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you

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[Music]

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hi everyone so what I thought was I

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thought I'd use some of the earlier

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talks and and the information and the

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pigments and the evolution of those and

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see sort of put it in a context as far

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as like the planets are concerned to see

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if we could detect these signatures

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remotely and what is what are the

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challenges in terms of wavelengths we

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would need to sort of prioritize or you

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know taking into account under the

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atmosphere and the cloud effects so I'll

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start with this

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this plot that I came across a couple of

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weeks ago which is based on the Trappist

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APIs system you know it was detected a

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couple of months ago the star being

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about 40 light years away and three

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planets happened to lie in the so-called

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habitable zone and what we see here are

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density curves from Zenit au which shows

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you know which shows what if a plant is

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made up of different kinds of materials

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like a pure water world of pure iron

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world you know where would where with

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the planets form fall in terms of

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density curves now what we see already

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here is although these are initial

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estimates recent work carried out an

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odds on this front show that the

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dat could be on the surface so I was

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curious in terms of what if we detect

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what what it was can we have can these

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planets be potentially habitable and if

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so is the case can we detect differences

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between

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purely water world and a water world

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that has some sort of biota on it be it

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you know photosynthetic organisms like

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algae for instance or and can we

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distinguish between these different

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algal communities algae are known to

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form large biological structures on

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earth and can be easily detected with

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high resolution spacecraft images and

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and they contain a diversity of pigments

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so most of the pigments that that she'll

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mentioned a nikkie mentioned in the

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earlier talks these these are very

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commonly

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then photosynthetic algae and they

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usually carry out oxygenic

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photosynthesis so you may not see

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pigments like bacteria chlorophyll which

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go out put in the infrared but you see a

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range of chlorophyll pigments and

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accessory pigments which I will come to

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in a bit so one of the things we did a

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couple of years ago and if you haven't

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come across some of this work is we sort

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of isolated a range of organisms both

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photosynthetic and non-photosynthetic

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organisms to see how the spectral

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signatures for a diversity of

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pigmentation types would look like not

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just for organisms that live in extremes

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but for organisms that encompass both

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the extreme and the niche environments

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and and these can be accessed at that

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website here it's a hosted at Cornell

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but these are hemispherical measurements

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which means that they sort of give you

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the disc integrated reflecting spectrum

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for an organism and the whole spectrum

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goes from around 0.35 micron all the way

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so what we did here was we measured

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about 137 organisms containing the range

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of pigments but I'd like to use a subset

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of those for this particular talk so I

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considered about you know about 16 to 16

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algal communities containing a diversity

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of pigmentation and what you can see

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polyphyletic in a sense that you can

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it's distinct it's challenging to put a

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particular alpha microorganism or algae

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outer organism in a particular I'll go

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band based on phylogenetic you could

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have different classes of organisms in

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the same algo algorithm division or you

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could have organisms which belong to the

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same phylogeny that belong to different

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algae so usually algae are sort of

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distinguished based on their

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pigmentation types and the the range of

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pigments that these organisms have is

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either evolution specific

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or depends on the radiation that is

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available to these organisms the other

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thing is that the absorption of these

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pigments depends on the in which

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individual pigment as well as the

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chemical environment limit in which it's

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found so you might have the same pigment

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but it might be in different chemical

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environments so the absorption shot of

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so here's a plot between reflectance and

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wavelength in the to Mike from point

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four all the way to two microns and what

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we see here is that a good example would

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be this diagram the plot in the towards

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the bottom the last three ones and all

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of them are red algae you know it looks

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green pink and red but they have the

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same pigments the difference is that

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usually for energy for instance you know

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psycrow editor in a psycho pilots

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phycocyanin these are on top of the

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chlorophyll pigments and the abundance

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of those pigments these accessory

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pigments so they help and you know they

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help in photosynthesis but they also

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help in oxidative damage prevention and

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the abundance of that will decide what

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the pig color would look like if there's

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a lot of those accessory pigments then

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the algae tend to look red in color

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where the lack of them would give you a

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greenish color then because then that

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the chlorophyll pigments show up what is

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what you also see is that most of the

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organisms look quite similar in the

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inferred near-infrared vance because

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most of them have similar what

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absorption bands which is probably due

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to the water of hydration of both in its

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free and bound States but if you go to

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the visible band then that's when you

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see differentiate differences in these

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what I'd like to do then is we took some

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of these organisms and we started we

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reused a exoplanet atmospheric code

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called eggs a prime which is a

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one-dimensional coupled radiative

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transfer code which takes into account

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the stellar and planetary of parameters

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and calculates the reflection

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transmission and emission spectrum for a

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planet the code in turn consists of a

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one-dimensional climate code

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one-dimensional for a chemistry code and

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one-dimensional radiative cap transfer

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code what we started off initially doing

