There could be H2O ice on Vesta

Vesta is the second biggest asteroid in the famous asteroid belt between Mars and Jupiter. It has generally been thought that Vesta would get enough sun over its entire surface that water would not survive, but a recent survey of the surface indicates that deeply buried water has a chance of remaining on the asteroid near the poles, or possibly at the bottom of some deep craters.

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Vesta Up Close (image by NASA)

This is interesting, in part, because of questions about the role of water in the early formation of the solar system. One of the main objectives of the Dawn spacecraft mission is to examine water (or the lack of water) on Vesta and Ceres (another asteroid).

Dawn is looking for water using the gamma ray and neutron detector (GRaND) spectrometer, which can identify hydrogen-rich deposits that could be associated with water ice. The spacecraft recently entered a low orbit that is well suited to collecting gamma ray and neutron data.

“Our perceptions of Vesta have been transformed in a few months as the Dawn spacecraft has entered orbit and spiraled closer to its surface,” says Lucy McFadden, a planetary scientist at NASA Goddard and a Dawn mission co-investigator. “More importantly, our new views of Vesta tell us about the early processes of solar system formation. If we can detect evidence for water beneath the surface, the next question will be is it very old or very young, and that would be exciting to ponder.”

The modeling done by Stubbs and Wang, for example, relies on information about Vesta’s shape. Before Dawn, the best source of that information was a set of images taken by NASA’s Hubble Space Telescope in 1994 and 1996. But now, Dawn and its camera are getting a much closer view of Vesta.

“The Dawn mission gives researchers a rare opportunity to observe Vesta for an extended period of time, the equivalent of about one season on Vesta,” says Stubbs. “Hopefully, we’ll know in the next few months whether the GRaND spectrometer sees evidence for water ice in Vesta’s regolith. This is an important and exciting time in planetary exploration.”

NASA press release