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hi my name is sean domigal goldman i'm

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at nasa's goddard space flight center

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although obviously not literally since

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i'm recording this from my home office

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on microsoft teams

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and today i'll be talking about

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biosignatures uh

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biosignature detection i should say via

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remote sensing

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i'll be focusing on exoplanets because

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that's where my expertise lies

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um although some of this will apply to

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ins i'm sorry solar system biosignature

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remote sensing as well

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if you want a more in-depth uh version

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of what i'm going to say today

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or if you'd like a broader cross-section

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of the community's opinions on this or

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take on this i would direct you towards

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this

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special issue of astrobiology volume 18

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number six that's the june 2018 issue

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which was uh an issue that published the

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work from our of the findings from a

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workshop we hosted

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on exoplanet biosignatures um i really

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would would

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can't recommend that strongly enough

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like it you it has a really good

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cross-section of community opinions

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incorporated into it

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uh and like i said much more detail that

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i'm gonna go into today

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i will try to update things a little bit

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at the end of my talk today from where

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we were at the end of that workshop with

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my

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future i mean here are the questions

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that was asked by the science organizing

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committee who i first of all i'd like to

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thank for

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uh inviting me to give this talk i'm

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really happy to be giving this talk to

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this audience at this time i'm glad this

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workshop is happening and i'm

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i'm really honored to be a part of it so

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thank you very much for inviting me

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and also thanks for these questions

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which which really helped frame this

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talk for me

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um and i'm not going to go over them all

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now i'll just cover them one by one

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starting with the top what do we think

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we are looking for when it comes to

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remote detection of biosignatures

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and what we think we're looking for is a

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number of different kinds of bio

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signatures and i'm

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going to demonstrate them with examples

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from earth now for exoplanets we're not

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going to get this level of spatial

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resolution

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just to demonstrate that yeah we can

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we can see the life does remotely

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because we're remotely observing this

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stuff on earth today

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this first example is a map of methane

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on earth which

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is predominantly produced by life and

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which we can sense remotely by building

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an

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orbiter that has instruments that have

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spectrographs that that can detect the

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wavelengths of light that nothing

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absorbs

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and methane is one biosignature you

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could do this with uh for exoplanets

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we've also talked about doing it for

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oxygen or ozone

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for solar system planets methane has

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been proposed as a biosignature as well

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as

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to phosphine which we've heard discussed

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in the literature

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recently and another kind of

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biosignature in addition to the gases

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that light produces

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are the ways that life affects the

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spectrum or the reflectivity of the

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surface

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and that could come in two forms both

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shown here on this

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this one movie um the first is in the

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oceans you could see chlorophyll which

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is a molecule inside the organism

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in this case used for photosynthesis um

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and on land you're seeing what's called

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the red edge effect that's

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associated with the the jump and

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reflectivity caused by plants

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in either case you're kind of detecting

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the organism itself a molecule the

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organism is made of in the case of

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chlorophyll

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or the structure or color of the of the

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organism in the case of the green

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on on land and either way again you can

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detect this remotely if you've got

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a telescope or in this case an orbiter

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that that includes a spectrograph that's

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got the right resolution and

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uh spectral resolution and wavelength

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range to detect the features you're

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looking for

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and then lastly you could in addition to

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looking for the things that life is made

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of or the

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byproducts of metabolism from the

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biosphere that's present

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you could also look for things that a

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civilization that is present on that

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planet isn't uh doing intentionally

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um some of these would use the same

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kinds of techniques and tools

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and platforms that the prior

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biosignatures would use

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uh such as looking for light coming from

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the night side of a planet or looking

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for the industrial pollutants that are

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clearly non-natural or

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perhaps even not uh clearly not from a a

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biosphere but are clearly from an

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industrialized civilization

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um you could look for those things um

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and there's there's other kinds of

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techno signatures you could look for as

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well including

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communication that's intentional or

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that's leakage

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from internal communication inside that

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civilization

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what's interesting to me is a lot of

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those are also

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require some sort of spectroscopy or

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understanding of

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of radiation of different wavelengths

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now i'm going to focus

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on the gaseous pile signatures for two

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reasons one that's

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where my history is and it's where i

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feel it got the most

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uh sort of authority or experience to

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speak from

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and secondly to be frank that's where a

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lot of the

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past history of research has been um i

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want to

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give the impression that i think that

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that's all we should

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focus on in fact i do think there's a

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case to be made to

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focus more on some of the other kinds of

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biosignatures i just mentioned

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but i won't give a lot of attention to

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you later today that's just not

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where my background isn't and it's not

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where a lot of the history in the field

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has been

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so i'm going to dive deeper into gaseous

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biosignatures

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and i'm going to start with just this

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these two takes which are very similar

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to each other but we're done

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independently

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on what makes a good gaseous

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biosignature

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um in both cases you're both in both of

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these

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papers which as far as i know are were

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considered fairly independently

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you've got a number of considerations

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you want the guests um to to pass

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for lack of a better word to to be a

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good biosignature you want it to be

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something that life makes

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you want it to last in the atmosphere

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long enough so that it could build up to

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detectable levels

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and then you want it to be something

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that it either is not made by

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non-biological processes or is all

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discussed in detail later

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where you can rule out the

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non-biological processes that make that

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gas

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the canonical biosignature that's kind

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of historically made it through all of

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those considerations

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is oxygen along with the photochemical

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byproduct of oxygen which is ozone

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it's made by plants you can see it here

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literally bubbling up from a leaf that's

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put under water for a kid's science

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experiment which

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you can do with your kids at home i'm

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planning to do that with mine

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later this summer um and that oxygen

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once it's made by plants can accumulate

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in the atmosphere to

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very high concentrations like to 20

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which is what it

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what it is in today's atmosphere on

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earth and that's detectable across

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interstellar space

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it's also very hard to make oxygen or

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ozone

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without biology producing it because

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it's rapidly destroyed both by

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photochemistry

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and by by photolysis directly and also

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from reaction with other chemicals in

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the atmosphere and if it's being

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destroyed rapidly it needs to be

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produced rapidly to replenish it that

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high flux

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of oxygen to the atmosphere required to

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sustain oxygen or ozone

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at high enough concentrations for

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detection that flux is orders of

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magnitude higher

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than the non-biological fluxes you get

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of oxygen and ozone

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and it's that orders of magnitude

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difference in flux that we think is the

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true biosignature

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now that said there have been some folks

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including myself

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that have tried to look at ways you

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could do that that where you could make

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enough oxygen or ozone

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so that you can detect it across the

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interstellar space

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without any biosphere being present on

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the planet

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uh there's a nice actually that meadows

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paper i quoted a couple slides ago

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uh from 2016 had a nice review

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of the the research into oxygen as a

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biosignature

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and into all these mechanisms that can

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make oxygen

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abiotically without a biosphere present

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on the planet this is the cover image

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from the issue of astrobiology

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in which that appeared and i recommend

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you take a look at that

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now the reason we did that the the that

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we looked at oxygen and ozone we weren't

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just trying to take

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the canonical biosignature down a few

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pegs we were doing it because we wanted

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to understand what the implications of

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that would be for emissions

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oxygen being the canonical biosignature

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along with its its byproduct ozone

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we're kind of at the heart of all all

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the past mission and all the current

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mission designs that we've been making

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for exoplanet spectroscopy missions

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basically

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if you're if you're designing a mission

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to find biosignatures on exoplanets

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you kind of start with uh can it detect

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oxygen

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and or ozone and what we wanted to do is

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if those missions were going to be

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designed around that at least as a

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starting point we'd want them to also be

