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okay so let's talk about the

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astrobiology of karabell objects a

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little more i'll focus again on Sharon

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specifically for this talk and the

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presence of oceans and spoiler alert is

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more like past oceans not current oceans

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unfortunately but keep in mind that we

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know the Pluto sharing system really

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well now compared to two other care

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about objects but these results again

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are applicable to many other places and

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the reason why it's so interesting for

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astrobiology is that we know of about

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say a couple hundred objects you no

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larger than 200 kilometers in radius in

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the Kuiper belt and that add numbers any

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other objects to the same size in our

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solar system presumably it's the same

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thing in other solar systems as well and

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so we might be looking at the most

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common type of solid worlds in the

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universe and so if we can say something

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about the astrobiology it's pretty cool

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alright so the Pluto shirin systems it's

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about a 40 astronomical units from the

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Sun so for people who are not familiar

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with this it's pretty far so far that

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actually the surface of sharing is only

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about 40 Kelvin as Brian mentioned so so

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Sharon I'll talk more about its

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structural properties its interior its

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evolution over time and I think that's a

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good complement to the compositional

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information we just got from both to

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there and sharing so Sharon is about 600

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kilometers in radius and it has a

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density of the 1.6 grams per cubic

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centimeter and that's about between

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water or ice and rock and so we think

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it's made of a mix of water and rock

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because we have nothing better to say

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that's pretty good assumption this seems

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to be pretty common platforming

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materials now Pluto is a little bit

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denser 1.8 grams per cubic centimeters

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but it's about the same essentially so

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Pluto and turn are not alone you've

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heard that there are four extra moons in

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the system what's very interesting is

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that

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all moons and pluto and charon all

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orbits in the same plane and so rather

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than it's done that something about how

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this came to be rather than the moon is

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just being captured by the system it

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looks like the entire thing form from

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the same disk and I like a mini solar

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system right and so as Brian showed this

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is kind of the leading theory or

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hypothesis for the formation of the

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system and to get this to work you need

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to have two presenters collide and the

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progenitors are of size intermediate

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between between pluto and charon and so

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they have to strike I pretty much at the

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right speed the right angle but it works

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and so what happens is that Pluto tends

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to form from the material that was kind

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of inside like the cores of these things

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and sharing from from the outer material

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kind of the outer outer shell okay and

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whatever is left in the d'bries form of

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this moment so what's interesting here

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is that keep in mind Pluto is a little

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bit denser than insurance it's a bit

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more rock rich and that's telling us

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that you know if you deform from the

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materials that were inside this /

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generators in towards the center the

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progenitors must have been more rock

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wish here and more I switch here so in

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other words they were probably a lil bit

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differentiated between rock and ice okay

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but it's not to say that they had a

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rocky core in an icy shell like you

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expect for Europa for example because

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otherwise showing would be completely I

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see and it's not completely actually has

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some rock in it right otherwise you

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wouldn't get a density of 1.6 so we have

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to come up with a way of having the

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progenitors evolved to the point where

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they have a partial differentiation

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between ice and rock but still keep some

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rock on the outside so that was one of

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the goals of this work and we've been

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trying to understand how this

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differentiation process works so

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presumably all these objects can a form

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from a homogeneous mixture of ice and

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rock that then separates and the way to

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separate ice cream rock is just to have

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going to rock fall through the ice and

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sorted by density but to get this to

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happen you need the ice to soften

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sufficiently or even to melt

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this will usually happen at the center

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first because the center is the most

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insulated place from the frigid surface

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right then the reason why the interior

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warms usually in insight planets is

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because you have real genic elements

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that decay and the decay reaction

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produces heat and so this is what heats

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up most planets especially these guys

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who don't have tidal heating like

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europower and Solaris where are the

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moons so the center will get hot first

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the rock wall separate from ice and this

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will proceed outwards so you can get to

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intermediate situations like this where

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you have a crust of undifferentiated

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material that's too frigid to kind of

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separate work from ice or you can go all

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the way okay so perhaps the progenitor

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is going to stop here in this partial

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state and then to toe from from from

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this stuff and shine from from the crust

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and the ice there's one more layer of

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complication and it has to do with what

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the rock looks like it's pretty hard to

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tell what the rock would have been the

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de planets formed from but the best

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example we have are the most primitive

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meteorites that we have in the solar

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system least altered and these are

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contracts and contracts are made from

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these little controls which are little

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spheres of about a millimeter in size

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and they're suspended in this matrix of

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micron sized grains so it's a very

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particular grain grain size kind of kind

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of solid right so you have big grains

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and small grains if you do the math you

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find out that it the big rains settle

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much faster in water or in ice than the

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small grains with it's kind of like

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dumping a big block of a big boulder of

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rock that will go gree fast but if you

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have a little bit of silt it'll take a

