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Back to the Birth of the Solar System


By Harlan Lebo

Published Oct 20, 2011 5:00 PM


Artist rendering of the Dawn spacecraft approaching Mars. Illustration credit: NASA/JPL.

The second-largest asteroid in our solar system, Vesta, is small compared to the planets—only 330 miles in diameter. Yet scientists hope it will be a key source of information about how the Earth and other planets were formed.

Vesta is the focal point of a NASA mission with a UCLA-led team of 80 scientists. Since July, following a 1.7 billion-mile voyage from Earth, the Dawn spacecraft has been orbiting Vesta—the first stop in the first unmanned project to closely examine the two largest asteroids.

UCLA space scientist Christopher Russell proposed the mission to NASA in 1994. Now he is the principal investigator.

"Vesta was an active body at one time, trying to do the same things that the Earth does," he says.

Scientists speculate that Vesta once had some of the features of other planets, including active volcanos and water, but it was radically reshaped at some point by a massive collision, from a source still unknown.

Russell hopes the Dawn mission will not only yield new information about Vesta, but will also create new understanding about the evolution of planets like Earth. The cameras, spectrometers, gamma ray detector and other instruments aboard the spacecraft are studying Vesta's visible surface and craters, as well as puzzling shadows and dark spots, using precision orbits that vary in altitude to give each instrument the ideal range to operate.


This image obtained by the framing camera on NASA’s Dawn spacecraft shows the south pole of the giant asteroid Vesta. Photo credit: NASA/JPL-Caltech/ UCLA/MPS/DLR/IDA.

"The team has been in awe of what they have seen," Russell told reporters at a Dawn mission press conference. "There’s so much more going on there than we ever expected. What we found is really a very rich surface."

Like Earth, Mars, Venus and Mercury, Russell says, "Vesta has ancient basaltic lava flows on the surface and a large iron core. It has tectonic features, troughs, ridges, cliffs, hills and a giant mountain."

The first images coming back from Dawn look promising, and some surprises have already appeared. An image of Vesta sent from Dawn in early October shows that the "giant mountain" Russell spoke of rises 13 miles above the surrounding terrain—three times as high as Mt. Everest.

In July 2012, after a year-long investigation of Vesta, Dawn will depart for a three-year, 930-million mile journey to Ceres, the largest asteroid in our solar system, with arrival scheduled for February 2015.

Find regular updates about the Dawn mission—including a new image every day, briefings, background and projects for children—at



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