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able to discriminate

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between planets that had oxygen or ozone

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but were dead

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and those that had oxygen or ozone that

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originated from a biosphere

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and we were able to do that so oxygen

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and ozone we now know that there are

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ways to make it but they're fairly

287
00:08:47,590 --> 00:08:45,600
um limited in the in the the planetary

288
00:08:48,630 --> 00:08:47,600
context and the stellar context in which

289
00:08:50,389 --> 00:08:48,640
that can occur

290
00:08:52,710 --> 00:08:50,399
and let that lets us do things like this

291
00:08:54,310 --> 00:08:52,720
which you don't have to read in detail

292
00:08:55,910 --> 00:08:54,320
but i put it up here to point out that

293
00:08:58,389 --> 00:08:55,920
because we thought

294
00:09:00,310 --> 00:08:58,399
about the ways that a dead planet could

295
00:09:01,190 --> 00:09:00,320
make that canonical biosignature of

296
00:09:03,269 --> 00:09:01,200
oxygen

297
00:09:04,870 --> 00:09:03,279
we now know what other observations we

298
00:09:05,350 --> 00:09:04,880
need to make what order we can make them

299
00:09:07,110 --> 00:09:05,360
in

300
00:09:08,310 --> 00:09:07,120
what wavelength range that implies for

301
00:09:09,430 --> 00:09:08,320
the mission we're looking at and the

302
00:09:10,870 --> 00:09:09,440
spectral resolution for the

303
00:09:13,190 --> 00:09:10,880
instrumentation on that

304
00:09:15,269 --> 00:09:13,200
that that mission as well which means

305
00:09:16,630 --> 00:09:15,279
that if we were to find oxygen or ozone

306
00:09:18,630 --> 00:09:16,640
on an exoplanet

307
00:09:20,150 --> 00:09:18,640
we could have the same mission do a

308
00:09:23,030 --> 00:09:20,160
follow-up observation

309
00:09:25,190 --> 00:09:23,040
to rule out the non-biological pathways

310
00:09:26,630 --> 00:09:25,200
for making oxygen or ozone

311
00:09:28,630 --> 00:09:26,640
and as i'll talk about later we've done

312
00:09:30,310 --> 00:09:28,640
that for other gases as well we've done

313
00:09:31,670 --> 00:09:30,320
it for methane for example

314
00:09:33,590 --> 00:09:31,680
and i think we should continue to do

315
00:09:36,230 --> 00:09:33,600
that as we move forward consider those

316
00:09:37,750 --> 00:09:36,240
non-biological production mechanisms and

317
00:09:39,670 --> 00:09:37,760
then figure out how to discriminate

318
00:09:42,150 --> 00:09:39,680
between the dead planet that makes that

319
00:09:44,630 --> 00:09:42,160
putative biosignature gas and the true

320
00:09:46,790 --> 00:09:44,640
living biosphere that does

321
00:09:48,389 --> 00:09:46,800
and so the next question is where are we

322
00:09:49,990 --> 00:09:48,399
exploring again i'm focused on

323
00:09:52,150 --> 00:09:50,000
exoplanets here in this talk you could

324
00:09:54,070 --> 00:09:52,160
look for remote biosignatures on well

325
00:09:55,750 --> 00:09:54,080
just about any any planet in the solar

326
00:09:56,470 --> 00:09:55,760
system especially the atmosphere bearing

327
00:09:58,310 --> 00:09:56,480
ones

328
00:10:00,150 --> 00:09:58,320
for exoplanets we've got a lot of

329
00:10:02,389 --> 00:10:00,160
choices in in some sense we've got

330
00:10:04,150 --> 00:10:02,399
thousands of exoplanets we've discovered

331
00:10:06,069 --> 00:10:04,160
and there's two considerations that we

332
00:10:08,150 --> 00:10:06,079
put into which ones would be the best

333
00:10:09,829 --> 00:10:08,160
to do to conduct a search for for

334
00:10:11,269 --> 00:10:09,839
biosignatures on

335
00:10:13,430 --> 00:10:11,279
the first is with regards to

336
00:10:16,150 --> 00:10:13,440
habitability and not habitability in a

337
00:10:18,550 --> 00:10:16,160
theoretical sense but in a practical one

338
00:10:19,190 --> 00:10:18,560
i know that the habitable zone term can

339
00:10:22,389 --> 00:10:19,200
be

340
00:10:22,949 --> 00:10:22,399
a little bit um uh of uh off-putting one

341
00:10:25,110 --> 00:10:22,959
to our

342
00:10:27,110 --> 00:10:25,120
colleagues that look uh for for signs of

343
00:10:28,790 --> 00:10:27,120
life or habitable environments

344
00:10:31,590 --> 00:10:28,800
in parts of our solar system that are

345
00:10:33,430 --> 00:10:31,600
beyond that technical habitable zone

346
00:10:35,590 --> 00:10:33,440
um but the reason that the habitable

347
00:10:37,590 --> 00:10:35,600
zone exists is really about

348
00:10:39,190 --> 00:10:37,600
global biospheres we want to look for

349
00:10:41,750 --> 00:10:39,200
global biospheres because

350
00:10:43,509 --> 00:10:41,760
we think that to detect a biosphere

351
00:10:45,750 --> 00:10:43,519
across interstellar space it's going to

352
00:10:46,870 --> 00:10:45,760
have to have a really robust signature

353
00:10:48,550 --> 00:10:46,880
um have to have pro

354
00:10:49,990 --> 00:10:48,560
and for that we think it will have had

355
00:10:52,310 --> 00:10:50,000
to proliferate it all

356
00:10:54,069 --> 00:10:52,320
all across the surface of the world um

357
00:10:55,509 --> 00:10:54,079
and and to be in close contact with the

358
00:10:57,750 --> 00:10:55,519
atmosphere

359
00:10:59,190 --> 00:10:57,760
and so that's why we want a global

360
00:11:01,269 --> 00:10:59,200
liquid water

361
00:11:03,509 --> 00:11:01,279
bearing planet which is what the

362
00:11:05,110 --> 00:11:03,519
habitable zone is really about so if

363
00:11:07,030 --> 00:11:05,120
that term bugs you just do a search

364
00:11:09,350 --> 00:11:07,040
replace of habitable zone four

365
00:11:11,350 --> 00:11:09,360
global biosphere zone or global liquid

366
00:11:13,269 --> 00:11:11,360
water zone and that that's really what

367
00:11:14,630 --> 00:11:13,279
we mean it's about that global

368
00:11:16,710 --> 00:11:14,640
habitability

369
00:11:18,230 --> 00:11:16,720
and so only as some a subset of these

370
00:11:19,990 --> 00:11:18,240
thousands of planets that we found

371
00:11:21,990 --> 00:11:20,000
with kepler and test and ground-based

372
00:11:23,350 --> 00:11:22,000
observations and other observatories

373
00:11:25,030 --> 00:11:23,360
only a fraction are in the habitable

374
00:11:26,470 --> 00:11:25,040
zone and only a fraction are

375
00:11:28,310 --> 00:11:26,480
