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goodmornin last talk of the morning I'll

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try and keep it short and sweet it's

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good to be back at a grad calm seen

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bunch of old friends making some new

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friends even some new enemies Team

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Rocket for those of you who don't know

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they won trivia last night so yeah I'm

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going to be presenting some of my

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Master's work at the University of

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Cincinnati I'm transitioning now to a

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PhD at UCLA so talk a little bit about

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what I did and what I'm transitioning

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into and what I'd like to work on in the

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future solo vocab check for you we were

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all different disciplines here chemist

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physics biologist geologist so just to

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make sure we're all on the same page

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carbon isotopes I like that a couple

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people have talked about this before so

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some of this is a little bit review but

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it's basically a ratio of carbon-13 to

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carbon-12 and that's in Delta notation

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typically you can do it on perform this

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bio signature so and in this talk it's a

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mostly focus on evidence of past life

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precambrian is basically any strata that

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are older than 500 41 million years ago

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organics in the context that I am

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talking about them are mostly aromatic

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hydrocarbons that have been produced

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over billions of years in other words

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carriage in which I'll discuss in a

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minute and by metabolisms I'm

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specifically talking about microbial

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carbon fixation pathways so there's a

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lot of other microbial metabolism spoke

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them to focus explicitly on carbon here

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today so when we're measuring carbon

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isotopes an organic matter what you're

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looking at is our game air that's been

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produced over billions of years in the

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Precambrian mostly and it comes from

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originally from biopolymer so bio

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molecules that are made in microbes and

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basically when they die they get broken

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down through microbial degradation in

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the monomers and eventually into through

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polymerization condensation reactions

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turn into geo polymers which is

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basically a very high molecular weight

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in saw you in soluble in organic

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solvents

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it makes up about ninety-five percent of

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organic matter well caveat is that this

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goes through a whole large range of

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history so it goes through diagenesis

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which is basically everything that

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happens prior to burial then it gets

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buried deep down and so as you go down

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in in the strata you're going up in

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temperature and pressure eventually

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leading the electrification and in some

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cases metamorphism which all these

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things can have to an extent an effect

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on the carbon isotope signature so how

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do we detect carriage inn in Precambrian

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rocks I like that someone else already

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went through ramen so I don't have to

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explain too much but basically this is

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your carriage and shift in your in your

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raman spectra so when you see this

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pop-up you have a pretty good feeling

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that you're looking at organic matter

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that was biologically produced so

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basically what Raman spectroscopy does

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is it allows you to measure this on the

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micron scale so you can measure this

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actually on individual microfossils so

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that's what we'll get into here in a

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second and you can do it institue in the

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thin section so you know that you have

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to extract anything you just throw a

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microscope slide underneath the

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underneath there and Zack with the laser

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and you know what you got also it's been

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shown bill shopping 2005 and others in a

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paper that was showing that you can

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quantitatively express the relative

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thermal maturity of of the kerogen so

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someone else showed raman earlier and

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said oh this is into geochemical

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immature and that's basically what he's

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referring to is comparing this sweet and

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so he uses what's called the r.i.p value

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so we did a little bit of that work in

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my masters and it's kind of

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counterintuitive low geochemical

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maturity is a high r.i.p value and this

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stuff down here is really cooked almost

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almost like graphite so carbon isotopes

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just a little bit more kind of

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background stuff I said you could do it

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in carbon and in organics so carbonate

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or organic carbon here's the pretty

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equation for all your math people and

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then you what you can do is you can

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measure in the inorganic source and the

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organic source take the difference and

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that basically gives you the total

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metabolic

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for the biomass and so that's basically

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what's mainly used when you are

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inferring microbial carbon fixation

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pathways in the Precambrian is you're

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using this difference from the organic

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source to the inorganic source the catch

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is is that various metabolic pathways of

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microorganisms fraction eight carbon

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isotopes differently and to a different

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extents so that's what's shown on this

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plot here adapted from Manfred should

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Lasky in 2001 and circle at all in 2005

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so what this basically shows is average

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compositions for the inorganic species

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in the black so you have a marine carbon

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a bicarbonate atmospheric co2 develop

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co2 all roughly between zero and

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negative 10 so what carbon and carbon

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isotope terms that's relatively heavy as

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opposed to these microbial fixation

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pathways which fraction eight carbon to

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a much greater extent so anywhere from

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negative ten to negative 35 for most

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cyanobacteria photosynthetic organisms

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and when you get down into

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methanogenesis and especially methane a

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trophy so methane cycling can really

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deplete carbon isotopes quite a ways so

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when we look at this in the geologic

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record this difference between the

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organic species in the inorganic species

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is notable all the way back three and a

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half billion years potentially even 23.8

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so some of you might be familiar with

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the issue I met a sedimentary sweet so

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this is showing the organic carbon

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measured the range of it and this is

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showing carbon isotopes that have been

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altered by metamorphism so the

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metamorphism tends to drive things

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towards more heavy values and you'll

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notice actually that the carbonate

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values are depleted as well these long

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bars here what they represent our iron

