more complex molecules and in

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particular how we do that without

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biology and so we're gonna be hearing

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about that from both David and we're on

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and just because this comes up at every

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ab grad con chemists really like to use

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skeletal structures and not everybody

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knows what that is so here are a few of

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my favorite molecules but basically each

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of these are a carbon so each of the

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sort of triangular shape here is a

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carbon and then there are hydrogen's

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that are sort of redacted hanging off

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the edge here and so C 3 H 4 o 3 is the

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same as this molecule and then when it

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loses a hydrogen its deprotonated and

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that just comes up and you can hydrate

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or you can do hydrolysis depending on

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whether you have a hydrogen or water or

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not on there okay so we've got molecular

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complexity we've got chemical complexity

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what is sort of the hetero genie

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heterogeneity of the mixture that was

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available what are we thinking about so

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there's the foremost reaction of course

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that makes a whole lot of stuff

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including a little bit of ribose and the

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rajah will be telling us about the role

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of heterogeneity and then we also have

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what I would characterize as super

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molecular complexity we'll be hearing

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from all of our organic chemists this

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afternoon about sort of what are the

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larger 3d organization and in particular

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how do we get towards functionality and

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how do we get towards you know maybe

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getting to biology and biochemistry and

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of course we also have to think about if

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you're going from simple to complex what

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are the back reactions and how are we

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going to be breaking down and how we not

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and in particular Jonathan's going to be

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talking about bio signature stability of

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what are these possible back reactions

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and how we might be missing things and

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yeah just in terms of if we want simple

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to complex we have to have sort of

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overall something pushing us towards

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more complex structure

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that generally requires an input of

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energy and in general a sustained sort

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of out of equilibrium system so I can't

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give a talk and not mention the Sun

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because I'm a photo chemist and that's

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my favorite input of energy but we also

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have wet dry cycles that I suspect we

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will be hearing about as well as a nice

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way of sustaining out of equilibrium

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systems and so and then just to remember

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that we have to think about all of this

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chemistry in the context of the

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environment in the context of all of the

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other stuff that's going on and not just

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in optimization terms but also in terms

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of you know just just what is around and

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we can't forget that mixtures are really

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important as well and so I would say

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that our geology talks are roughly

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atmospheres and rocks and that our

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chemistry talks are largely how do we

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avoid goo and so with that we'll move on