of the right size to allow for that

376
00:11:31,110 --> 00:11:28,320
global habitability

377
00:11:32,150 --> 00:11:31,120
additionally only some of these planets

378
00:11:34,389 --> 00:11:32,160
are going to be

379
00:11:35,509 --> 00:11:34,399
amenable to follow-up observations and

380
00:11:37,910 --> 00:11:35,519
spectroscopy

381
00:11:40,310 --> 00:11:37,920
the stars are billions of times brighter

382
00:11:42,230 --> 00:11:40,320
than the planets that we want to look at

383
00:11:44,069 --> 00:11:42,240
and in addition to that the planets are

384
00:11:45,590 --> 00:11:44,079
really dim because they're small

385
00:11:47,350 --> 00:11:45,600
not just dim compared to the star

386
00:11:49,590 --> 00:11:47,360
they're just dim overall

387
00:11:51,430 --> 00:11:49,600
period full stop which means you need a

388
00:11:53,509 --> 00:11:51,440
telescope that's really big to collect

389
00:11:56,629 --> 00:11:53,519
the light from that very dim planet

390
00:11:57,670 --> 00:11:56,639
or and or you need a way to leverage the

391
00:11:59,350 --> 00:11:57,680
light of the star

392
00:12:01,990 --> 00:11:59,360
which is brighter to get some

393
00:12:03,829 --> 00:12:02,000
information from the planet itself

394
00:12:05,269 --> 00:12:03,839
all right so ultimately you really need

395
00:12:05,910 --> 00:12:05,279
three things in a mission that's going

396
00:12:08,470 --> 00:12:05,920
to look

397
00:12:09,829 --> 00:12:08,480
at spectroscopy from exo habitable

398
00:12:11,829 --> 00:12:09,839
exoplanets

399
00:12:13,430 --> 00:12:11,839
you need a big telescope you need a way

400
00:12:14,389 --> 00:12:13,440
to cancel out the starlight and then you

401
00:12:16,710 --> 00:12:14,399
need a way

402
00:12:17,430 --> 00:12:16,720
to analyze the spectrum of the light

403
00:12:19,110 --> 00:12:17,440
that has

404
00:12:20,790 --> 00:12:19,120
interacted with the planet somehow its

405
00:12:22,629 --> 00:12:20,800
atmosphere and or its

406
00:12:24,150 --> 00:12:22,639
surface i'll come to the different

407
00:12:25,829 --> 00:12:24,160
techniques for that in a bit

408
00:12:27,590 --> 00:12:25,839
now if you ask me five years ago i would

409
00:12:29,350 --> 00:12:27,600
have said that that we didn't have many

410
00:12:31,190 --> 00:12:29,360
near-term prospects for this

411
00:12:33,670 --> 00:12:31,200
because although we had jwst on the

412
00:12:34,629 --> 00:12:33,680
horizon none of the targets we had were

413
00:12:36,310 --> 00:12:34,639
good enough for that and

414
00:12:37,910 --> 00:12:36,320
we it really would have required perfect

415
00:12:39,670 --> 00:12:37,920
targets and they didn't anticipate us

416
00:12:42,790 --> 00:12:39,680
getting those perfect targets

417
00:12:44,790 --> 00:12:42,800
well about five years ago we did we got

418
00:12:46,470 --> 00:12:44,800
this trappist-1 system which is amazing

419
00:12:48,629 --> 00:12:46,480
in so many ways it has

420
00:12:49,910 --> 00:12:48,639
first off a number of planets which

421
00:12:51,829 --> 00:12:49,920
opens it up to some comparative

422
00:12:53,110 --> 00:12:51,839
planetology investigations which are

423
00:12:54,949 --> 00:12:53,120
really fun regardless of the

424
00:12:57,190 --> 00:12:54,959
biosignature search

425
00:12:58,470 --> 00:12:57,200
it also has a couple of those worlds a

426
00:13:00,629 --> 00:12:58,480
few of those worlds

427
00:13:02,310 --> 00:13:00,639
potentially in the habitable zone or or

428
00:13:04,629 --> 00:13:02,320
that are potentially habitable

429
00:13:07,030 --> 00:13:04,639
and then lastly the system itself is

430
00:13:07,829 --> 00:13:07,040
very close to us and it has a star at

431
00:13:10,550 --> 00:13:07,839
its center an

432
00:13:11,190 --> 00:13:10,560
m type star that's not too bright which

433
00:13:13,110 --> 00:13:11,200
which

434
00:13:14,310 --> 00:13:13,120
lowers the planet the stark contrast

435
00:13:16,069 --> 00:13:14,320
ratio and

436
00:13:18,470 --> 00:13:16,079
all of that makes it really favorable

437
00:13:19,350 --> 00:13:18,480
for observation um again five years ago

438
00:13:21,430 --> 00:13:19,360
i would have told you

439
00:13:23,350 --> 00:13:21,440
i'm not counting on us being successful

440
00:13:25,190 --> 00:13:23,360
here in the near term because

441
00:13:26,550 --> 00:13:25,200
we would have needed pretty much perfect

442
00:13:28,470 --> 00:13:26,560
targets and then

443
00:13:29,829 --> 00:13:28,480
like i said we got these targets which

444
00:13:31,990 --> 00:13:29,839
are pretty much perfect

445
00:13:33,670 --> 00:13:32,000
so that's trappist-1 is probably the

446
00:13:35,030 --> 00:13:33,680
most famous of these systems but there's

447
00:13:36,790 --> 00:13:35,040
a handful of other ones

448
00:13:39,110 --> 00:13:36,800
that are really really good that we we

449
00:13:41,509 --> 00:13:39,120
should be able to get some information

450
00:13:43,189 --> 00:13:41,519
from potentially habitable worlds in the

451
00:13:45,430 --> 00:13:43,199
near-term future with either

452
00:13:48,069 --> 00:13:45,440
the james webb space telescope or

453
00:13:49,750 --> 00:13:48,079
ground-based extremely large telescopes

454
00:13:51,110 --> 00:13:49,760
now there's two ways to get the spectral

455
00:13:52,230 --> 00:13:51,120
information i talked about you need a

456
00:13:54,310 --> 00:13:52,240
big telescope

457
00:13:55,910 --> 00:13:54,320
you need a way to get spectra from the

458
00:13:58,230 --> 00:13:55,920
planet and you need to block out the

459
00:13:59,750 --> 00:13:58,240
starlight or account for the starlight

460
00:14:02,069 --> 00:13:59,760
the two methods i'm going to talk about

461
00:14:04,230 --> 00:14:02,079
real quick are transit spectroscopy

462
00:14:05,189 --> 00:14:04,240
which is what jwst will use and the

463
00:14:07,430 --> 00:14:05,199
first generation

464
00:14:09,030 --> 00:14:07,440
of the extremely large telescopes on the

465
00:14:11,350 --> 00:14:09,040
ground we'll use to analyze

466
00:14:12,550 --> 00:14:11,360
rocky exoplanets in the habitable zones

467
00:14:14,629 --> 00:14:12,560
of other stars

468
00:14:16,150 --> 00:14:14,639
now the transit technique works it gets

469
00:14:18,389 --> 00:14:16,160
the spectra from the planet

470
00:14:20,389 --> 00:14:18,399
by separating out the planet spectrum

471
00:14:22,470 --> 00:14:20,399
basically by time you you look at

472
00:14:23,750 --> 00:14:22,480
what the spectrum of the star planet

473
00:14:25,189 --> 00:14:23,760
system is

474
00:14:27,350 --> 00:14:25,199
when the planet's at different points in

475
