WEBVTT FILE

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Maven is a spacecraft at Mars
that's part of the Mars Scout program,

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Maven's primary objective is to understand

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the evolution of the
upper atmosphere of Mars.

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We know that liquid water once
existed on Mars — oceans,

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and lakes, and rivers of water.

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But where that water went
has been a mystery.

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For water to exist in stable liquid form,

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you need to have enough
atmospheric pressure.

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So, what happened early on in Mars'
history is the atmosphere started

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getting eroded away, namely
by processes and drivers from the Sun.

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That atmospheric pressure
got lighter and lighter,

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and then the water started evaporating,
and some of it was trapped

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in the surface, and then
a lot of it escaped to space.

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There are many ways
that the atmosphere can escape,

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but the one I've been focusing on

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for the last ten years
is called sputtering.

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Sputtering is like doing
a cannonball in a pool.

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The cannonball would be
the heavy ions coming in

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really fast into the atmosphere,
and as they hit the atmosphere,

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they splash particles out.

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When Maven first arrived at Mars,

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we thought we would see
sputtering immediately,

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but it's an exceptionally elusive
escape process to observe.

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We've had hints that this process exists

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and is operating at Mars
through things like isotope ratios.

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Argon has different isotopes,

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some of them are lighter
and some of them are heavier.

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What Maven found was that the lighter

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isotopes are preferentially removed
in the atmosphere.

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This is incredibly hard to do,
and no other

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atmospheric escape process
could explain a ratio like this.

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Think of it like stumbling upon ashes

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in a fire pit the morning
after a campfire.

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Now, you haven't
actually seen the fire yet,

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but you're pretty
sure it existed.

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In 2017, Maven
found something like this,

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the ashes being isotope ratios.

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These isotope ratios gave us a hint
that sputtering must exist.

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So, in this result, sputtering is the fire.

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What we saw
was Argon at high altitudes

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correlated with the electric fields
driven by the solar wind.

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We had to have observations
from three instruments simultaneously.

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We needed to measure
the solar wind from SWIA,

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we needed to measure the magnetic
fields from our magnetometer,

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and then we needed
to measure Argon with NGIMS.

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It took ten years of data
to finally find the statistics

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and have enough data from each of

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those three instruments to be able
to put this result together.

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[ NASA MEATBALL ]