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ion microprobe measurements in appetite

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grains which show that the graphite in

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there has actually been preserved

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differently than it has elsewhere in the

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rock so there is some some suggestions

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that

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carbon isotopes and carriage in might be

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preferentially preserved in certain

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minerals we've seen that in albeit and

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it appears to be so in courts as opposed

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to something like a carbonate one thing

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to note was just talking about how

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methane cycling can really deplete these

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carbon isotopes that's what's thought to

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have occurred here at the Fortescue

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corrosion excursion 2.7 billion years

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ago when you saw a large may possibly

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evolutionarily advancement of methane

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cycling metabolisms I think that's a

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pretty cool thing so looking into

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archaean one thing I work on is

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microfossils so we tie a carriage inn

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and carbon isotopes to microfossils to

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try and better understand very early

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evolution of life these are all the

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known microfossil occurrences in the

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archaean record so it's a few dozen so

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anything you find nowadays is a huge

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contribution to this so most of these

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things are relatively small less than 50

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microns but there have been more

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recently found some of these larger

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Lloyd things which are exceptionally

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large for the Precambrian and

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particularly the archaean record where

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they get up to 300 microns in diameter

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the heck are those things is a good

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question so here's just another way of

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portraying that this is just some images

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collected some from chef at all 2007 and

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some of these new extra large

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Lloyd's discovered by sujit ani at all

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in 2010 and jabot at all in 2010 2010

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was a good year so we mostly filaments

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small Lloyd's some of these kind of

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bacillus shaped things and and really

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they're so simple the morphologies are

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so simple that you have a very hard time

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tying it back to a modern microorganism

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saying yeah that's what it is oh that

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filament oh yeah it's a sulfur oxidizing

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bacteria no doubt about it so we need to

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find other methods of finding evidence

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to explain basically the paleo ecology

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of these of these fossils and one way

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you can do that is with carbon isotopes

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so some of my work at UC in Cincinnati I

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was also working in the

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a cat Val kraton from South Africa the

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2.5 two billion year old upper gamma han

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formation which is part of that can bail

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Ram Campbell ran super group and it's

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basically the distal portion of that of

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that carbonate platform and so what we

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found where we found these pretty large

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things you scale bars here are 50

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microns so they're relatively large but

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on average 100 25 microns in diameter

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all the way up to like 265 and so when

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we view them transverse to the bedding

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plane you can see that they're actually

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preserved and somewhat show kind of

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almost a resistance to compaction

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between individual layers of sediment

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which was a pretty interesting

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taphonomic feature when you basically

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slice along one of these layers you're

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looking at it from the top down and you

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get a much better idea of how spherical

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this thing is my adviser always like to

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say it's like a like a beach ball so it

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wasn't like it used to be this big large

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sphere but it's gotten all the the

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pressure out of it and it's flattened

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and you can move it around you can twist

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it fold it and that those are the kind

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of things that we think are happening

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here also when you're viewing them in

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these bedding planes you can see some of

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these filamentous microfossils so

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something we started to speculate about

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was whether we might be seeing two

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different communities one a benthic

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chemosynthetic 1 and 1a planktonic

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photosynthetic one but based on

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morphology you can't say that alone so

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what you need to do is you need to plug

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into carbon isotopes and thankfully

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nowadays Sims has become a very useful

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technique for doing this so we can use

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raman to measure the carriage in on a

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micron scale of an individual

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microfossil and then pair that with

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carbon isotope evidence of an individual

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microfossil this has been done pretty

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extensively over the last few years

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willeford at all in 2013 published this

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lovely paper and so what you can see

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basically is they noted to microfossils

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with different morphologies and they

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wanted to say okay do they have a

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similar carbon carbon isotope signature

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so when they measured them they notice

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that these ones are roughly negative 29

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these ones are roughly negative 22 so

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this suggests that there was a slightly

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different carbon fixation pathway that

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existed within these things

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and so that's what we're looking to find

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out we did both carbon isotope

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measurements on these things we

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extracted the carriage and put it in a

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mass spec and we've got about negative

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35 so if you remember that chart earlier

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that's kind of at the tail end for

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photosynthesis it's a very extreme

281
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depletion for purely photosynthetic

282
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which are more typically around negative

283
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25 so the question then is do we have

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two populations a photosynthetic one and

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an Tibet and a benthic chemosynthetic

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one so we'll be going to university of

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wisconsin-madison to work with john

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valley and do some some sims analyses on

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these things wouldn't be right if I

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didn't come to astrobiology conference

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and didn't talk about Mars so a lot of

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this research does have implications

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going forward particularly for sample

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return I think but curiosity has already

295
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detected some organic compounds which is

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great because that wasn't even its

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primary mission so it's just stumbling

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upon these things and now we have March

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2020 which is much more directed at

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searching for organics and signs of life

301
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and sample return is something that I

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think a lot of us very much hope to be a

303
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part of it be really really neat to get

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them back and throw the kitchen sink

305
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atom here and so I think that what we're

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trying to do now is use ramen in the

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deep UV which is this Sherlock