00:14:28,870 --> 00:14:27,360
the orbit most notably when it's

476
00:14:30,470 --> 00:14:28,880
in front of or behind the star when

477
00:14:31,910 --> 00:14:30,480
you're not getting as much uh

478
00:14:33,910 --> 00:14:31,920
when it's in front of her behind the

479
00:14:34,870 --> 00:14:33,920
star compared to when the planet's on

480
00:14:36,710 --> 00:14:34,880
the side

481
00:14:38,150 --> 00:14:36,720
if you look at kind of those three cases

482
00:14:39,670 --> 00:14:38,160
in general and you can do some things

483
00:14:41,110 --> 00:14:39,680
with the full orbit that are that are

484
00:14:43,030 --> 00:14:41,120
a little bit more nuanced but if you

485
00:14:44,150 --> 00:14:43,040
look at those three cases you can

486
00:14:46,470 --> 00:14:44,160
isolate

487
00:14:48,310 --> 00:14:46,480
the the spectrum or the part the part of

488
00:14:50,230 --> 00:14:48,320
the spectrum that's being filtered

489
00:14:51,910 --> 00:14:50,240
through the planet's atmosphere and that

490
00:14:53,590 --> 00:14:51,920
lets you basically get a spectrum of the

491
00:14:55,670 --> 00:14:53,600
planet's atmosphere

492
00:14:57,350 --> 00:14:55,680
now this is best for planets around

493
00:14:59,189 --> 00:14:57,360
m-type stars which are cooler and

494
00:15:00,949 --> 00:14:59,199
smaller than sun type stars

495
00:15:03,030 --> 00:15:00,959
it's most sensitive to the upper parts

496
00:15:04,790 --> 00:15:03,040
of the planet's atmosphere

497
00:15:06,949 --> 00:15:04,800
and it's also severely impacted by

498
00:15:08,069 --> 00:15:06,959
clouds now the other technique which is

499
00:15:10,870 --> 00:15:08,079
a little bit further off

500
00:15:11,829 --> 00:15:10,880
um for the last bullet it is direct

501
00:15:13,670 --> 00:15:11,839
imaging now direct

502
00:15:16,230 --> 00:15:13,680
imaging the downside is it requires

503
00:15:17,829 --> 00:15:16,240
significant technology development

504
00:15:19,590 --> 00:15:17,839
that we haven't done yet we know how to

505
00:15:20,389 --> 00:15:19,600
do it we're investing in it we expect to

506
00:15:21,990 --> 00:15:20,399
have it

507
00:15:24,310 --> 00:15:22,000
online for the next generation

508
00:15:26,790 --> 00:15:24,320
observatories but it as of today

509
00:15:28,389 --> 00:15:26,800
it's not sufficient for the the mission

510
00:15:30,710 --> 00:15:28,399
the observatories that are using direct

511
00:15:32,710 --> 00:15:30,720
imaging or high contrast imaging

512
00:15:34,629 --> 00:15:32,720
to to get the earth-like planets and the

513
00:15:37,350 --> 00:15:34,639
habitable zones around sun-like stars

514
00:15:39,110 --> 00:15:37,360
now unlike the transit spectroscopy case

515
00:15:41,670 --> 00:15:39,120
these are better for sun-like stars

516
00:15:43,430 --> 00:15:41,680
they work worse for m-type stars and on

517
00:15:43,990 --> 00:15:43,440
and vice versa the transit technique is

518
00:15:46,069 --> 00:15:44,000
worse

519
00:15:47,110 --> 00:15:46,079
and might not even ever work for fgk

520
00:15:49,430 --> 00:15:47,120
type stars

521
00:15:50,949 --> 00:15:49,440
high contrast direct imaging also probes

522
00:15:52,949 --> 00:15:50,959
the entire atmosphere effectively

523
00:15:55,350 --> 00:15:52,959
because the light you're seeing has

524
00:15:57,350 --> 00:15:55,360
originated at the star um at least for

525
00:15:59,509 --> 00:15:57,360
the uv to near ir versions of these

526
00:16:01,509 --> 00:15:59,519
it bounces off the surface of the planet

527
00:16:03,749 --> 00:16:01,519
and passes through the atmosphere twice

528
00:16:05,189 --> 00:16:03,759
it's also less less sensitive to clouds

529
00:16:06,230 --> 00:16:05,199
for that reason clouds are always going

530
00:16:08,150 --> 00:16:06,240
to be an issue but

531
00:16:09,749 --> 00:16:08,160
they're not sort of a show stopper for

532
00:16:11,749 --> 00:16:09,759
direct imaging in the same way they can

533
00:16:13,430 --> 00:16:11,759
be for transit uh spectroscopy at least

534
00:16:14,949 --> 00:16:13,440
for near-term missions

535
00:16:16,230 --> 00:16:14,959
uh but that downside is they're further

536
00:16:17,590 --> 00:16:16,240
off because we're still developing the

537
00:16:18,389 --> 00:16:17,600
technologies to the levels they're

538
00:16:20,550 --> 00:16:18,399
needed for

539
00:16:22,069 --> 00:16:20,560
for the habitable worlds now the cool

540
00:16:23,910 --> 00:16:22,079
thing about transit spectroscopy

541
00:16:25,430 --> 00:16:23,920
that the best in my opinion is that we

542
00:16:26,550 --> 00:16:25,440
can do it sooner because the

543
00:16:28,470 --> 00:16:26,560
technologies

544
00:16:30,310 --> 00:16:28,480
uh are basically there they've been

545
00:16:32,230 --> 00:16:30,320
incorporated into a telescope

546
00:16:35,110 --> 00:16:32,240
um even though the telescope was not

547
00:16:38,069 --> 00:16:35,120
designed to do exoplanet spectroscopy of

548
00:16:39,350 --> 00:16:38,079
of rocky habitable zone worlds jwst is

549
00:16:42,069 --> 00:16:39,360
such an awesome

550
00:16:42,629 --> 00:16:42,079
piece of machinery that exists and has

551
00:16:44,949 --> 00:16:42,639
been built

552
00:16:46,870 --> 00:16:44,959
and tested and is about to launch um

553
00:16:48,470 --> 00:16:46,880
that we're going to pretty soon have

554
00:16:50,629 --> 00:16:48,480
some kind of information from these

555
00:16:54,310 --> 00:16:50,639
worlds with that transit spectroscopy

556
00:16:57,590 --> 00:16:54,320
technique um and and here's a simulation

557
00:16:59,350 --> 00:16:57,600
of both what's promising about

558
00:17:01,350 --> 00:16:59,360
that kind of observation but also what's

559
00:17:04,630 --> 00:17:01,360
perilous and challenging about them

560
00:17:06,949 --> 00:17:04,640
uh this is worked by thomas what he's

561
00:17:08,549 --> 00:17:06,959
done is he's he's made a a spectrum here

562
00:17:10,949 --> 00:17:08,559
actually two versions of

563
00:17:12,230 --> 00:17:10,959
the same planet and and a simulation of

564
00:17:14,549 --> 00:17:12,240
what jwst

565
00:17:15,429 --> 00:17:14,559
might see for that planet the first

566
00:17:18,470 --> 00:17:15,439
which i'm going to show

567
00:17:20,150 --> 00:17:18,480
in black is uh basically the spectrum

568
00:17:22,870 --> 00:17:20,160
for a planet with a clear sky

569
00:17:23,669 --> 00:17:22,880
no clouds in and you can see these peaks

570
00:17:26,230 --> 00:17:23,679
are from

571
00:17:28,549 --> 00:17:26,240
uh water or carbon dioxide absorption in

572
00:17:30,950 --> 00:17:28,559
the atmosphere and transit spectroscopy

