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[Music]

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because hi everyone my name is Maggie

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Thompson I am a graduate student at UC

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Santa Cruz it's a real honor to be here

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today to get to tell you all about the

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meteorite outgassing experiments that I

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have been doing over the last year or so

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in the lab and how these can inform

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chemical abundances of super earth and

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other lower mass rocky planet

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atmospheres of course I'd like to take a

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moment to thank my collaborators it's

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not intimidating at all to go right

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after my adviser Jonathan Fortney and

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Miriam Telus though that UC Santa Cruz

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and others including Laura Schaeffer who

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we will hear from later this afternoon

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and others who helped make this work

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possible to start here's a brief road

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map of where we're going for the next

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few minutes I'm going to start by

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discussing the different possible

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formation mechanisms for super earth and

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other lower mass planet atmospheres and

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also talk about some of the assumptions

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that we typically put in our models for

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what these atmospheres are likely made

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out of then I'll motivate how meteorites

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can help inform the initial super earth

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atmospheres that we expect and therefore

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motivating why we're doing experiments

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in the lab and explain our setup then

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I'll discuss some of our current

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experimental results and future work so

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to start how do super Earths obtain

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their atmospheres

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I think clearly this is very much an

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unanswered question and very important

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within the field and it's likely that

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super earths are going to have a wide

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diverse range of atmospheres from what

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we've been talking about earlier this

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morning hydrogen rich primary

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atmospheres that accrete from the

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stellar nebula

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to potentially terrestrial like

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secondary atmospheres that instead form

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via al gassing look here I just have

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some two little schematics yes that I'm

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showing on the top and on the bottom so

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primary is in the red and then secondary

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atmospheres is in the blue and so it's

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likely that a subset of super Earths

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and other low mass exoplanets will

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likely not be able to retain significant

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primary atmospheres of course as we

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talked about with atmospheric escape

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this morning this is super complicated

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but it's so likely that some of them

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won't be able to hold on to them for

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very long and so instead

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secondary atmospheres that form via out

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gassing are going to be important so for

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the remainder of my talk I'm going to be

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focusing on these secondary Alka Singh

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atmospheres

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okay so I think it's been made very

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clear throughout this EXO climb so we're

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at this very exciting next phase in

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exoplanet science where we're pushing to

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being able to characterize the physics

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and chemistry of lower mass super earth

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atmospheres and then one day even

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pushing to rocky planet atmospheres and

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as Jonathan talked a little bit about we

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currently don't have a real first

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principles understanding of how to

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connect a planet's interior or its bulk

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composition to its atmospheric

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properties I think this is especially

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true for these lower mass planets and so

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until we have observational constraints

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that become available that we expect to

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have in the coming years we have to make

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assumptions about what these planets are

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made of and we have to resort to models

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so here I just want to briefly review

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some of the common assumptions that we

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make in terms of what these atmospheres

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are composed of looking at solar

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abundances or some multiple of solar

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abundances or perhaps giving planet

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solar system planet abundances so get a

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take Earth's atmospheric composition and

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put that into our models or also ad hoc

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abundances so sometimes we'll have a

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carbon dioxide dominated atmosphere

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whereas team dominated water atmosphere

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or some ad hoc combination so with that

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in mind I'm now gonna motivate why we

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would want to measure the out gas

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volatiles from meteorites and how this

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can help inform these secondary super or

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lower mass planet atmospheric

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compositions so we believe in general

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that planets in our solar system formed

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out of material that's approximately

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analogous to meteorites I'll talk a

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little bit more about that statement in

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the coming slides and as we just

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discussed some super earth atmospheres

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or lower mass rocky planets are unlikely

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or likely to form their atmospheres

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through outgassing

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during accretion and so therefore if we

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measure the AB gassing composition from

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meteorites this can help inform the

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initial outlast atmosphere compositions

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of soup earth now when I have this this

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little

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I'm addict here I want to point out that

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I'm not making a one-to-one comparison

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here I'm not going to say that one

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particular meteorite this little rock

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that we were lucky enough to have land

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on earth it's going to be exactly what a

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planet is going to be made out of but

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these are the building blocks and so

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this is at least a place to start so

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when I say meteorites what type of

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meteorites am I talking about for those

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that are not as familiar with

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cosmochemistry I just want to briefly

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review that there are two main types of

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meteorites there are those that went

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through a significant amount of heating

