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Saturday, December 31, 2011

The Mountains of Vesta

Timothy Birdnow

Nasa'S Dawn spacecraft has found an enormous mountain on the asteroid Vesta - and big chunks of that very mountain are found all over the Earth!

From Nasa Science:

Dec. 30, 2011: When NASA's Dawn spacecraft entered orbit around giant asteroid Vesta in July, scientists fully expected the probe to reveal some surprising sights. But no one expected a 13-mile high mountain, two and a half times higher than Mount Everest, to be one of them.

The existence of this towering peak could solve a longstanding mystery: How did so many pieces of Vesta end up right here on our own planet?

For many years, researchers have been collecting Vesta meteorites from "fall sites" around the world. The rocks' chemical fingerprints leave little doubt that they came from the giant asteroid. Earth has been peppered by so many fragments of Vesta, that people have actually witnessed fireballs caused by the meteoroids tearing through our atmosphere. Recent examples include falls near the African village of Bilanga Yanga in October 1999 and outside Millbillillie, Australia, in October 1960.

"Those meteorites just might be pieces of the basin excavated when Vesta's giant mountain formed," says Dawn PI Chris Russell of UCLA.

Russell believes the mountain was created by a 'big bad impact' with a smaller body; material displaced in the smashup rebounded and expanded upward to form a towering peak. The same tremendous collision that created the mountain might have hurled splinters of Vesta toward Earth.

"Some of the meteorites in our museums and labs," he says, "could be fragments of Vesta formed in the impact -- pieces of the same stuff the mountain itself is made of."

End Excerpt.

Dawn has found Vesta to be fascinating. The asteroid is really a small planet, differentiated into a core, mantle, and crust just like a full sized planet (unlike other asteroids which are generally just a mix-and-match of material. It's circular shape and discernable landscape give Vesta the designation Dwarf Planet rather than asteroid. It is believed Vesta was on it's way to becoming a planet when something disrupted it's formation.

Vesta, at 330 miles in diameter, is second only to Ceres in size as asteroids go. Smaller than many of the Kuiper Belt Objects (KBO's) it is composed of rocky material like a terrestrial planet, unlike the KBO's which are primarily ice and frozen gases, similar to comets. (Pluto and her moon Charon are considered KBO's, as are many newly discovered bodies beyond Neptune such as Svedna.)

The problem with all asteroids is that they are subject to too much gravitational influence from Jupiter. Jupiter disrupted the accretion process that led to the formation of large planets, thus leaving a whole lot of debris in an orbit between Mars and Jupiter. Another terrestrial planet could have formed there - and possibly one capable of sustaining life; the asteroid belt is on the edge of the liquid water band, albeit at the outside of that band. Of course, without an atmosphere, liquid water is impossible on the asteroids, and there is a fair amount of ice out there. Actually, liquid water could be possible inside an asteroid; perhaps life formed in caverns? We won't know until we get a good look, and that is likely to be a while.

But we're getting our FIRST look at them, and what we are learning is that we have much to learn. These are exciting times.

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