573
00:17:31,990 --> 00:17:30,960
peaks are are what result from

574
00:17:34,870 --> 00:17:32,000
absorption

575
00:17:35,669 --> 00:17:34,880
he then adds clouds to the model and and

576
00:17:37,510 --> 00:17:35,679
any

577
00:17:39,830 --> 00:17:37,520
world that's habitable is almost certain

578
00:17:40,950 --> 00:17:39,840
to have clouds and this is the bad news

579
00:17:42,950 --> 00:17:40,960
when you add the clouds to the

580
00:17:43,990 --> 00:17:42,960
simulation you get this blue line which

581
00:17:45,430 --> 00:17:44,000
is much flatter

582
00:17:47,350 --> 00:17:45,440
you don't see all these absorption

583
00:17:48,870 --> 00:17:47,360
features from water and carbon dioxide

584
00:17:51,830 --> 00:17:48,880
like you do in the black curve

585
00:17:52,390 --> 00:17:51,840
um and it's it's pretty dim um and and

586
00:17:54,070 --> 00:17:52,400
this is

587
00:17:55,590 --> 00:17:54,080
bad because it means that we're we might

588
00:17:57,190 --> 00:17:55,600
be able to see whether or not this

589
00:17:58,549 --> 00:17:57,200
planet has an atmosphere according to

590
00:18:00,070 --> 00:17:58,559
these simulations but

591
00:18:02,070 --> 00:18:00,080
it's going to be really really hard to

592
00:18:04,230 --> 00:18:02,080
see the bio signatures themselves

593
00:18:05,830 --> 00:18:04,240
um jake lustig yeager also did similar

594
00:18:08,070 --> 00:18:05,840
calculations on what we

595
00:18:10,070 --> 00:18:08,080
you know how how many transits how much

596
00:18:11,430 --> 00:18:10,080
of jwst time would it take for the

597
00:18:12,630 --> 00:18:11,440
different trappist worlds and for

598
00:18:15,190 --> 00:18:12,640
different versions

599
00:18:16,950 --> 00:18:15,200
different model versions of those worlds

600
00:18:17,990 --> 00:18:16,960
um and and for some of them you don't

601
00:18:20,630 --> 00:18:18,000
need a lot

602
00:18:22,150 --> 00:18:20,640
um but but but this is really just to

603
00:18:23,669 --> 00:18:22,160
detect the presence of the atmosphere

604
00:18:24,310 --> 00:18:23,679
it's to know that the spectrum isn't

605
00:18:26,230 --> 00:18:24,320
flat

606
00:18:27,590 --> 00:18:26,240
uh you would need more this is just the

607
00:18:29,270 --> 00:18:27,600
number of transits you need for each of

608
00:18:30,789 --> 00:18:29,280
these permutations

609
00:18:33,830 --> 00:18:30,799
for some you only need a few and this is

610
00:18:35,430 --> 00:18:33,840
quite affordable for the one bar water

611
00:18:36,950 --> 00:18:35,440
rich atmosphere or the habitable

612
00:18:38,549 --> 00:18:36,960
atmosphere with clouds it's going to

613
00:18:39,830 --> 00:18:38,559
take dozens of spectra that's going to

614
00:18:41,909 --> 00:18:39,840
be expensive

615
00:18:43,669 --> 00:18:41,919
it's probably worth doing just because

616
00:18:46,150 --> 00:18:43,679
we're going to learn a lot there

617
00:18:47,590 --> 00:18:46,160
but this is not enough to get us the

618
00:18:49,750 --> 00:18:47,600
biosignatures themselves

619
00:18:51,590 --> 00:18:49,760
the bios signatures are going to be hard

620
00:18:53,590 --> 00:18:51,600
uh they're going to take a lot of time

621
00:18:55,190 --> 00:18:53,600
um and it's worth looking at these

622
00:18:56,549 --> 00:18:55,200
worlds and getting the spectra of these

623
00:18:58,549 --> 00:18:56,559
worlds and and we

624
00:19:00,070 --> 00:18:58,559
might find something interesting there

625
00:19:03,029 --> 00:19:00,080
but i will tell you

626
00:19:04,150 --> 00:19:03,039
my honest expectation is that we're not

627
00:19:06,549 --> 00:19:04,160
going to see

628
00:19:08,390 --> 00:19:06,559
the level of us the we're not going to

629
00:19:09,750 --> 00:19:08,400
get good enough signal to noise to to be

630
00:19:11,590 --> 00:19:09,760
able to search for or detect

631
00:19:14,630 --> 00:19:11,600
biosignatures on these worlds

632
00:19:16,789 --> 00:19:14,640
and that's not a knock on jwst in fact

633
00:19:17,669 --> 00:19:16,799
it i'm i'm impressed that it can do any

634
00:19:19,669 --> 00:19:17,679
of this at all

635
00:19:21,750 --> 00:19:19,679
without being purpose built for this

636
00:19:24,630 --> 00:19:21,760
kind of thing and this is where myself

637
00:19:26,310 --> 00:19:24,640
and the rest of the exoplanet rocky uh

638
00:19:29,430 --> 00:19:26,320
uh habitable zone

639
00:19:31,190 --> 00:19:29,440
uh community turns into aid simpson

640
00:19:33,029 --> 00:19:31,200
shaking our fist of clouds because it's

641
00:19:33,510 --> 00:19:33,039
the clouds that really are the problem

642
00:19:35,669 --> 00:19:33,520
here

643
00:19:37,590 --> 00:19:35,679
um the transit technique also has uh is

644
00:19:38,230 --> 00:19:37,600
not as good as direct imaging in many

645
00:19:40,070 --> 00:19:38,240
ways

646
00:19:41,510 --> 00:19:40,080
um but especially if you've got clouds

647
00:19:43,270 --> 00:19:41,520
just not good

648
00:19:44,549 --> 00:19:43,280
so that was kind of both how we'll

649
00:19:45,990 --> 00:19:44,559
explore but also what our current

650
00:19:48,310 --> 00:19:46,000
limitations are

651
00:19:49,830 --> 00:19:48,320
to get around those limitations i i

652
00:19:51,510 --> 00:19:49,840
think we need to go to direct imaging

653
00:19:52,950 --> 00:19:51,520
and it has those advantages i mentioned

654
00:19:54,470 --> 00:19:52,960
earlier you can look at the

655
00:19:55,990 --> 00:19:54,480
earth-like planets around the sun like

656
00:19:57,750 --> 00:19:56,000
stars you don't have

657
00:19:59,510 --> 00:19:57,760
as many issues with clouds they're not

658
00:20:01,990 --> 00:19:59,520
showstoppers um

659
00:20:03,430 --> 00:20:02,000
and we can do this for quite a large

660
00:20:04,390 --> 00:20:03,440
number of worlds as i'll get to in a

661
00:20:06,549 --> 00:20:04,400
little bit

662
00:20:08,310 --> 00:20:06,559
now we have two mission concepts for

663
00:20:09,830 --> 00:20:08,320
flagship scale observatories that would

664
00:20:11,990 --> 00:20:09,840
do this at different levels of ambition

665
00:20:14,230 --> 00:20:12,000
that's shown on the left this is lufoir

666
00:20:16,789 --> 00:20:14,240
on on the top and have x on the bottom

667
00:20:17,590 --> 00:20:16,799
this is not to scale luvoir is by design

668
00:20:20,230 --> 00:20:17,600
much bigger

669
00:20:20,950 --> 00:20:20,240
it's more ambitious than have x ex both

670
00:20:23,110 --> 00:20:20,960
missions

671
00:20:24,470 --> 00:20:23,120
though like regardless of ambition it's

672
00:20:26,230 --> 00:20:24,480
really about how many times they would

673