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long time to settle and doing the math

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we find that the controls can settle to

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form the core but the matrix can stay

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suspended the mixed with the water and

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the ice and kind of make maybe a med

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ocean or frozen mud and so you can get

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in addition to this this axis here you

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can get a second axis where you can have

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incomplete differentiation because some

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of the rocks taste suspended in the ice

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and if you have entirely matrix grains

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potentially you have never had

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differentiation the stuff always

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kind of well mix and you can have any

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sort of intermediate cases as well all

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right so what does that tell us about

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the pretenders so the again our goal is

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to get a progenitor that that's

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partially differentiated so this is a

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plot that shows the thermal evolution so

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the temperatures inside a progenitor

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okay before Pluto and Charon form before

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the collision happens so from the

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formation until the time of collision

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which we assume takes place about a

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hundred million years after their

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formation it doesn't really matter when

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it's about a good indicative time this

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is the temperature scale here in Kelvin

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and the temperatures go from the center

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here to the surface there about a

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thousand numbers in size and so what's

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happening here is that they form pretty

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cold so you're way off to the left of

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the scale here and then because of this

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radioactive decay they heat up inside

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and at some point they reach a

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temperature threshold and here the

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threshold is the the melting point of a

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water ammonia mixture and we assume that

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they have water and ammonia and them and

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because of melting The Rock starts

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falling through the water ammonia ice

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and for Mac or we assume some fraction

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stays and finds suspended and the

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differentiation does take place all the

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way there is a crust that remains but

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with this particular model and others

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it's not very sensitive to different

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conditions you you pretty easily get

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progenitors that at the time of

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collision a partial differentiated so we

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can this way reproduce the densities of

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Pluto and Charon alright so that was one

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ball the second goal is to find out what

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happens inside Sharon afterwards during

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its history so when the collision

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happens everything is kind of reshuffled

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right Sharon comes from the outermost

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material but during the collision

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material gets pulverized and recreated

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homogeneously and so we assume Sharon

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forms homogeneous again but with a

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little less robbed and Pluto and so

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again it heats up until different shades

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into a core and Meddy mental but now

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over time the heat builds up in interior

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because the heat from the radioactive

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decay doesn't get transported outward

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this fast and so

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temperatures reach the melting point for

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the ice and so you have a notion that

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lasts about two billion years and it's

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it's quite a large ocean maybe 200

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kilometers in thickness in this model

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but again the the model is quite robust

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here in terms of varying parameters and

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so on and then it freezes the reason why

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it freezes is that at some point really

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DK just can't compete with transport

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processes so when you have a notion here

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he gets transported by convection

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instead of just conduction in the ice

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and so Sharon calls a lot faster so

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eventually ocean freezes once it freezes

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again the heat transfer becomes more

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sluggish and so it it healed heat still

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builds up a little bit enough to ream

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else part of the ocean it's a little

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colder and smaller than before but we

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have this sort of secondary ocean here

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none of this is real or not but the

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bottom line is that we can have oceans

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for several billion years inside share

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and that's that's take away okay so this

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is all models do we have any evidence

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that this could be the case and

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unfortunately I knew this was gonna

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happen because i had the keynote and i

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forgot to okay put away the animations

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okay let me show you this so i'm sharon

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remembered is this canyon here at the

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surface that that's was shown in the

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format talk and to me this Canyon is

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reminiscence of a baguette as a

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Frenchman I always think of a bread

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but but the analogy is actually quite

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good good because you get this when the

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baguette Rises or swells when you bake

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it right and so on Sharon you get this

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little Canyon here because it looks like

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it expanded upon freezing right eye

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steaks more space than water and so if

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you freezing ocean would expect Sharon

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to kind of increase in size from

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freezing and so perhaps this giant

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system of Kenyan belts at Sharon's

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equator is a sign that university you

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would have form upon freezing at the

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ocean we can talk about dates later I've

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Ryan mentioned that most of the surface

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looks older than four billion years so

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that we put it here and I'm saying it

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happens here at two billion years so

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there is an issue that needs to be

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ok and then then the second interesting

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thing you can kind of see her on the

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limb and accuse them and it looks like

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this there is this very interesting

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mountain in the modes that you guess I

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might have heard from the press release

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from the new horizons team and this has

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been the puzzle we don't see this

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anywhere else in the solar system or

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maybe almost nowhere else the closest

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analogue that my advisor Steve and I

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could think of is the Hawaiian Islands

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you can see here this little depression

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little deeper here around the island and

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the reason why that is is because when

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you have volcanism so the you know new

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rockets gets gets formed then there's a

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whole volcano here and it kind of ways

294
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on the crust and kind of flexes it down

295
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and so you can see the the flexure here

296
00:12:03,590 --> 00:12:00,970
so it kind of looks like this so could

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this could this be happening on Sharon

