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"The moment of truth is about to arrive" for protoplanet Vesta: NASA

June 11, 2011 - Washington

NASA's Dawn spacecraft launched in 1997 is now approaching Vesta, a small protoplanet in the asteroid belt between Mars and Jupiter - a destination that is 143 million miles from Earth.

Dawn will arrive at Vesta in July. Beginning in September, the spacecraft will orbit Vesta some 400 miles from its surface. It will then move closer, to about 125 miles from the surface, starting in November. By January of 2012, it is expected to show high-resolution images and other data about surface composition.

Dawn's cameras should be able to see individual lava flows and craters tens of feet across on Vesta's surface.

Dawn has a high-quality camera, along with a back-up; a visible and near-infrared spectrometer that will identify minerals on the surface; and a gamma ray and neutron spectrometer that will reveal the abundance of elements such as iron and hydrogen, possibly from water, in the soil. Dawn will also probe Vesta's gravity with radio signals.

"There are many mysteries about Vesta," said Christopher T. Russell, a UCLA professor of geophysics and space physics in the Department of Earth and Space Sciences, and the mission's principal investigator.

"One of them is why Vesta is so bright. The Earth reflects a lot of sunlight - about 40 percent - because it has clouds and snow on the surface, while the moon reflects only about 10 percent of the light from the sun back. Vesta is more like the Earth. Why? What on its surface is causing all that sunlight to be reflected?

"The moment of truth is about to arrive," Russell added.


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