00:20:28,310 --> 00:20:26,240
do this kind of observation

674
00:20:30,149 --> 00:20:28,320
both missions would be able to do the

675
00:20:30,710 --> 00:20:30,159
direct imaging observation i talked

676
00:20:32,830 --> 00:20:30,720
about

677
00:20:34,230 --> 00:20:32,840
earlier the the reflected light

678
00:20:35,830 --> 00:20:34,240
spectroscopy

679
00:20:37,590 --> 00:20:35,840
and the way that works is you block out

680
00:20:39,750 --> 00:20:37,600
the star physically with some

681
00:20:41,990 --> 00:20:39,760
coronagraph or star shade

682
00:20:44,310 --> 00:20:42,000
and then the light that's left over is

683
00:20:45,990 --> 00:20:44,320
is from either the dust in the planetary

684
00:20:47,990 --> 00:20:46,000
system or from the planets

685
00:20:49,350 --> 00:20:48,000
themselves and this is what you really

686
00:20:50,870 --> 00:20:49,360
want to see you want to see a bright

687
00:20:51,830 --> 00:20:50,880
thing in the habitable zone and get a

688
00:20:54,230 --> 00:20:51,840
spectrum of it

689
00:20:55,270 --> 00:20:54,240
this is a simulation of what that image

690
00:20:57,510 --> 00:20:55,280
would look like

691
00:20:59,350 --> 00:20:57,520
using the bigger version of luvoir

692
00:21:00,630 --> 00:20:59,360
looking back at the solar system from 12

693
00:21:02,630 --> 00:21:00,640
and a half par 6 away

694
00:21:04,310 --> 00:21:02,640
you get a similar image uh with a

695
00:21:06,310 --> 00:21:04,320
smaller version of luvoir

696
00:21:08,470 --> 00:21:06,320
or or with habex if you were looking at

697
00:21:09,830 --> 00:21:08,480
it at a solar system twin that's that's

698
00:21:11,909 --> 00:21:09,840
closer to us

699
00:21:12,870 --> 00:21:11,919
than 12 and a half par 6 away so this

700
00:21:14,789 --> 00:21:12,880
image would still be

701
00:21:16,310 --> 00:21:14,799
quote unquote true um just for a

702
00:21:18,870 --> 00:21:16,320
different a different system that you'd

703
00:21:20,789 --> 00:21:18,880
be targeting

704
00:21:22,070 --> 00:21:20,799
now this is a a simulation of what the

705
00:21:23,590 --> 00:21:22,080
spectrum would look like because you

706
00:21:25,750 --> 00:21:23,600
don't just want those points of light

707
00:21:27,990 --> 00:21:25,760
you want to spread that pale blue dot

708
00:21:28,870 --> 00:21:28,000
out into its constituent colors to look

709
00:21:30,870 --> 00:21:28,880
for those

710
00:21:33,029 --> 00:21:30,880
features from the biosignature gases and

711
00:21:34,870 --> 00:21:33,039
now just think about before i had those

712
00:21:36,549 --> 00:21:34,880
just water and co2 and it was really

713
00:21:38,549 --> 00:21:36,559
flat if you included the clouds

714
00:21:41,669 --> 00:21:38,559
here's a simulation of what luvoir might

715
00:21:43,190 --> 00:21:41,679
see for a planet that's 10 parsecs away

716
00:21:45,270 --> 00:21:43,200
and you can see absorption features

717
00:21:46,310 --> 00:21:45,280
which are now down this is confusing and

718
00:21:48,789 --> 00:21:46,320
i apologize for

719
00:21:50,710 --> 00:21:48,799
for what the exoplanet community does to

720
00:21:53,430 --> 00:21:50,720
spectra and flipping their axes but

721
00:21:54,630 --> 00:21:53,440
for a direct imaging reflected light uh

722
00:21:57,110 --> 00:21:54,640
observation

723
00:21:59,669 --> 00:21:57,120
you have uh absorption associated with

724
00:22:00,870 --> 00:21:59,679
being is shown as being down on the on

725
00:22:02,310 --> 00:22:00,880
the diagram as opposed to

726
00:22:03,909 --> 00:22:02,320
up which is what i was showing before so

727
00:22:04,870 --> 00:22:03,919
that now the valleys are absorption

728
00:22:06,789 --> 00:22:04,880
features

729
00:22:08,149 --> 00:22:06,799
so for for this for this simulated

730
00:22:10,230 --> 00:22:08,159
spectrum you can see

731
00:22:12,149 --> 00:22:10,240
absorption from ozone you can see a

732
00:22:14,149 --> 00:22:12,159
broad feet i'm sorry from oxygen here a

733
00:22:15,590 --> 00:22:14,159
broad feature from ozone over here

734
00:22:17,270 --> 00:22:15,600
there's a shoulder feature here from the

735
00:22:19,110 --> 00:22:17,280
methane you can start to accumulate a

736
00:22:20,870 --> 00:22:19,120
library of gases that you know are in

737
00:22:22,549 --> 00:22:20,880
that planet's atmosphere

738
00:22:24,310 --> 00:22:22,559
and the signal to noise on the detection

739
00:22:25,750 --> 00:22:24,320
of those gases is quite good

740
00:22:27,669 --> 00:22:25,760
um and this is a simulation that

741
00:22:29,510 --> 00:22:27,679
included clouds in it so the clouds

742
00:22:31,029 --> 00:22:29,520
it impacts the the continuum but it

743
00:22:31,990 --> 00:22:31,039
doesn't impact your ability to get at

744
00:22:33,590 --> 00:22:32,000
these gases

745
00:22:35,750 --> 00:22:33,600
by the way i should mention that this is

746
00:22:37,669 --> 00:22:35,760
a simulation for luvoir but again

747
00:22:38,789 --> 00:22:37,679
havex could also do something like this

748
00:22:41,590 --> 00:22:38,799
for a different

749
00:22:42,950 --> 00:22:41,600
system that's closer up and bonus an

750
00:22:46,470 --> 00:22:42,960
awesome telescope

751
00:22:47,909 --> 00:22:46,480
out that if you can do

752
00:22:49,510 --> 00:22:47,919
if you build the observatory that's

753
00:22:50,230 --> 00:22:49,520
required to do the exoplanet direct

754
00:22:52,149 --> 00:22:50,240
imaging

755
00:22:53,830 --> 00:22:52,159
that observatory and this would also be

756
00:22:54,870 --> 00:22:53,840
true for have x would also be

757
00:22:57,590 --> 00:22:54,880
outstanding for

758
00:22:58,630 --> 00:22:57,600
remote sensing inside our solar system

759
00:23:00,390 --> 00:22:58,640
so if you're into

760
00:23:02,470 --> 00:23:00,400
a biosignature search remotely in the

761
00:23:05,110 --> 00:23:02,480
solar system levoir or habex would be

762
00:23:07,110 --> 00:23:05,120
excellent for that as well

763
00:23:08,390 --> 00:23:07,120
now for both of these we we leveraged

764
00:23:10,390 --> 00:23:08,400
the work or or

765
00:23:12,470 --> 00:23:10,400
or built off the work that jada arne and

766
00:23:14,470 --> 00:23:12,480
colleagues did on how we would detect

767
00:23:16,230 --> 00:23:14,480
not just the biosignatures from modern

768
00:23:18,149 --> 00:23:16,240
day earth but throughout earth's history

769
00:23:18,470 --> 00:23:18,159
for example archaean earth we think had

770
00:23:20,470 --> 00:23:18,480
no

771
00:23:21,510 --> 00:23:20,480
oxygen or very little oxygen in its

772
00:23:24,630 --> 00:23:21,520
atmosphere

773
00:23:26,070 --> 00:23:24,640