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and differentiated and melted and that

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those that didn't so for the work that

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I'm doing I'm focusing on what a type of

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meteorites that we call Kandra if these

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are the ones that did not experience a

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significant amount of heating they are

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believed to be a record of the original

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components that formed planetesimals and

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planets in our solar system and amongst

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chondrites there are other types as well

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I'm focusing on two types the ordinary

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chondrite has the name success these are

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the most common type of chondrite that

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we find on earth they contain oxidized

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and volatile elements and they may have

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formed in the inner asteroid belt

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although this is certainly an active

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area of research within the

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cosmochemistry community then the second

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type are carbonaceous chondrite these

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have up to 20 percent water they have

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the highest proportion of volatiles out

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of the other chondrite groups and they

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are believed to have originated from

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further beyond the asteroid belt again

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still something that people are working

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on studying that distribution so why

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exactly are chondritic meteorites the

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most applicable to super earth

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atmospheric studies so it turns out that

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the volatiles the really heavily

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volatile elements in the earth like

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hydrogen nitrogen oxygen are believed to

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have originated from the same reservoir

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that sourced the parent bodies of the

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chondritic meteorites and so this is

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being evidenced here in this plot from

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marty 2012 where they're plotting the

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isotopic composition of hydrogen

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expressed by the b2h ratio and then the

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isotopic composition of nitrogen and you

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can see in this like dark pink circle

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that the Earth's surface layers so this

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is including Earth's oceans and the

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atmosphere a very

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similar value to if you were to average

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the ordinary and carbonaceous chondrites

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together

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so therefore in general the average

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volatile abundances from ordinary and

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carbonaceous chondrites are pretty

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similar to what we see in Earth's

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atmosphere and surface layers so this is

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a good place to start okay so people

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have been interested in meteorite

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outgassing and its implications for

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planet atmospheres before particularly

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from a theoretical point of view so

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Laura Schaeffer and Bruce Begley in a

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series of papers modeled the thermal

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outgassing from various chondrites using

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chemical equilibrium calculations and so

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here this is some of the results from

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their work where they are showing the

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mole the mole fraction on a log scale so

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you can think of that as abundance as a

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function of temperature and pressure for

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a variety of chondrites and so you're

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seeing here the different gases that

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come off through doing these

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calculations and they've applied these

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calculated outgassing abundances to

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initial terrestrial planet atmospheres

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for instance looking at early Earth and

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what the implication may be for that but

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unfortunately there are no experimental

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data to really constrain these

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theoretical calculations and so that's

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where we come in so this is a schematic

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of the meteorite heating experiments

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that we're doing in the lab this lab is

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a bit bigger than this table but but not

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by a whole much and so what we have is a

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furnace that can go up to 1,200 degrees

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Celsius or 1500 Kelvin we place our

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meteorite sample into this little

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crucible here that little yellow that

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little yellow block and then we heat up

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our sample and we measure it using a

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type of mass spectrometer it's called a

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residual gas analyzer so this is a

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machine that's often used in physics

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labs or various other labs to measure

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and to check your vacuum environment or

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to measure trace amounts of gases and so

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it's particularly sensitive to all the

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different gases that are coming off of

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your sample and so what it measures is

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the partial pressure of different

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species as a function of the temperature

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which you're heating your samples to and

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so for each of our samples we powder

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them

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and so that means literally crushing a

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meteorite sample with an agate mortar

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and pestle in the lab which is very

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exciting for me the first time I got to

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do that and I'm only using 3 milligrams

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per experiment that I run so I'm not

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wasting too many of these very precious

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materials that we have on earth and I'm

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doing all of these experiments at very

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low pressures you can see here around 10

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to the minus 8 bars this is because we

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don't want any contamination that is due

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to just the air in the room and so we're

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trying to be sure that we minimize that

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contamination and we are also doing it

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so that our residual gas analyzer can

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operate properly this is just a brief

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overview of the type of experiments we

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do we tend to first heat up our samples

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to 200 degrees Celsius to get rid of any

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adsorbed water so these meteorites have

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been sitting in earth for quite a number

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of years and so they tend to gain water

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just from Earth's atmosphere that's not

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intrinsic to the sample so we want to

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try to get as much of that off as we can

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and then we heat up to 1,200 degrees

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Celsius over five hours and measure the

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outgassing volatiles that come up so

