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[Music]

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alrighty hi everyone thanks for having

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me today my name is Michaela Liang I'm

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currently a PhD candidate at the

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University of California Riverside

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um I'll be talking to you today about my

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work on novel methylated biosignatures

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and specifically their application to

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exoplanets which I usually don't have to

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say because I'm usually talking to

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astronomers so that's kind of fun

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um there's a little bit of a breakdown

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diagram here on the far side that's my

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left so your right

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um that's kind of showing the processing

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of these molecules all the way from

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surface fluxes atmospheric chemistry

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um the production of spectral features

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and we're kind of thinking about how

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this will vary across a variety of

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Stellar types so that's kind of just a

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very quick summary breakdown

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um so let's jump into talking about why

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we're specifically interested in these

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methylated gases um and the the answer

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is largely that there's a major false

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positive problem

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um for the first biosignature detections

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a lot of molecules

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um Like Oxygen ozone methane things like

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that that we expect to be potentially

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the first molecules detected

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um that could be connected to life in

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terrestrial exoplanet atmospheres can

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also be produced by a variety of

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planetary processes including

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thermodynamic equilibrium chemistry

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um and so these methylated gases are

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specifically uh almost exclusively

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produced by life and all of the other

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Pathways that we've investigated have

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been very minimal so we're really

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excited that these gases could

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potentially be a very strong affirmative

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uh signal of life and these gases are

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generated by the process of volatile

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methylation which actually we believe to

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be a descendant or perhaps a Rel

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relative in some way of the process of

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DNA methylation which for you biologists

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out there I'm sure you're all much more

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familiar with than I but we see volatile

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methylation in a variety of different

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ecosystems including microbial mats the

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open ocean and primarily actually a lot

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of terrestrial Marine uh kind of

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crossover ecosystems

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um we also see it done by a variety of

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organisms primarily a single cellular

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life but we do also see everyone's

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favorite Brassica vegetables

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um also produce methylated gases

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um and we think in particular that

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methylation is connected to the process

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of environmental detoxification

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um and that the Need For Life to kind of

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control its environment is possibly a

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fundamental characteristic of life

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itself and so when we're thinking about

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you know what life might look like under

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fundamentally different biogeochemistry

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um you know we're it's probably still

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going to need to be controlling that

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surroundings in some ways we're really

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excited about that potential tie-in as

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well

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um we're not the first people to think

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about methylated biosignatures there are

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uh previous study specifically cigarette

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all 2005 and domigal Goldman at all 2011

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which specifically show one an enhanced

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buildup level around M dwarfs and two a

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secondary ethane biosignature that's

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produced by atmospheric photolysis of

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dimethyl sulfide and dimethyl disulfide

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and that produces a potentially

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detectable ethane signature

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um and so we're going to follow a

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relatively similar uh pathway we're

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jumping from labland that we've been in

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for the last couple of talks to modeling

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land

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um and uh primarily we're going to be

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talking about photochemical and spectral

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modeling basically thinking about how

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these gases are processed in the

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atmosphere and what those potential

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signals might look like

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um just jumping into some results

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um we have first here methyl bromide

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which is again on your left and we have

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methyl iodine which is on I think you're

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right

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um and you'll notice that as I said

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before for methyl chloride they see an

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atmospheric buildup level that's much

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higher around these M dwarf uh cooler

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better stars and we actually see that uh

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buildup replicated and actually even

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more enhanced for methyl bromide and

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this result from methyl is from like

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literally last week so that's brand new

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um and we're also seeing again the same

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sort of enhanced buildup you'll notice

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that it's to a lesser degree and we

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think that's probably because it's just

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a larger molecule and so it's a larger

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molecule it's going to be hit by more uh

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potentially active uh photochemical

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light

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so we use this photochemical model to to

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create profiles of gases in the

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atmosphere and kind of figure out where

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everything is where where it's at in the

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atmosphere and then we're using like I

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said a series of spectral models

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um so this these are mid-infrared

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emission Spectra

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um and the most important thing that

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I'll call your attention to here there's

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kind of a lot going on but the bottom

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row is actually showing an experiment

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that we did where we add multiple

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methylated gases in this case methyl

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chloride and methyl bromide and you'll

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actually notice that the features that

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we see especially for Proxima Centauri

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which is going to be that plot all the

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way down in the bottom corner

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um that feature is actually a little bit

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wider and a little bit deeper than just

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kind of the simple sum of the features

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and that's partially because we're doing

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self-consistent photochemistry

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um and so you do get higher buildup

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levels and also because this absorption

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feature near 10 microns is actually the

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acetah halogen Bond and so acetochlorine

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and Cedar bromine are sort of uh next to

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each other and overlapping a little bit

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but really creating this much larger

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feature um so we're optimistic that a

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future telescope capable of minimum

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infrared emission spectroscopy could

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detect these

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and we also think that while this could

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detect a methylated gas we could

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potentially fingerprint a specific

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methylated gas using extremely high

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resolution ground-based spectroscopy

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um and potentially one mode that we

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could use for the emission spectroscopy

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that I was just showing is the life

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telescope which is a concept Mission

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that's actually run by the European

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Space Agency where they're using

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interferometry to essentially get a

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larger uh approximation of a telescope

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rather than putting like 100 meter

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telescope in space because that's

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actually going to be very difficult to

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do

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um and so you could see here that

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there's simulated error bars for the

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observations

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um and that there's kind of a noticeable

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difference between the atmospheres

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without these methylated gases and

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especially the higher flux cases and we

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can also look at this as a kind of

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comparison to the sigma of the detection

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and you can see we get some pretty

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significantly large features here and

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we're optimistic again that if any bio

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signatures are detected on these planets

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these are very optimistic planets were

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simulating for but hopefully these

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methylated gases will be among uh those

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bio signatures that it's possible to

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detect so I will leave you with my

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conclusions I think I am right on time

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um I'm at poster nine which is right on

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the other side of this wall or you can

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feel free to contact me my information

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is on the slide