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instrument which will be on 2020 and we

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want to look at organics in things our

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known biological organic matter and if

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we can see what those look like in the

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deep UV on earth then if we if we see

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that on Mars with Sherlock then we'll

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have a good idea of what samples we want

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to snag up and cash for later and who

316
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knows what the Europeans are doing so

317
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yeah fine life's in organics is

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difficult there's other ways that you

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can produce organic matter that is

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carriage and like and depleted in carbon

321
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isotopes right so just those two things

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alone you can't say biologically for

323
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sure you really have to take a holistic

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approach and that's going to take a lot

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more research one thing I'd like to do

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my PhD is look at these different forms

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of organic matter and try and see if

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there are some characteristic

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differences in them that we might be

330
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able to discern the biogenesis V of any

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organic matter we detect on Mars which

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be awesome so how do we determine a

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biotic first biological synthesis of

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organics that's the big question I think

335
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right now in terms of in terms of this

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so with that I'd like to acknowledge my

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advisor my community a thesis committee

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my funding sources and absolutely the a

339
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grad con organizers great job guys

340
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appreciate questions for Jeff if you're

341
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looking at your sedimentary samples from

342
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2.5 billion years ago how prevalent are

343
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these features in them do you have to

344
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look really hard or just slice it open

345
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and they're pretty abundant in their own

346
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there so I features I think your talk

347
00:14:24,580 --> 00:14:21,920
about the microfossils yeah exactly okay

348
00:14:30,120 --> 00:14:24,590
so searching for microfossils is a very

349
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painstaking a thing to do it is so

350
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sometimes you'll go through 300 thin

351
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sections and not see a thing sometimes

352
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you'll pop one in there and it's just

353
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filled so in this case they were pretty

354
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isolated we probably went through 20 or

355
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30 thin sections maybe 20 and found may

356
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be 100 150 micro souls so and most of

357
00:14:53,680 --> 00:14:51,950
them aren't that well preserved they

358
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don't look that good so I put up the

359
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ones that look nice so we can all do you

360
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know how that compares to like more

361
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recent millions of your old Michael

362
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microfossils just trying to get an idea

363
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of abundance from back then compared to

364
00:15:10,180 --> 00:15:07,880
modern day in terms of abundance um well

365
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I think you have a lot more life well

366
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yes actually wonder if it's easy if you

367
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see the smaller the earth so there's

368
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more likelihood that you're going to

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have microfossils preserved but really

370
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what it comes down to is the

371
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preservation ille processes so

372
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microfossils in the Precambrian are

373
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really only preserved when you have

374
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early silica replacement and you have

375
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this trip formation that basically it

376
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traps every

377
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before the carbonate grains can grow

378
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large enough to break everything apart

379
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so you really need early diagenetic

380
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silica replacement to preserve

381
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microfossils which was much more common

382
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in the Precambrian when the oceans were

383
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super saturated with silica but now you

384
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have organisms in the oceans and the

385
00:15:54,579 --> 00:15:51,230
waters that are secreting silica taking

386
00:15:57,460 --> 00:15:54,589
it out so it just it's just not it's

387
00:16:07,030 --> 00:15:57,470
just not a prevalent process nowadays

388
00:16:08,319 --> 00:16:07,040
okay thank you yeah actually have a

389
00:16:12,430 --> 00:16:08,329
simple preparation question I'm

390
00:16:15,460 --> 00:16:12,440
wondering the prep your samples for an

391
00:16:18,790 --> 00:16:15,470
epic analysis and ramen can you utilize

392
00:16:20,170 --> 00:16:18,800
the same thin section or can you talk a

393
00:16:23,350 --> 00:16:20,180
little bit about that in terms of the

394
00:16:25,509 --> 00:16:23,360
sim preparation and ramen okay ramen is

395
00:16:27,930 --> 00:16:25,519
a lot easier than sims that's for dang

396
00:16:31,629 --> 00:16:27,940
sure i will learn that the hard way

397
00:16:33,460 --> 00:16:31,639
ramen is non-destructive so it's you can

398
00:16:35,230 --> 00:16:33,470
zap it and it won't do anything to it

399
00:16:36,790 --> 00:16:35,240
unless you zapped it with a deep UV

400
00:16:38,530 --> 00:16:36,800
laser that's some of the problems that

401
00:16:42,069 --> 00:16:38,540
are having with Sherlock is that it can

402
00:16:43,660 --> 00:16:42,079
alter the sample but in the visible

403
00:16:45,879 --> 00:16:43,670
wavelengths we were using it doesn't

404
00:16:47,470 --> 00:16:45,889
alter the sample at all so you can hit

405
00:16:49,449 --> 00:16:47,480
it with ramen but once you hit it with

406
00:16:50,590 --> 00:16:49,459
the sims it's ablating it so you're

407
00:16:54,250 --> 00:16:50,600
gonna you're going to lose some material

408
00:16:59,710 --> 00:16:54,260
there you can use the same themes in

409
00:17:01,389 --> 00:16:59,720
same thin section yeah okay let's think