and no detectable ozone or oxygen

774
00:23:27,669 --> 00:23:26,080
but it had life for about a third of the

775
00:23:29,510 --> 00:23:27,679
history of life on earth

776
00:23:31,830 --> 00:23:29,520
and and we wanted to be able to detect

777
00:23:33,350 --> 00:23:31,840
that kind of world so we built luvoir

778
00:23:34,789 --> 00:23:33,360
and havoc or should say we didn't build

779
00:23:37,669 --> 00:23:34,799
it yet gosh wish we had

780
00:23:39,350 --> 00:23:37,679
we design or conceptualize luf and habex

781
00:23:41,190 --> 00:23:39,360
to be able to detect

782
00:23:43,909 --> 00:23:41,200
not just the bio signatures on our key

783
00:23:45,909 --> 00:23:43,919
and earth we're without oxygen but also

784
00:23:46,950 --> 00:23:45,919
to discriminate between an arcane

785
00:23:48,950 --> 00:23:46,960
earth-like world

786
00:23:51,269 --> 00:23:48,960
and a planet like titan that has methane

787
00:23:52,789 --> 00:23:51,279
that comes from we think non-biological

788
00:23:54,310 --> 00:23:52,799
sources

789
00:23:56,149 --> 00:23:54,320
now as we're thinking about those future

790
00:23:57,669 --> 00:23:56,159
emissions i also want us to think about

791
00:23:59,510 --> 00:23:57,679
what we need to do in the future

792
00:24:01,350 --> 00:23:59,520
for research and for the theory of

793
00:24:02,630 --> 00:24:01,360
biosignatures which is what my last few

794
00:24:04,789 --> 00:24:02,640
slides will be on

795
00:24:07,350 --> 00:24:04,799
um the first i'm going to just talk to

796
00:24:09,029 --> 00:24:07,360
jake lustig yeager's work as an example

797
00:24:10,549 --> 00:24:09,039
of us doing a more thorough

798
00:24:12,630 --> 00:24:10,559
consideration of

799
00:24:14,230 --> 00:24:12,640
surface biosignatures because basically

800
00:24:15,510 --> 00:24:14,240
everything i've been talking about as i

801
00:24:17,669 --> 00:24:15,520
alluded to earlier

802
00:24:19,669 --> 00:24:17,679
is about gaseous spout signatures now

803
00:24:20,630 --> 00:24:19,679
there is work on surface file signatures

804
00:24:22,549 --> 00:24:20,640
but i don't think

805
00:24:24,070 --> 00:24:22,559
um as broad of a community has looked at

806
00:24:24,950 --> 00:24:24,080
it especially on the the side of

807
00:24:27,350 --> 00:24:24,960
simulating

808
00:24:28,870 --> 00:24:27,360
what a luvoir or havex might see and i

809
00:24:30,710 --> 00:24:28,880
think we could do a lot more there

810
00:24:32,149 --> 00:24:30,720
um i think i think the same thing is

811
00:24:33,750 --> 00:24:32,159
true for techno signatures there's a

812
00:24:34,710 --> 00:24:33,760
couple papers just coming out the last

813
00:24:36,230 --> 00:24:34,720
few years

814
00:24:37,830 --> 00:24:36,240
on what we could do with luvoir or

815
00:24:39,110 --> 00:24:37,840
have-ex for techno signatures and i

816
00:24:40,630 --> 00:24:39,120
think we need to see more of that as

817
00:24:42,630 --> 00:24:40,640
well

818
00:24:44,310 --> 00:24:42,640
uh there's also this excellent work by

819
00:24:46,789 --> 00:24:44,320
tessa fisher which is uh

820
00:24:48,390 --> 00:24:46,799
taking us in a uh i would say it's

821
00:24:50,310 --> 00:24:48,400
quantifying our intuition

822
00:24:52,310 --> 00:24:50,320
i think there's a lot of good intuition

823
00:24:53,909 --> 00:24:52,320
and consistent intuition we've built up

824
00:24:55,990 --> 00:24:53,919
as a community of

825
00:24:57,110 --> 00:24:56,000
uh of exoplanet biosignatures

826
00:24:58,870 --> 00:24:57,120
researchers

827
00:25:00,149 --> 00:24:58,880
and and we we might all nod our heads

828
00:25:02,310 --> 00:25:00,159
and agree with each other but it'd be

829
00:25:04,870 --> 00:25:02,320
better if we had a way to quantify that

830
00:25:05,669 --> 00:25:04,880
consensus intuition and and test tessa

831
00:25:08,710 --> 00:25:05,679
fisher's work

832
00:25:10,549 --> 00:25:08,720
which which is about uh

833
00:25:12,230 --> 00:25:10,559
analyzing the complexity of the

834
00:25:13,430 --> 00:25:12,240
photochemical network in the atmosphere

835
00:25:15,669 --> 00:25:13,440
as a proxy

836
00:25:17,990 --> 00:25:15,679
for whether or not life is present there

837
00:25:19,990 --> 00:25:18,000
um is one way to do that and i think in

838
00:25:20,470 --> 00:25:20,000
an awesome way i think we need other i

839
00:25:23,350 --> 00:25:20,480
think we

840
00:25:25,190 --> 00:25:23,360
need to develop others because these

841
00:25:25,909 --> 00:25:25,200
quantified methods are really really

842
00:25:27,990 --> 00:25:25,919
important

843
00:25:29,669 --> 00:25:28,000
for for the eventual observation and our

844
00:25:31,190 --> 00:25:29,679
discussion thereof with the

845
00:25:32,789 --> 00:25:31,200
other scientists and with the general

846
00:25:34,310 --> 00:25:32,799
public

847
00:25:35,510 --> 00:25:34,320
and then the last thing so that the

848
00:25:36,230 --> 00:25:35,520
things i just mentioned are kind of at

849
00:25:37,669 --> 00:25:36,240
the top

850
00:25:39,990 --> 00:25:37,679
for the future i think we need more

851
00:25:41,830 --> 00:25:40,000
research into non-gaseous biosignatures

852
00:25:43,269 --> 00:25:41,840
um just because we've we've really

853
00:25:45,590 --> 00:25:43,279
focused on those in

854
00:25:46,870 --> 00:25:45,600
in in history the second thing is as i

855
00:25:48,630 --> 00:25:46,880
mentioned we need to quantify our

856
00:25:49,110 --> 00:25:48,640
intuition and come up with ways to do

857
00:25:50,630 --> 00:25:49,120
that

858
00:25:52,470 --> 00:25:50,640
and then the last thing is i think we

859
00:25:55,430 --> 00:25:52,480
need to look at

860
00:25:57,269 --> 00:25:55,440
earth science as and and specifically

861
00:25:57,669 --> 00:25:57,279
into climate change as a guide to how to

862
00:26:00,950 --> 00:25:57,679
be

863
00:26:03,909 --> 00:26:00,960
and i'm going to just take

864
00:26:05,190 --> 00:26:03,919
a minute here for my last slide to talk

865
00:26:06,710 --> 00:26:05,200
about that

866
00:26:09,029 --> 00:26:06,720
and this is in my opinion one of the

867
00:26:10,070 --> 00:26:09,039
most important figures or series of

868
00:26:12,470 --> 00:26:10,080
figures that that have

869
00:26:13,350 --> 00:26:12,480
has come out in the last 100 years of of

870
00:26:15,909 --> 00:26:13,360
research

871
00:26:16,789 --> 00:26:15,919
in the sciences and what this is is it's

872
00:26:18,470 --> 00:26:16,799
three plots

873
00:26:19,909 --> 00:26:18,480
one is i'm going to start with the black

874
00:26:20,950 --> 00:26:19,919
line the black line in each of these is