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again if you do the math you can find

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the minimum or did I guess the maximum

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thickness of the crest here so that

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it'll flex you know if it's paper thin

302
00:12:17,250 --> 00:12:15,970
of course it'll flex but if it's a

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hundred kilometres thick maybe it won't

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right and so you find out that if it's

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above a few kilometers it's really hard

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to flex it this way and the only way you

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can get something you know solid or not

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00:12:31,350 --> 00:12:30,010
viscous for a few kilometers is that you

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need to have a lot of heat coming under

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it because the surface is so cold here

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and the only way to get so much heat is

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to have some sort of cryo magma chamber

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so some sort of you know viscous ice or

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maybe liquid right under the surface

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that maybe erupts a little bit of

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material and flexes the crust or it just

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kind of comes under the crust and then

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it collapses over it in this sort of bit

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here so again I'm not saying this is

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happening today or that this has

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happened all over the history of Sharon

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but perhaps you know when the last bit

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of the ocean froze the the in interior

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the ice can it took more space than

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water and kind of squeeze whatever

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pockets of water were left up to the

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surface so Brad you were asking a

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question about this there how can you

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get this by squeezing water it's kind of

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a witch of shooting it up to the surface

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and kind of overcoming the negative

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buoyancy of liquid water in the ice so

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anyway just just to sum up so Sharon

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Pluto likely form when to partially

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differentiated progenitor is collided

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and we can reproduce the structure that

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matches the densities of Pluto and

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Charon the thermal mulling strongly

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suggest that churn had an ocean for a

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long time another until today but for

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civil billions of years so you know diff

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other solar systems are younger than

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ours and it's very possible that there

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are oceans in many places elsewhere even

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though now i'm sharing today and it

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looks like ocean freezing shape the

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surface so that sharon actually had an

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questions remark hey good talk mark I've

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set a question I'm not really a

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geologist but for like the Hawaiian

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island analogy those are thought to be

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formed by like mantle plumes which are

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different from like getting a volcano

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forming from a magma chamber so I don't

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know is it just is it just a issue of

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the size scale of the feature itself

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yeah I would say so so you know you when

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you talk about mental plumes versus you

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know volcanoes are rising from the

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tectonic processes and and so on someone

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who's more of a geologist then we can

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correct me if I'm wrong but essentially

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it's just telling you that the magma has

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a deep source and kind of very local

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source so that that's the case for the

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Hawaiian Islands the the magma chamber

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here you're talking about a very small

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scale thing compared to the scale of the

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plumes or the plumes would be and who

370
00:15:08,660 --> 00:15:07,019
knows if there are plumes but the source

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of the magma is hundreds of maybe

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00:15:12,350 --> 00:15:10,860
thousands of kilometers deep but the

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magma chamber here you're talking just a

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few kilometers right so it's just a

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little blip around the plume and maybe

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the the ascent is kind of stalled

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because again the water is supposed to

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sink in ice so you know it's competition

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00:15:29,569 --> 00:15:28,050
between the squeezing forces that and

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00:15:31,189 --> 00:15:29,579
the pressurization that makes the fluid

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00:15:32,930 --> 00:15:31,199
go up and the gravity that makes it go

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00:15:34,550 --> 00:15:32,940
down and so at some point you might

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00:15:35,960 --> 00:15:34,560
reach some zone of neutral buoyancy

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where he had a little bit of

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00:15:38,889 --> 00:15:37,320
accumulation I think that's what happens

386
00:15:43,819 --> 00:15:38,899
in their terrestrial volcanoes as well

387
00:15:48,439 --> 00:15:43,829
so yeah it's not incompatible yeah yes

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00:15:51,350 --> 00:15:48,449
um so how is the surface age determined

