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[Music]

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i'm brian holler

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i am a starting my fifth year grad

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school

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here at the university of colorado in

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the aps department so

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astronomy and or astrophysics and

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planetary science i work with leslie

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young at the southwest research

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institute

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she's a deputy project scientist on new

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horizons um i will not be presenting new

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horizons data i'm not on the mission

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i'll be presenting

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um ground-based observations of sharon

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uh which are pretty hard to come by um

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and this picture is a combination of

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pluto and sharon

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yin yang pattern

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showing that they're you know two sides

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of the same

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thing

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they're very different but uh

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so a little overview of what i'll be

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talking about

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sharon is the largest moon of pluto but

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they have very different surface

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compositions sharon is uh primarily

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covered in water ice in both crystalline

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and amorphous

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phase

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as well as ammonia hydrate

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pluto is covered in relatively volatile

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ices

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molecular nitrogen

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methane and carbon monoxide

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and it took the new horizons mission to

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actually detect water on the surface

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it's never been detected in ground-based

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spectra on pluto

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it's one of only two objects in the

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kuiper belt

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uh where ammonia has been detected the

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the high crystalline water ice fraction

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is kind of strange

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on charon

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we'd expect so crystalline water ice is

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the kind of ice that you find on earth

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primarily you know in your ice cube it's

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well ordered crystalline matrix

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uh when it interacts with radiation or

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cosmic rays uh those bonds break and you

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get an amorphous solid sort of like

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glass

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where there's randomly oriented

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molecules in the solid

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so you expect over time you lose the

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crystalline water ice you gain more

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amorphous water ice

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that doesn't appear to be the case on

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cheron

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we also you know because we detect

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ammonia on the surface

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as well as crystalline water ace has

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been put forward that there's some sort

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of

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um

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resurfacing mechanism such as

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cryovolcanism going on on cheron

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now i'm here to tell you that i think we

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don't need cryovolcanism

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it can be explained

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uh

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other ways um so sharon

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is not active and i apologize to mark

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who's going in two talks from now

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based on his talk title it seems like

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he's going to be talking about how

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so sharon and pluto

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giant impact say a proto pluto proto

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cheron

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you have a grazing collision that

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results in

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the formation of the system we see today

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which has five moons four of them are

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tiny likely formed from a debris disk of

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ice

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after the formation of the other two

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objects

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but after this point in time they have

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followed very different evolutionary

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paths

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even though they share the same orbit

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same radiation environment

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they have very different surface

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compositions very different histories

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so when i was looking at all the talks

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uh i saw people were probably going to

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talk about how they went to really cool

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places so i felt like i needed to

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represent the observational astronomers

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i went to hawaii last year for 50 days

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to get all this data

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to obtain this data

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and

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one of the nights i was there

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and that was the date of the closest

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approach of new horizons to pluto

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uh the image up there

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was the data that i was taking at the

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exact moment of the flyby

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the rotation period of charon is in

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pluto about 6.4 days so the four hour

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time difference or you know the light

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travel time didn't really make much of a

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difference so we were observing the same

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hemisphere pluto the new horizons was

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um

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so that that's something i'm

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very proud of that i was able to do

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because i wasn't on the mission

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so the data that i got uh are spectral

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data cubes so i like to think of them as

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a loaf of bread

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so if you take a slice out of a loaf of

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bread

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you have you know 2d slice

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and that slice corresponds to a

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particular wavelength so if you look at

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the bread loaf long ways you're looking

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you get an image but if you look at it

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sideways you get a spectrum

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so we had six nights uh between the 14th

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of july and 30th

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30th of august all at different center

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on different sub-observer longitudes so

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you're looking at different parts of

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sharon's surface

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during each

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night

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and we did we obtained these in the near

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infrared

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using adaptive adaptive optics and as

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you can see here pluto and charon are

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fully separated pluto is the bright one

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on the bottom

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sharon is the denver one on the top

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this is hard to do because they're

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separated by less than an arc second

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so hasn't been done too much before

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and here is what you've all been waiting

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for squiggly lines

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so this shows the this is the average

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spectrum of cheron it's still a little

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ratty because sharon is so

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faint

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we see signatures of

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amorphous

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water ice crystalline water ice

