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[Music]

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thank you first I wanted to acknowledge

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my co-authors microwave David Amundsen

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who did a lot of work for this talk and

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I'm just the one up here delivering the

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talk and the background of this slide is

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what a climate modeler would like to

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believe that Proxima Centauri B would

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according to a number of people

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including people in this room Proxima

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Centauri B probably doesn't have an

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atmosphere if it has an atmosphere

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probably doesn't have water and I think

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we're going to hear another talk by

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rodrigo in a little while

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talking about the same type of thing and

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so but if you read these papers at least

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couple of them it may have water there

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are ways it could have formed farther

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out and migrated in it could have been

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formed with tons of water not lost all

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of it but formed by the hydrogen

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envelope and that burned off and left

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something reasonable behind so there are

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ways it could happen and so it's

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interesting actually as an experience to

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get up and give a talk about an

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atmosphere that may not actually exist

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but the purposes of the next 10 minutes

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let's be optimistic and imagine that it

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does exist and imagine what possible

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climates of such planet might look like

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and so climate models are optimistic in

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general there we have to be as I a model

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21st century earth climate change and if

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you if you're not an optimist about

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things it'll just drive you crazy so

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anyway other people have tried to model

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the climate of Proxima be assuming it

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has different kinds of atmospheres and

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you can change the kind of atmosphere

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and get more warming in less Grumio more

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greenhouse warming less greenhouse

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warming and so on people usually start

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with earth-like type atmospheres with

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about a bar of nitrogen with some modest

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amount of something like co2 and so on

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and so forth and here are two examples

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from the literature from much orbit at

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all use Neil and D model and from boodle

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at all using the British Met office

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model both of them making the same

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assumption

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with an aqua planet that is an ocean

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covered surface no exposed land and a

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static ocean of thermodynamics or slab

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ocean and so the ocean sits there it

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absorbs sunlight if it absorbs this

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starlight it it is liquid if it doesn't

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it turns into ice that evaporates water

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does things like that but it doesn't

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move around and so basically at the sub

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stellar point here you get liquid water

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and outside the zero degrees C Line you

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get ice alright and you can see similar

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results in both models and so for this

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type of planet what happens at the sub

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stellar point stays at the sub stellar

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point and rapier Homburg called that

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configuration eyeball earth alright and

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that's sort of the the the typical way

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that people who use 3d models try to

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simulate exoplanets because it's the

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quickest way of doing those calculations

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but oceans are a lot more interesting

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than that they do other things but

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actually matter to the climate so oceans

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have thermal inertia and depending on

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how deep you assume the ocean is it can

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have a lot of thermal inertia which

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really slows down the response of the

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climate to a change in installation

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alright

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oceans transport heat in GCMs without a

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dynamic ocean the atmosphere atmosphere

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transport seep of the ocean does not

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oceans transport heat and make it a lot

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easier to keep things warmer over a

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larger region of the atmosphere but they

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take heat away from the sub stellar

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region as we'll see in a minute and keep

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things cooler there and that was

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demonstrated in the paper by WHO and

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yang 2014 who uses dynamic ocean to

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simulate a generic planet orbiting an M

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star and then another point that hasn't

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been emphasized very much in this one

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paper by Colin at all is that oceans

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have salt in them and salinity depresses

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the freezing point that's a good thing

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if you're trying to make habitable

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planet people do a lot of

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experimentation with composition of the

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atmosphere they don't do much

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experimentation for composition of the

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ocean so let's look at a couple of those

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things so we're doing our simulations

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with a different 3d general circulation

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model called Rocky

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Reidy that's developed at NASA Goddard

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Institute for Space Studies as an

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outgrowth of our terrestrial climate

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model and that model is described in a

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paper oops so I'm going away how do I go

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back let's see there we go it's

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described in a paper by microwave all

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that's been posted on the archive and

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it's under review and app.js supplement

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series it's four by five degree model

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with 40 layers in the atmospheres we're

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using a 900 meter deep ocean with nine

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layers assuming an actual planet like

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the previous studies we're doing runs

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with synchronous rotation but we're also

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doing runs with three two spin orbit

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orbit resonance one with zero

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eccentricity and learn with 0.3

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eccentricity which is close to the upper

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limit that people think is reasonable

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we're using sort of typical fo earth

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type atmosphere for today's top but

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we're trying other compositions and

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we're using an ocean with different

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salinities something typical of the

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earth something that's fresh water and

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something that's more like the Dead Sea

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and so here are examples of what you get

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with such a model on the left just as a

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sanity check we ran our model first with

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a thermodynamic ocean that the previous

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modeling papers use just to show you

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that we can get the same result for that

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type of simulation I bowler but now here

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is the result for the ocean the dynamic

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ocean and it looks very much actually

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like what whoo and Yanks on their 2014

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paper what happens that in response to

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the heating at the sub stellar point

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over here you get these atmospheric

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waves Rossby waves on either side of the

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of the equator upstream of the sub

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stellar point and then you get a Kelvin

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way downstream creates this unusual

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pattern of above freezing temperatures

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and I should but say by the way that I'm

