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>>NARRATOR: It turns out that
Ceres, the first and largest

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asteroid discovered in the main
asteroid belt, surprisingly has

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been geologically active within
the past billion years.

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[music]

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NASA’s Dawn spacecraft
arrived at dwarf

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planet Ceres in March, 2015.  
>>OTTAVIANO: We were expecting

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an inert rocky body. >>LUCY: We
expected Ceres to be a

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cold rock. >>NARRATOR: One
intriguing feature Dawn

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discovered on the surface of
Ceres is an enormous, lone

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mountain the team named Ahuna
Mons.   >>OTTAVIANO: We have

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been looking in detail about the
shape of the mountain.

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>>LUCY: It was very tall
and had steep slopes.
And that reminded us of

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certain places in the solar
system, including Earth and

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Mars, that had domes that were
formed by volcanic activity.

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>>OTTAVIANO: And
we have found that Ahuna
Mons’ shape is very

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similar to that of a volcanic
dome. >>NARRATOR: Along with the

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shape of the dome, the facts are
that there is no evidence of

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another formation mechanism such
as an impact crater, and the

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surface features on the summit
and sides of the mountain look

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incredibly similar to known
volcanic domes. This all

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provides substantial evidence
that Ahuna Mons is in fact of

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volcanic origin. Volcanoes on
earth are fueled by magma

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composed of molten rock.  But
Ceres is far too cold to melt

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silicate rock in its interior.
>>LUCY: We then concluded that

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the magma had to be composed of
mostly very salty water, and
when

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exposed to the surface, they
would freeze and form this

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steep-sided dome. >>NARRATOR: A
volcano made of water or other

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ices instead of rock is called a
cryovolcano.  Scientists have

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detected evidence of
cryovolcanic activity before -

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plumes from Saturn’s moon
Enceladus and Neptune’s moon

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Triton and volcanic-looking
mountain ranges on Saturn’s moon

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Titan.  The salty muddy
mountain Ahuna Mons is yet

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another new form of cryovolcanic
activity discovered.

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>>LUCY: There’s no other place
in the solar system that has a

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structure like Ahuna Mons, and
it has to be formed by

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cryovolcanic activity.
>>NARRATOR: Moons around gas

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giants can heat up from the
frictions of interactingtheir

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orbits, but the isolated dwarf
planet Ceres is so small and

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cold that we wouldn’t have
thought it could have liquid

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water in its recent past.
 Evidence suggests, however,

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that Ahuna Mons is a relatively
young feature.

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>>OTTAVIANO: First of all,
the surface is very bright,
and as surfaces get

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darker with time, it’s
brightness tells us it’s a young

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feature. And second, we see very
crisp morphologies, very sharp

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features, and this also tells us
it’s young, as the features get

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muted and smooth with time. And
third, we have been looking at

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crater density and we see very
low density of craters. And this

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tells us that Ahuna Mons was
formed within the last billion

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years of Ceres’ history. Ahuna
Mons is evidence that Ceres was

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active in the recent past and
might still be active today.

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>>LUCY: That tells us that there
has to be something beneath the

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surface of Ceres near Ahuna Mons
that heated the material to the

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melting point and made it push
through the cracks on the

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surface. >>NARRATOR: The source
of this heat is still an

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intriguing mystery that
planetary scientists are anxious
to solve.  

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[beep beep, beep beep...]
[music fades out]