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here's an example of some of our results

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so this is data that we took for a

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really interesting carbonaceous

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chondrite it's called aguas Arcas it was

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a fall in Costa Rica this year so if

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anybody read in the news it fell on to a

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dog house and the dog is fine but the

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dog was named rocky which is very

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appropriate in my opinion and so this is

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showing you the partial pressure of

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00:10:25,700 --> 00:10:24,540
different gases as a function of

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00:10:28,070 --> 00:10:25,710
temperature that we're heating our

281
00:10:29,900 --> 00:10:28,080
samples to and so you can see though

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00:10:32,510 --> 00:10:29,910
maybe something that's puzzling you is

283
00:10:34,550 --> 00:10:32,520
that for some of these gases we are

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00:10:36,350 --> 00:10:34,560
measuring potentially two different

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00:10:38,390 --> 00:10:36,360
species and so the reason for this is

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00:10:41,270 --> 00:10:38,400
that the mass spectrometer is measuring

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00:10:42,890 --> 00:10:41,280
things by their mass number and so if

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00:10:45,080 --> 00:10:42,900
you look at the periodic table certain

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00:10:48,020 --> 00:10:45,090
species overlap so for instance carbon

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00:10:49,790 --> 00:10:48,030
monoxide and nitrogen have the same mass

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00:10:51,530 --> 00:10:49,800
number which makes it a little bit

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00:10:53,240 --> 00:10:51,540
trickier in our analysis to be sure that

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00:10:55,160 --> 00:10:53,250
we can disentangle between these two

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00:10:56,360 --> 00:10:55,170
that's part of the thing that we are

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00:10:59,780 --> 00:10:56,370
working on and trying to really

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00:11:02,600 --> 00:10:59,790
understand this data so we can now

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00:11:04,700 --> 00:11:02,610
compare our experimental results to

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00:11:07,010 --> 00:11:04,710
theoretical studies and so here

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00:11:09,170 --> 00:11:07,020
showing you this is now mole fraction as

300
00:11:11,030 --> 00:11:09,180
a function of temperature these are

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00:11:12,980 --> 00:11:11,040
theoretical chemical equilibrium

302
00:11:15,200 --> 00:11:12,990
calculations courtesy of Laura Shafer

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00:11:16,970 --> 00:11:15,210
that were conducted for the same

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00:11:19,010 --> 00:11:16,980
meteorite sample that we measured in the

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00:11:21,020 --> 00:11:19,020
lab under these same low pressure

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00:11:22,820 --> 00:11:21,030
conditions if you'll notice there's a

307
00:11:25,370 --> 00:11:22,830
lot of different things that come off

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00:11:27,350 --> 00:11:25,380
I'm bolding the ones that we have

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00:11:28,880 --> 00:11:27,360
measured in our experiment we're limited

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00:11:31,160 --> 00:11:28,890
with our mass spectrometer we can't

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measure infinim infinite number of

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00:11:35,510 --> 00:11:34,140
species at a time so the bold ones are

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the ones that match the stuff that we've

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00:11:40,070 --> 00:11:37,770
measured and so then here are our

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00:11:42,020 --> 00:11:40,080
experimental results and so I'm just

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00:11:44,540 --> 00:11:42,030
gonna briefly touch on some similarities

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00:11:46,910 --> 00:11:44,550
and differences between these two the

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00:11:49,280 --> 00:11:46,920
main similarity that you'll notice is

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00:11:51,380 --> 00:11:49,290
that water is the dominant species that

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00:11:53,930 --> 00:11:51,390
is outgassed almost over almost all

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00:11:56,270 --> 00:11:53,940
temperature ranges not all you'll also

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00:11:59,990 --> 00:11:56,280
notice that our carbon monoxide nitrogen

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00:12:02,620 --> 00:12:00,000
trend is fairly similar in both cases

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00:12:05,900 --> 00:12:02,630
one interesting result is hydrogen

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00:12:07,360 --> 00:12:05,910
sulfide has a similar outgassing trend

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00:12:10,430 --> 00:12:07,370
but ours peaks at a higher temperature

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00:12:12,730 --> 00:12:10,440
and this could be due to the phase that

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00:12:15,230 --> 00:12:12,740
sulfur is locked in in these meteorite

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00:12:17,540 --> 00:12:15,240
minerals and having to undergo a phase

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00:12:18,950 --> 00:12:17,550
change in order to out gas so there's a