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using a color bar convention in which

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the transition from blue to yellow is

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the transition from below to above

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freezing not below to above zero degrees

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C because it's different with salt so

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anything this yellow is is liquid water

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and this was called Baku and yang

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Lobster Earth instead of eyeball earth

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and you go from a planet that has only

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20% open ocean without the dynamic ocean

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into something has open more than twice

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the open ocean even though the maximum

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temperature the substellar point is a

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lot cooler than it is with the

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thermodynamic ocean still this barely

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above freezing seemingly water is

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covering a fairly large fraction in the

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planet okay something else people worry

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about for habitability is the transition

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to a moist greenhouse especially around

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m-step planets around M stars where

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there's lots of shortwave absorption by

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water vapor that can wind up putting

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lots of water vapor into the

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stratosphere and get you to an on

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habitable climate sooner than you like

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and that's a concern for n star M stars

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this is a figure from a paper that we

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have in review by Yuka Fuji in app j

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showing how the stratosphere water vapor

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changes with total incident flux for

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four different kinds of stars here this

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is the same thing plotted versus surface

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temperature substellar point and this is

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the same thing plotted versus the near

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IR flux which is actually the

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fundamental parameter for stratospheric

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water vapor

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just to show you Proxima B just gets too

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little installation it's nowhere near

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this place up here where you start to

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worry about moist greenhouses so

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whatever else may be bad about Proxima

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be moist greenhouse is not one of them

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given how little installation it

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receives okay onto more exotic types of

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oceans on the Left we've shown the

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result with the experiment which we've

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used a fresh water ocean zero salinity

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and on the right we've used this dead

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sea salinity of two hundred and sixty

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practical salinity units that's grams

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per kilogram well talk about the

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freshwater case first you can see

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compared to the nominal Lobster earth

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pattern the pattern is still there but

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it's a lot smaller this is kind of a

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baby lobster the reason the reason is

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that in the ocean you have two different

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kinds of heat transport you have a

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wind-driven heat transport that's

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usually in the upper layers and then you

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have a density driven or thermohaline

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circulation in which the density

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differences that drive it are due to

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temperature differences and salinity

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differences you take away the salt and

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you only have the temperature component

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so you weaken thermohaline circulation

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you can't transport as

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and then there's the peculiar feature of

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fresh water that its density peaks at

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four degrees C which is not the case for

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salty water and so as you move away from

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the substellar point and move towards

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zero you actually get to this four

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degrees C contour and all the water

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starts to sink around the edges there

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and it's not available actually to

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transport the near near surface water

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around to the Nightside so you get a

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very confined region of of open oceans

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only 32% but you go to very high

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salinity and pun intended

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take the simulation with a grain of salt

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these this ocean model was not intended

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to go up to things like 260 PSU but the

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one thing that you probably can't count

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on is that the freezing point is very

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very depressed at 260 PSU it's down

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there minded but it's about it and at

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the eutectic point it's about

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closed-toed minus 21 degrees or

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something like that and so you wind up

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having a planet that is not above 0

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degrees C anywhere on the planet yet 97%

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of the planet is liquid water ok and so

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you don't have to build up bars of co2

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to make a planet that is technically

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habitable in its ability to sustain

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surface liquid water you can make

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something that looks completely cold but

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still could be habitable with the price

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you pay that it's really really salty ok

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is a really really salty ocean

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conceivable well maybe I don't really

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actually know that much about that but

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people who study Europa there's a paper

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from Han and Chava where these Galileo

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magnetometer data to try to figure out

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how saline Europa's subsurface ocean may

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be and in the end they kind of came to

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the conclusion by the way Europa they

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think is not sodium chloride dominated

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ocean they think it's a magnesium

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sulfate epsom salts dominated ocean but

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they came to the conclusion that the

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Galileo magnetometer results are

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actually most consistent with a salinity

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of that ocean that's very close to

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saturation for magnesium sulfate and so

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the idea of a really really salty ocean

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we may actually even have an example

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right in our own solar system who knows

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could anything live in an ocean that

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salty and that cold well it's amazing

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the paper by McKittrick at all 2012 and

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they found this hello file

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planta caucus hello cryo Phyllis or 1 in

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Arctic permafrost and they run it back

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to the lab and got it to grow and divide

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at minus 15 degrees C at 180 practical

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salinity units so you know not bad Vic

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yeah life will find a way it's amazing

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right so the other thing that we did is

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to try to simulate Proxima Centauri B

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now not in synchronous rotation but in

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three two spin orbit resonance you get a

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very different situation depending on

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whether you assume there's any

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eccentricity or not without any

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eccentricity this is the pattern of

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incident stellar radiation without any

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eccentricity then you get an even a

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climatologically even there's a diurnal

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cycle of course because it's not in

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synchronous rotation but you get a

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climatologically even pattern of

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installation at all longitudes but if

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you add eccentricity this is the point

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three case then you don't because then

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basically every time you come around

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again

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a different side of the planet is

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spacing the star and so you get two

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preferred longitudes of high

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installation with weaker installation

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between so if you do if you apply this

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type of installation pattern to a