875
00:26:23,029 --> 00:26:20,960
for land

876
00:26:24,870 --> 00:26:23,039
ocean and land and ocean surface the

877
00:26:27,029 --> 00:26:24,880
black line is our planet's

878
00:26:28,390 --> 00:26:27,039
surface temperature history for the last

879
00:26:31,990 --> 00:26:28,400
hundred years or in the case of the

880
00:26:34,950 --> 00:26:32,000
ocean heat content for the last 50 or so

881
00:26:35,830 --> 00:26:34,960
the pink uh range is a is the range of

882
00:26:38,070 --> 00:26:35,840
model

883
00:26:39,110 --> 00:26:38,080
uh predictions of that temperature

884
00:26:40,710 --> 00:26:39,120
evolution

885
00:26:42,470 --> 00:26:40,720
which you can see is quite good and

886
00:26:44,230 --> 00:26:42,480
what's key about this pink is it

887
00:26:46,470 --> 00:26:44,240
includes everything we know

888
00:26:47,990 --> 00:26:46,480
about earth all the comp all the complex

889
00:26:50,630 --> 00:26:48,000
forcings on climate

890
00:26:53,110 --> 00:26:50,640
including the stellar variations the the

891
00:26:55,190 --> 00:26:53,120
volcanic forcings human emissions

892
00:26:57,190 --> 00:26:55,200
biological emissions that are not human

893
00:26:58,070 --> 00:26:57,200
induced everything is included in this

894
00:27:00,549 --> 00:26:58,080
pink chart

895
00:27:02,470 --> 00:27:00,559
or this this this pink line that's sort

896
00:27:03,110 --> 00:27:02,480
of the range of outcomes we get from the

897
00:27:04,710 --> 00:27:03,120
models

898
00:27:06,390 --> 00:27:04,720
and what's really good is it matches the

899
00:27:08,070 --> 00:27:06,400
temperature record really well

900
00:27:09,430 --> 00:27:08,080
well so what's up with the blue line why

901
00:27:11,669 --> 00:27:09,440
doesn't that match

902
00:27:13,909 --> 00:27:11,679
the answer to that question is that

903
00:27:15,830 --> 00:27:13,919
that's the same models where we've taken

904
00:27:18,070 --> 00:27:15,840
out the natural forcings

905
00:27:19,350 --> 00:27:18,080
and i think that's just first of all

906
00:27:21,430 --> 00:27:19,360
it's profound

907
00:27:23,029 --> 00:27:21,440
how well we can capture the increase in

908
00:27:24,470 --> 00:27:23,039
temperature over time

909
00:27:26,710 --> 00:27:24,480
when we include the anthropogenic

910
00:27:27,590 --> 00:27:26,720
forcings but how poorly we capture it

911
00:27:31,590 --> 00:27:27,600
when we don't

912
00:27:33,909 --> 00:27:31,600
that that a clean very clean a b result

913
00:27:36,549 --> 00:27:33,919
in the context of all the theory and

914
00:27:38,789 --> 00:27:36,559
complex interactions of earth's climate

915
00:27:39,590 --> 00:27:38,799
is just it's beautiful it's just a

916
00:27:41,909 --> 00:27:39,600
beautiful

917
00:27:42,630 --> 00:27:41,919
model experiment and to me it's one of

918
00:27:45,669 --> 00:27:42,640
the more

919
00:27:47,669 --> 00:27:45,679
convincing sets of evidence that climate

920
00:27:48,950 --> 00:27:47,679
change is not just real but caused by

921
00:27:50,870 --> 00:27:48,960
humans

922
00:27:52,870 --> 00:27:50,880
and i think with something that could be

923
00:27:54,789 --> 00:27:52,880
as contentious and controversial as the

924
00:27:57,990 --> 00:27:54,799
statement we are not alone

925
00:28:00,310 --> 00:27:58,000
in the context of context of something

926
00:28:02,070 --> 00:28:00,320
that is also complex because you're also

927
00:28:03,750 --> 00:28:02,080
talking about looking at one data set

928
00:28:06,470 --> 00:28:03,760
like a spectrum

929
00:28:07,510 --> 00:28:06,480
in in that results from a set of complex

930
00:28:10,149 --> 00:28:07,520
interactions between

931
00:28:11,750 --> 00:28:10,159
multiple systems at the surface of a of

932
00:28:13,269 --> 00:28:11,760
a ocean-bearing world

933
00:28:15,110 --> 00:28:13,279
and you want to know is that one

934
00:28:16,710 --> 00:28:15,120
spectrum or that's that

935
00:28:18,630 --> 00:28:16,720
that time varying spectrum whatever that

936
00:28:20,389 --> 00:28:18,640
that data set is you want to know is

937
00:28:22,950 --> 00:28:20,399
that caused by biology

938
00:28:24,149 --> 00:28:22,960
and i think like just as one of many

939
00:28:25,350 --> 00:28:24,159
examples we could take from climate

940
00:28:28,070 --> 00:28:25,360
science it would be

941
00:28:28,710 --> 00:28:28,080
super powerful if we had models like

942
00:28:31,269 --> 00:28:28,720
this

943
00:28:32,470 --> 00:28:31,279
that a captured the complexity of

944
00:28:35,510 --> 00:28:32,480
interactions

945
00:28:37,909 --> 00:28:35,520
in that habitable planet and b

946
00:28:40,630 --> 00:28:37,919
gave us sort of the ability to turn the

947
00:28:42,070 --> 00:28:40,640
biological fluxes the ecosystem fluxes

948
00:28:44,549 --> 00:28:42,080
at the global scale

949
00:28:45,430 --> 00:28:44,559
on and off so we could do this clean

950
00:28:47,029 --> 00:28:45,440
experiment

951
00:28:49,110 --> 00:28:47,039
where we say can we reproduce the data

952
00:28:50,310 --> 00:28:49,120
with biology and can we not reproduce it

953
00:28:52,950 --> 00:28:50,320
without the biology

954
00:28:53,750 --> 00:28:52,960
that kind of experiment was so critical

955
00:28:56,389 --> 00:28:53,760
to at least

956
00:28:57,350 --> 00:28:56,399
in my opinion to to our arguments and

957
00:29:00,070 --> 00:28:57,360
our understanding

958
00:29:00,789 --> 00:29:00,080
of attributing climate change to human

959
00:29:02,630 --> 00:29:00,799
activity

960
00:29:04,710 --> 00:29:02,640
and i think the same thing could be true

961
00:29:06,470 --> 00:29:04,720
if we can develop this kind of model

962
00:29:08,389 --> 00:29:06,480
for the future for for the exoplanet

963
00:29:10,870 --> 00:29:08,399
file signature search but that's just

964
00:29:11,909 --> 00:29:10,880
one example of the broader set of i

965
00:29:13,590 --> 00:29:11,919
think there's other things we could do

966
00:29:15,190 --> 00:29:13,600
with their model comparisons and

967
00:29:17,430 --> 00:29:15,200
the way that those folks use language

968
00:29:19,190 --> 00:29:17,440
and such i am well past time and

969
00:29:20,710 --> 00:29:19,200
apologies for taking up more

970
00:29:22,149 --> 00:29:20,720
of your time than i was supposed to i

971
00:29:23,909 --> 00:29:22,159
think i was supposed to come in at 25

972
00:29:25,269 --> 00:29:23,919
but i've been at 30 but i thank you so

973
00:29:26,950 --> 00:29:25,279
much for your time

974
00:29:28,630 --> 00:29:26,960
and i really appreciate it and i look

975
00:29:29,110 --> 00:29:28,640
forward to discussing this and other