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and ammonia hydrate

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darkening agent that nobody's been able

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to effectively model

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at any point in time

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we have no idea what that is

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um this feature here

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1.65 micron band of is unique to

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crystalline water ice it does not show

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so what i did was i i fit

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i fit gaussians to

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this band and to this band to determine

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properties of of the species on the

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surface

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in particular the 1.65 micron band is

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temperature dependent

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so it depends on

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so the the central wavelength of the

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band depends on temperature

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so you can use that as a gauge of what

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the surface temperature is

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and for the ammonia hydrate wanted to

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figure out

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particularly the integrated band area

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which is a sort of like an equivalent

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width and gives you the amount of the

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stuff on the surface that's what it's

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related to

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so

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um and then use the six nights that we

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have to determine longitudinal

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variability yeah how does this stuff

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vary across the surface

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there's some limitations to this

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uh

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in particular you're adding a lot of

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noise when you're doing

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when you're trying to you know get the

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spectrum from the data cube

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you're adding way more pixels in each

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image than you would if you're doing

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long slit so you're making it noisier

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however because of the small separations

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this is one of the only ways to do this

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from the ground to get a separate share

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and the the temperature calculation is

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not very precise uh however we do end up

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other values determined previously

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so here's some results

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they're not terribly exciting because of

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this this noise the lower signal to

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noise

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we're looking at temperature as a

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function of longitude

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the red solid line is the average

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surface temperature

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so that's 41 kelvin

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and we the dashed lines show the

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uncertainty

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all of the values

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are consistent with the average value

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and with each other

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so

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no difference in surface temperature

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this is important for you know

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determining an active cipher

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cryovolcanism possibly you expect a

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warmer part of the surface for where

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cryovolcanism is currently

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currently going

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on and here's some plots for the ammonia

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hydrate band

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we see a similar thing there's no

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difference in the amount of ammonia

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hydrate across the surface of cheron

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within our ear bars

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and i point to

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with this big arrow to the one down here

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which is the band area which gives you

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the amount of ammonia hydrate on the

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surface

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appears to be constant

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and i'll point out something although it

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may not be statistically significant

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and this shape

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so if that ended up being real that

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would be pretty interesting um

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we need to

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find a way to beat down the noise

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so

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from new horizons the youngest surface

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feat the youngest surface age

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is four billion years

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so the la the the i mean anything

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everything is older than 4 billion years

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based on laboratory data you can get

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crystalline and amorphous water ice

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reaching an equilibrium over time this

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happens on the order of you know even

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half a billion years

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after the ice has been placed on the

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surface

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so even though your the radiation is

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coming in destroying the crystalline

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water ice it's thermally recrystallizing

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based on temperature so even for

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temperatures of 30 kelvin

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you get this in less than a billion

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years

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and the temperature

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determines how much crystalline water

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it's possible that ammonia is diffusing

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through the surface ice to remain on the

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surface because it should be destroyed

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so there is a replenishment process for

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that but it's likely diffusion and if

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you know

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if this

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similar shape for these

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is real

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uh

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that would mean that you know areas

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where it's warmer

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you're getting more ammonia which means

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you know you have faster diffusion rates

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so

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applying this the rest of the kuiper

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belt

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crystalline water ice has been detected

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on a bunch of other bodies

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including haumea

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kwawar and orcas as well as haumea's

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moons the maka and hayaka

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00:10:58,150 --> 00:10:55,279
and the haumea collisional family