389
00:15:52,790 --> 00:15:51,360
because you know generally I think about

390
00:15:55,370 --> 00:15:52,800
surface ages being determined in terms

391
00:15:57,970 --> 00:15:55,380
of crater counting but that surface to

392
00:16:00,110 --> 00:15:57,980
me does not look saturated with craters

393
00:16:02,090 --> 00:16:00,120
so I was just wondering how they

394
00:16:04,329 --> 00:16:02,100
determine the surface age yeah this is

395
00:16:08,900 --> 00:16:04,339
an excellent question and again people

396
00:16:11,120 --> 00:16:08,910
more aware than you can can answer so

397
00:16:13,610 --> 00:16:11,130
the in the Kuiper belt it's it's pretty

398
00:16:15,769 --> 00:16:13,620
hard right the the absolute dating we

399
00:16:16,590 --> 00:16:15,779
get usually from critter counting comes

400
00:16:20,009 --> 00:16:16,600
from the your

401
00:16:22,019 --> 00:16:20,019
the moon so you know you can date

402
00:16:23,759 --> 00:16:22,029
originally some rocks from the moon you

403
00:16:26,160 --> 00:16:23,769
know how many craters are on them and so

404
00:16:27,480 --> 00:16:26,170
you have some sort of a scale it's it's

405
00:16:28,949 --> 00:16:27,490
actually really hard to extrapolate the

406
00:16:30,569 --> 00:16:28,959
scale elsewhere in the solar system and

407
00:16:32,040 --> 00:16:30,579
particularly in the Kuiper belt where

408
00:16:35,790 --> 00:16:32,050
the collisional history must have been

409
00:16:38,999 --> 00:16:35,800
so different so the the way it's been

410
00:16:41,550 --> 00:16:39,009
done it's kind of 22 with models of how

411
00:16:43,769 --> 00:16:41,560
the caravel population changed over time

412
00:16:45,360 --> 00:16:43,779
through collisions and so on and it's

413
00:16:49,319 --> 00:16:45,370
informed by the size distribution of

414
00:16:51,090 --> 00:16:49,329
care belt objects currently as they are

415
00:16:52,949 --> 00:16:51,100
observed so I'm kind of on the on the

416
00:16:55,829 --> 00:16:52,959
big end of it the ones that you can see

417
00:16:56,910 --> 00:16:55,839
and on the small end of it mostly it's

418
00:16:58,230 --> 00:16:56,920
built from what we're seeing on Twitter

419
00:16:59,910 --> 00:16:58,240
and Sharon said kinda it's kind of like

420
00:17:01,470 --> 00:16:59,920
a snake bites its tail right you can

421
00:17:05,669 --> 00:17:01,480
date widow and sure and based on what

422
00:17:08,100 --> 00:17:05,679
you see on them so and they've been

423
00:17:10,340 --> 00:17:08,110
competing models currently the the new

424
00:17:14,010 --> 00:17:10,350
horizons team has strongly converged on

425
00:17:16,490 --> 00:17:14,020
a single model that seems very plausible

426
00:17:18,480 --> 00:17:16,500
and according to this model to the

427
00:17:21,210 --> 00:17:18,490
service efficient is really old even

428
00:17:23,250 --> 00:17:21,220
though it's spiracy created just because

429
00:17:26,309 --> 00:17:23,260
it hasn't impacted that much there

430
00:17:28,260 --> 00:17:26,319
weren't that many impactors so that you

431
00:17:29,970 --> 00:17:28,270
know that's one model that everyone's

432
00:17:32,490 --> 00:17:29,980
agreeing on but who knows right it's

433
00:17:34,289 --> 00:17:32,500
it's all model dependent our results of

434
00:17:36,630 --> 00:17:34,299
a late ocean saying that the surface is

435
00:17:38,549 --> 00:17:36,640
maybe perhaps you know or at least the

436
00:17:40,710 --> 00:17:38,559
planes are two billion years old still

437
00:17:45,810 --> 00:17:40,720
for is also model dependent so it's kind

438
00:17:47,640 --> 00:17:45,820
of reaching your agreement there yeah so

439
00:17:51,930 --> 00:17:47,650
assuming New Horizons data four billion

440
00:17:54,830 --> 00:17:51,940
years is correct um I mean it is what

441
00:17:58,260 --> 00:17:54,840
you've what you found is that contradict

442
00:18:00,299 --> 00:17:58,270
new horizons I mean the if there's an

443
00:18:01,950 --> 00:18:00,309
ocean underneath for two billion till

444
00:18:04,590 --> 00:18:01,960
two billion years ago yeah doesn't

445
00:18:08,970 --> 00:18:04,600
necessarily have to show itself through

446
00:18:11,940 --> 00:18:08,980
surface features not necessarily you can

447
00:18:14,700 --> 00:18:11,950
kind of compute how much Sharon should

448
00:18:16,620 --> 00:18:14,710
have swollen you know based on how much

449
00:18:18,840 --> 00:18:16,630
ocean there was so there was an ocean

450
00:18:20,730 --> 00:18:18,850
200 kilometers deep and the density of

451
00:18:22,950 --> 00:18:20,740
water is blonde at the city of Isis

452
00:18:25,169 --> 00:18:22,960
blood and Sharon should inflate by block

453
00:18:26,399 --> 00:18:25,179
and essentially you can kind of account

454
00:18:28,110 --> 00:18:26,409
for the whole extension through the

455
00:18:29,400 --> 00:18:28,120
canyons for example but the canyons

456
00:18:32,560 --> 00:18:29,410
themselves look

457
00:18:34,480 --> 00:18:32,570
there were four billion years old so in

458
00:18:36,280 --> 00:18:34,490
this sense you know it's contrary but

459
00:18:37,660 --> 00:18:36,290
perhaps the canyons are due to something

460
00:18:40,500 --> 00:18:37,670
else and they could have in a notion