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00:12:20,660 --> 00:12:18,960
lot of different things that we have to

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00:12:23,180 --> 00:12:20,670
unpack here but this is just an example

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00:12:25,250 --> 00:12:23,190
of some preliminary results of course

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00:12:27,350 --> 00:12:25,260
you'll notice some differences one of

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00:12:30,650 --> 00:12:27,360
the main ones being that hydrogen gas is

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00:12:32,900 --> 00:12:30,660
the main it's the second most abundant

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00:12:34,880 --> 00:12:32,910
species that comes off you'll notice I

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00:12:37,040 --> 00:12:34,890
don't have that here we did measure

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00:12:39,200 --> 00:12:37,050
hydrogen gas but we're not exactly

340
00:12:40,910 --> 00:12:39,210
confident that the hydrogen gas that

341
00:12:43,820 --> 00:12:40,920
we're measuring is actually coming from

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00:12:45,530 --> 00:12:43,830
hydrogen gas and not an fragment of

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00:12:48,290 --> 00:12:45,540
water given the way our mass

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00:12:50,090 --> 00:12:48,300
spectrometer works it's ionizing the gas

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00:12:52,580 --> 00:12:50,100
does that come in and so it might be an

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00:12:55,220 --> 00:12:52,590
ion fragment coming off of water so this

347
00:12:56,930 --> 00:12:55,230
is a lot of just exciting things that we

348
00:13:00,170 --> 00:12:56,940
have to keep working on the main

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00:13:01,790 --> 00:13:00,180
conclusion being that our results are

350
00:13:03,980 --> 00:13:01,800
showing you that in the lab we're not

351
00:13:06,560 --> 00:13:03,990
reaching chemical equilibrium and I

352
00:13:08,210 --> 00:13:06,570
think that that is to be expected and

353
00:13:11,450 --> 00:13:08,220
there's kinetics effects that we have to

354
00:13:13,280 --> 00:13:11,460
take into account so just to close up

355
00:13:15,560 --> 00:13:13,290
just want to briefly discuss some of the

356
00:13:17,390 --> 00:13:15,570
future work I plan to do this includes

357
00:13:17,980 --> 00:13:17,400
performing additional meteorite heating

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00:13:19,870 --> 00:13:17,990
Experion

359
00:13:21,760 --> 00:13:19,880
focusing on the ordinary chondrite i

360
00:13:24,640 --> 00:13:21,770
also want to modify our experimental

361
00:13:26,500 --> 00:13:24,650
procedure to get rid of the amount of

362
00:13:28,780 --> 00:13:26,510
stuff that we are having the water that

363
00:13:30,490 --> 00:13:28,790
gets absorbed at 200 degrees so I want

364
00:13:32,200 --> 00:13:30,500
to hold it there for longer and also

365
00:13:34,510 --> 00:13:32,210
measure some of these other gases like

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00:13:36,280 --> 00:13:34,520
sulfur dioxide and water and things that

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00:13:38,230 --> 00:13:36,290
are predicted to come out in chemical

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00:13:40,840 --> 00:13:38,240
equilibrium calculations and then

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00:13:42,220 --> 00:13:40,850
ultimately we want to place the results

370
00:13:44,800 --> 00:13:42,230
from these experiments in the larger

371
00:13:46,720 --> 00:13:44,810
context of our exoplanet models so we

372
00:13:48,820 --> 00:13:46,730
want to simulate atmospheres that have a

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00:13:50,860 --> 00:13:48,830
proper surface boundary condition that

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00:13:53,380 --> 00:13:50,870
have a prescription to treat outgassing

