Vesta as seen by Dawn. Credit: NASA/JPL-Caltech
Somewhere in the Asteroid Belt, NASA's plucky spacecraft Dawn is on its way from Vesta, the second-largest object in the belt, to Ceres, the largest. Having finished with the spacecraft's time at Vesta, scientists are now parsing the mound of data they accumulated about the big rock and uncovering some surprises. One of them: It's got water.
According to a couple of complementary studies that appear in the journal Science today, Vesta was thought to be bone dry. The information for Dawn shows, however, that regions near Vesta's equator had enough hydrogen to account for a water content as high as 400 parts per million, according to Nature. It may not sound like much, but?like the traces of water our satellites are finding on the moon?it's enough to make planetary scientists wonder, and to reinforce the idea that the solar system is a surprisingly watery place.
Besides its surprising moisture, Vesta is also interesting because it might be a window to the early days of the solar system. Earlier this year Dawn scientists confirmed that, as suspected, Vesta is the source of a class of meteorites that represents one in 20 that strike the Earth. Data from those asteroids and from the Dawn spacecraft confirmed that Vesta is no ordinary asteroid, but was probably on its way to becoming a planet before it was ripped apart, possibly by the immense gravitational tug of Jupiter.
And then there's Ceres, the next destination for Dawn. It's so big some scientists called it a planet after its discovery two centuries ago. Now it's classified as a dwarf planet, the same as Pluto. Dawn should arrive in 2015 and begin to find out what mysteries lie beneath Ceres' surface.
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