293
00:11:01,110 --> 00:10:58,160
some of these objects are extremely tiny

294
00:11:02,630 --> 00:11:01,120
maybe 170 kilometers across

295
00:11:04,630 --> 00:11:02,640
you would not expect to research you

296
00:11:06,630 --> 00:11:04,640
know cryovolcanism resurfacing to go on

297
00:11:08,069 --> 00:11:06,640
on a tiny object like that

298
00:11:09,829 --> 00:11:08,079
um

299
00:11:12,389 --> 00:11:09,839
and orcis is the only other object where

300
00:11:14,069 --> 00:11:12,399
ammonia has been detected

301
00:11:14,949 --> 00:11:14,079
you know so we can apply what we've

302
00:11:17,750 --> 00:11:14,959
learned

303
00:11:19,190 --> 00:11:17,760
from about cheron with new horizons

304
00:11:20,550 --> 00:11:19,200
these other objects that we probably

305
00:11:23,269 --> 00:11:20,560
will never go to

306
00:11:25,430 --> 00:11:23,279
and say that you know cryovolcanism

307
00:11:27,430 --> 00:11:25,440
or other replenishment processes are not

308
00:11:32,069 --> 00:11:27,440
required to explain the surface

309
00:11:38,389 --> 00:11:33,590
so

310
00:11:39,829 --> 00:11:38,399
radiogenic heating should be pretty low

311
00:11:42,310 --> 00:11:39,839
for cheron

312
00:11:44,150 --> 00:11:42,320
and tidal heating should be negligible

313
00:11:45,350 --> 00:11:44,160
because it has a nearly circular orbit

314
00:11:48,470 --> 00:11:45,360
around pluto

315
00:11:51,670 --> 00:11:48,480
so you have no possibility of an energy

316
00:11:54,150 --> 00:11:51,680
source likely no ocean

317
00:11:56,949 --> 00:11:54,160
or liquid water under the surface so no

318
00:11:59,110 --> 00:11:56,959
life as we know it um pluto however

319
00:12:01,110 --> 00:11:59,120
could be a different story and i provide

320
00:12:04,470 --> 00:12:01,120
a segway

321
00:12:07,829 --> 00:12:06,069
if you don't like the pun

322
00:12:11,030 --> 00:12:07,839
if you don't like it i can meet you

323
00:12:12,949 --> 00:12:11,040
outside later

324
00:12:15,170 --> 00:12:12,959
so i'll leave you with a haiku

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00:12:23,690 --> 00:12:15,180
and take any questions

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00:12:27,509 --> 00:12:23,700
[Applause]

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00:12:30,069 --> 00:12:27,519
[Laughter]

328
00:12:31,430 --> 00:12:30,079
so i i actually agree with you um i

329
00:12:33,110 --> 00:12:31,440
think it's unlikely that sharon has a

330
00:12:34,470 --> 00:12:33,120
notion today and that he has quiet

331
00:12:35,750 --> 00:12:34,480
volcanism today and

332
00:12:36,790 --> 00:12:35,760
you guys will see

333
00:12:38,550 --> 00:12:36,800
um

334
00:12:40,150 --> 00:12:38,560
just a comment about the difference

335
00:12:42,550 --> 00:12:40,160
between pluto and sharon and i guess

336
00:12:43,350 --> 00:12:42,560
it's slow for the next speaker as well

337
00:12:45,910 --> 00:12:43,360
um

338
00:12:47,750 --> 00:12:45,920
isn't the the reason why their surface

339
00:12:49,590 --> 00:12:47,760
and uh the the fact that pluto has an

340
00:12:51,509 --> 00:12:49,600
atmosphere um

341
00:12:53,910 --> 00:12:51,519
isn't the reason for the dichotomy

342
00:12:55,509 --> 00:12:53,920
uh simply that sharon has a lower

343
00:12:57,350 --> 00:12:55,519
gravity and so it doesn't hold on to any

344
00:12:59,590 --> 00:12:57,360
guesses that would come out of it yep

345
00:13:02,150 --> 00:12:59,600
that's the that's the explanation

346
00:13:04,150 --> 00:13:02,160
it's pretty simple

347
00:13:06,389 --> 00:13:04,160
but you know they start in the same spot

348
00:13:08,230 --> 00:13:06,399
and this is important for you know

349
00:13:10,710 --> 00:13:08,240
detecting things such as non-methane

350
00:13:12,069 --> 00:13:10,720
hydrocarbons potentially on charon at

351
00:13:14,389 --> 00:13:12,079
some point in the past it might have had

352
00:13:15,990 --> 00:13:14,399
these volatile ices but they were lost

353
00:13:17,190 --> 00:13:16,000
and during that time you can get you

354
00:13:19,509 --> 00:13:17,200
know ethane

355
00:13:23,910 --> 00:13:19,519
ethylene acetylene on the surface

356
00:13:23,920 --> 00:13:27,269
other questions