375
00:13:56,290 --> 00:13:53,390
and secondary atmospheres and have our

376
00:13:57,730 --> 00:13:56,300
abundances informed by these results so

377
00:14:00,130 --> 00:13:57,740
I'll just close with my two take-home

378
00:14:02,140 --> 00:14:00,140
points measuring the out gas volatiles

379
00:14:04,150 --> 00:14:02,150
from a variety of chondritic meteorites

380
00:14:05,650 --> 00:14:04,160
samples and provide experimental

381
00:14:08,140 --> 00:14:05,660
constraints to these theoretical

382
00:14:09,100 --> 00:14:08,150
calculations and ultimately the results

383
00:14:11,470 --> 00:14:09,110
from these outgassing

384
00:14:13,270 --> 00:14:11,480
experiments will help inform the initial

385
00:14:16,060 --> 00:14:13,280
boundary conditions on these low mass

386
00:14:17,900 --> 00:14:16,070
planet atmosphere compositions thank you

387
00:14:24,249 --> 00:14:17,910
he'll take

388
00:14:39,769 --> 00:14:37,639
Thank You Maggie um if I remember

389
00:14:42,050 --> 00:14:39,779
correctly and probably Laura knows this

390
00:14:45,259 --> 00:14:42,060
better than I do but in their paper into

391
00:14:48,650 --> 00:14:45,269
in 2004 they do compare with experiments

392
00:14:50,420 --> 00:14:48,660
and then fine very good much with with a

393
00:14:52,220 --> 00:14:50,430
certain between the experiments and the

394
00:14:54,139 --> 00:14:52,230
model so I'm wondering what's difference

395
00:14:55,879 --> 00:14:54,149
between I mean they were not using

396
00:14:57,470 --> 00:14:55,889
meteor eyes they were using rocks from

397
00:14:58,970 --> 00:14:57,480
the earth but they do compare with

398
00:15:00,410 --> 00:14:58,980
friends and so that's certainly true

399
00:15:02,840 --> 00:15:00,420
people have definitely heated up

400
00:15:04,759 --> 00:15:02,850
meteorites before but no one has done it

401
00:15:07,009 --> 00:15:04,769
in such a way at looking at this goal in

402
00:15:08,360 --> 00:15:07,019
mind so a lot of the old older meteorite

403
00:15:10,249 --> 00:15:08,370
heating experiments are trying to

404
00:15:12,259 --> 00:15:10,259
understand what happens when meteorites

405
00:15:14,090 --> 00:15:12,269
enter the Earth's atmosphere so they're

406
00:15:16,850 --> 00:15:14,100
looking at like flash heating really

407
00:15:18,439 --> 00:15:16,860
rapid heating events and so yeah so some

408
00:15:20,179 --> 00:15:18,449
of the results are similar and that's

409
00:15:22,069 --> 00:15:20,189
really awesome but what we're trying to

410
00:15:24,559 --> 00:15:22,079
do is to try to create an experimental

411
00:15:26,600 --> 00:15:24,569
environment that really replicates the

412
00:15:28,579 --> 00:15:26,610
outgassing process as opposed to just

413
00:15:30,290 --> 00:15:28,589
like doing it from what the

414
00:15:32,269 --> 00:15:30,300
cosmochemistry perspective which was

415
00:15:34,129 --> 00:15:32,279
trying to understand more about like the

416
00:15:36,110 --> 00:15:34,139
specific process the meteorites went

417
00:15:37,100 --> 00:15:36,120
through to get to earth but yes that's

418
00:15:40,759 --> 00:15:37,110
very true well you're definitely not the

419
00:15:44,650 --> 00:15:40,769
first people to heat meteorites okay

420
00:15:49,400 --> 00:15:47,360
Nico and Miguel is there a way that you

421
00:15:50,629 --> 00:15:49,410
can break the mass degeneracy with some

422
00:15:52,670 --> 00:15:50,639
other something other than the mass

423
00:15:54,110 --> 00:15:52,680
spectrometer that's a great question

424
00:15:56,900 --> 00:15:54,120
that's something that we would like to

425
00:15:58,189 --> 00:15:56,910
look at in the future for instance we'd

426
00:16:01,269 --> 00:15:58,199
love to be able to maybe like get a

427
00:16:03,410 --> 00:16:01,279
spectra of the gas as its flowing

428
00:16:05,120 --> 00:16:03,420
there's definitely also ways to break

429
00:16:07,069 --> 00:16:05,130
the degeneracy just within the mass

430
00:16:09,679 --> 00:16:07,079
spectrometer itself like we can look at

431
00:16:11,720 --> 00:16:09,689
a variety of Peaks around say like the

432
00:16:14,090 --> 00:16:11,730
carbon monoxide line to differentiate

433
00:16:15,319 --> 00:16:14,100
what's due to carbon versus nitrogen so

434
00:16:16,579 --> 00:16:15,329
I think we're gonna start with that and

435
00:16:21,740 --> 00:16:16,589
then we're gonna look into some other

436
00:16:25,230 --> 00:16:21,750
experimental setups as well okay thank