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is vesta the smallest terrestrial planet

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presented by science at nasa

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nasa's dawn spacecraft spent the last

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four years voyaging to the asteroid

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vesta and may have found a planet

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vesta was discovered over 200 years ago

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but until dawn has been seen only as an

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indistinct blur and considered little

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more than a large rocky body

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now the spacecraft's instruments are

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revealing the true complexity of this

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ancient world

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we're seeing enormous mountains valleys

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hills

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cliffs

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troughs ridges craters of all sizes and

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planes says chris russell dawn principal

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investigator from ucla

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vesta is not a simple ball of rock

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this is a world with a rich geochemical

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history it has quite a story to tell

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in fact the asteroid is so complex that

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russell and members of his team are

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calling it the smallest terrestrial

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planet

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vesta has an iron core notes russell

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and its surface features indicate that

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the asteroid is differentiated like the

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terrestrial planets earth

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mercury mars and venus

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differentiation is what happens when the

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interior of an active planet gets hot

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enough to melt separating its materials

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into layers

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the light material floats to the top and

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the heavy elements such as iron and

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nickel sink to the center of the planet

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researchers believe this process also

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happened to vesta

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the story begins about 4.57 billion

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years ago when the planets of the solar

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system started forming from the

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primordial solar nebula

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as jupiter gathered itself together its

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powerful gravity stirred up the material

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in the asteroid belt so objects there

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could no longer coalesce

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vesta was in the process of growing into

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a full-fledged planet when jupiter

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interrupted the process

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although vesta's growth was stunted it

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is still differentiated like a true

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planet

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we believe that the solar system

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received an extra slug of radioactive

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aluminum and iron from a nearby

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supernova explosion at the time when

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vesta was forming explains russell

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these materials decay and give off heat

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as the asteroid was gathering material

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up into a ball of rock it was also

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trapping the heat inside itself

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as vesta's core melted lighter material

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rose to the surface forming volcanoes

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mountains and lava flows

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we think vesta had volcanoes and flowing

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lava at one time

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although we've not yet found any ancient

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volcanoes there says russell we're still

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looking

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vesta's planes seem similar to hawaii's

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surface which is basaltic lava

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solidified after flowing onto the

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surface

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vesta has so much in common with the

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terrestrial planets

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should it be formally reclassified from

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asteroid to dwarf planet

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that's up to the international

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astronomical union but at least on the

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inside vesta has characteristics similar

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to the terrestrial planets

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if anyone asks russell he knows how he

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would vote

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