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thermodynamic ocean like the ones I

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showed you earlier then you don't get an

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eyeball or if you get a to eyeball earth

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is basically what you get with ice in

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between this is the sea ice cover that

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we get from the model with a dynamic

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ocean with this version of the

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installation there's just not there's

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you melt the planet on the day side in

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the equatorial region but it freezes up

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again on the night side so you get kind

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of climatologically partial sea ice

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cover in a small band near the equator

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and ice everyplace else no place that's

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completely ice-free but with this

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pattern where you're actually getting

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fairly intense installation in two

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places on the globe then you get open

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ocean and because the ocean transports

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heat because the ocean has a lot of

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thermal inertia so that it doesn't

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automatically freeze over once the

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planet moves over onto the night side

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you actually get a permanent

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what would people people would call a

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water belt of liquid water all around

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the planet so that's a fairly habitable

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looking planet and that's what normal

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earth type salinity okay so to conclude

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dynamic ocean implies that you might

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have a much colder but a broader

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habitable region then a static ocean

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would imply if you have a synchronously

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rotating planet with an earth-like

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atmosphere if you have a highly saline

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ocean you have this possibility of an

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almost completely liquid covered planet

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that nonetheless stays below zero

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degrees C everywhere on the planet and

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we have examples on earth of critters

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that actually grow in conditions like

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that amazingly if you have a planet in

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three to spin-orbit residence then with

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eccentricity you can produce a nice

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habitable belt of water around the

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equator and of course all of this is on

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the condition that Proxima B has an

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atmosphere and then it has water which

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00:14:32,610 --> 00:14:31,150
it probably doesn't but maybe let's be

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optimistic thank

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00:14:41,480 --> 00:14:38,960
[Applause]

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all right so we're about three minutes

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ahead of schedule so we have time for

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maybe a few quick questions so this is

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with an earth-like atmosphere but what

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00:14:56,420 --> 00:14:53,910
happens if you increase the co2 maybe

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four five times or even more than that

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so so we're doing runs right now with an

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hour key and earth type atmosphere we're

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specifically doing runs with non

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atmosphere like what char net all looked

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at in their 2013 paper their case a

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which as I guess about point nine

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00:15:20,620 --> 00:15:16,140
millibars of co2 point nine millibars of

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00:15:23,750 --> 00:15:20,630
methane as well and you get a broader

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00:15:26,360 --> 00:15:23,760
region of open ocean water but not a

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00:15:27,650 --> 00:15:26,370
completely open ocean region for that if

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00:15:29,510 --> 00:15:27,660
you go up to very high co2

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00:15:31,850 --> 00:15:29,520
concentrations we have not done that

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00:15:34,580 --> 00:15:31,860
experiment yet but tibetan all did that

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00:15:37,040 --> 00:15:34,590
experiment with a one-bar co2 atmosphere

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00:15:41,740 --> 00:15:37,050
for one-bar co2 atmosphere you can make

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00:15:45,230 --> 00:15:43,730
another question about parameter

388
00:15:46,880 --> 00:15:45,240
sensitivity what happens if you change

389
00:15:50,150 --> 00:15:46,890
the rotation rate does the mat-su know

390
00:15:52,730 --> 00:15:50,160
gill pattern changes well or so so yeah

391
00:15:55,460 --> 00:15:52,740
so it the the details of it will change

392
00:15:59,060 --> 00:15:55,470
you'll still get the same basic pattern

393
00:16:01,220 --> 00:15:59,070
and I can tell you that for a fact that

394
00:16:02,450 --> 00:16:01,230
it changes the shape a little bit of the

395
00:16:03,770 --> 00:16:02,460
pattern but doesn't change the pattern

396
00:16:05,780 --> 00:16:03,780
because the first time we ran these

397
00:16:06,980 --> 00:16:05,790
experiments we mistakenly having the

398
00:16:09,260 --> 00:16:06,990
mistake in the code that gave us a

399
00:16:12,170 --> 00:16:09,270
rotation rate that was that was twice as

400
00:16:13,880 --> 00:16:12,180
slow as the actual rotation rate so

401
00:16:15,410 --> 00:16:13,890
changes the look of the pattern a little

402
00:16:18,500 --> 00:16:15,420
bit but the mat-su Nabeel pattern is

403
00:16:21,830 --> 00:16:18,510
still there all right make your last

404
00:16:23,270 --> 00:16:21,840
question quick okay I'll hold off on

405
00:16:25,250 --> 00:16:23,280
some of the comments that I had just a

406
00:16:27,560 --> 00:16:25,260
quick couple comments about two oceans

407
00:16:29,330 --> 00:16:27,570
in our own solar system i Jerry's still

408
00:16:32,030 --> 00:16:29,340
out about whether your opposition's

409
00:16:33,560 --> 00:16:32,040
magazine sulfate or sodium chloride in

410
00:16:35,030 --> 00:16:33,570
hand provided a lower bound the other

411
00:16:36,650 --> 00:16:35,040
thing is that if you're looking for a

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00:16:39,740 --> 00:16:36,660
saturated ocean Callisto might be a good