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is like the previous talk that Jack

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mentioned we we covered we covered an

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entire surface with a particular

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organism to to get a sense of the

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general detectability

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and the surface signal strength so we

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know what what's the sense that its

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maximum peak and then we started

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incorporating other other surfaces so we

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tried including we play started

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exploring the parameter space for water

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then to see how these signatures would

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change if you were to have a lesser

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faction of the biota and compared to the

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water fraction that's covering in the

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ocean we also play around with the

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parameterization for clouds to see how

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clouds would help or you sort of hide

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these features from remote detection and

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so here's a plot of it looks complicated

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were to make it a little further in

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Avoyelles so basically in the infrared

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portion so if you look at 1.0 micron to

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2 microns all the features look at the

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same and these are primarily because of

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these water absorption bands and the

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atmospheric effects with our next scent

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and so it's very difficult to probe

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through the surface in these conditions

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so if I look in the visible band then

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that's when surface features start to

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sort of come up so here we have in the

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blue color like right at the bottom

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that's the complaint that's 100%

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completely covered by oceans and then I

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started playing around with the surfaces

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so I started increasing the surface

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coverage so 10

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thirty fifty seventy and hundred and you

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see that obviously four hundred you see

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more of the pigment character pigment

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absorption and the pigment properties as

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opposed to having some somewhere between

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you know some something like ten percent

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would where you have a 10 percent biota

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and a 90 percent water surface detection

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of these pigments becomes extremely

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challenging it if not impossible the

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other thing I did then was I tried to

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play around with the with a cloud

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fashion and again the same thing happens

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is before clouds sort of a have a very

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high reflectivity and clouds though

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itself have close to 90 percent

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reflective II and they try to this they

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hide all the surface atmospheric

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features and and that's what we see here

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but if I go into visible again and if I

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go from you know a completely 0 passing

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cloud coverage to a 90 percent cloud

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coverage I see that all the surface

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surface features tend to sort of

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disappear at about 60 to 70 percent

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clouds fraction so we want something

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that we need clouds we do need clouds

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because that helps in raising the signal

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so it's easy to detect because if you

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have a completely ocean world like the

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one in the blue then you're getting an

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albedo of close to 0.1 which are 0.04 in

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fact which is that which means that if

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you're looking at the planet the planet

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is going to look very very dark so

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you're not going to get any signal you

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want these photons from the planet so so

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you know these clouds will help get you

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an increase in signal but at the same

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time you don't want them to be

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overshadowing the complete atmosphere so

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so so mix somewhere between you know 40

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to 60% clouds 60% looks at the optimum

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band for these surface feature detection

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and yeah so I'll stop there by saying

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that you know surface features look a

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best detectable in the point four point

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eight micron band now with with the

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surface coverage of greater than 30

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percent in a cloud fashion of less than

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sixty percent the new future instruments

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like the GMT Seacliff which is onboard

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its respected graph on both the GMT that

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do to come on and 2024

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including other space missions like w

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first look war which probably will have

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these capabilities and for detecting

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such signatures for habitability and

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life thank you I think we have time for

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I really held her like blank Institute

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the solar system research in getting

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Germany my question I'm a bit confused

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about the aspect of cloud coverage I

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would guess that if you have more clouds

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than what you of course you get more

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photons but they wouldn't have anything

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to do with the bacteria that are below

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the clouds because they are just

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reflected stellar light so could you

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walk me through as to why your signal of

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the bacteria around the surface should

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actually increase if you have more cloud

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coverage now the cloud cover is I think

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a cloud coverage which increases because

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the clouds reflect a lot more light the

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bacteria would decrease the signal

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because the albedo the reflectance

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factor for bacteria let much lower than

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that so it'd be net integrated would be

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less than what you would have if you

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were to have this clouds by itself so

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that make sense Shawn Tomiko golden NASA

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Goddard so in theory if I'm interested

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in building a space telescope to look

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for signs of life

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would you have any advice in terms of

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not just the wavelengths but the

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spectral resolution yes we played around

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we we calculated those as well

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we tried we've been calculating the

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spectral resolution for JWST in the eye

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no JW starts in point six and it they it

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claims to have a spectral resolution of

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150 for the visible and 150 was we could

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still see significant pigment absorption

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lines in the visible bands so I would

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guess 150 is good enough as well so 150

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sufficient but but you don't know what

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the what the cutoff would be for

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detecting or not is that yes so I met

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with the MRSA days look Lopez at the CFA

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in San Francisco for the breakthrough

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meeting just this last week I was with

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Jack at fantastic and I spoke to her

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about the GMT Seacliff as well to ask

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her what the resolution for the GMT

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would be um she gave me a couple of

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white papers but this she to take this

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they still don't have the final numbers

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on that yet but that's the case I would

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be interested in looking what what the