This image of the giant asteroid Vesta was taken by NASA’s Dawn spacecraft, as part of a rotation characterization sequence on July 24, 2011

Excerpt from natmonitor.com


NASA’s Dawn spacecraft currently approaching the dwarf planet Ceres, the largest object in the asteroid belt that between Mars and . However, from 2011 to 2013 Dawn collected extensive data on Vesta, the second largest object in the asteroid belt and one of the largest known comets in our solar system.

The data collected from Vesta is still being analyzed and will to be for years to come. As the data is examined interesting new information about the giant asteroid is coming to light. Vesta which is very cold and has no atmosphere has long thought to be dry. A new study published in the journal Earth and Planetary Science Letters casts on that assumption.
While there are certainly no rivers and lakes on Vesta, photographs taken by Dawn show evidence of short lived flows of mobilized material on the surface.

“Nobody expected to find evidence of water on Vesta. The surface is very cold and there is no atmosphere, so any water on the surface evaporates. However, Vesta is proving to be a very interesting and complex planetary body,” said Jennifer Scully, postgraduate at the University of California, Los Angeles in a statement.

The research could change some basic assumptions in planetary science.

“These results, and many others from the Dawn mission, show that Vesta is home to many processes that were thought to be exclusive to planets. We forward to uncovering even more insights and mysteries when Dawn studies Ceres,” said UCLA’s Christopher Russell, principal investigator for the Dawn mission.
The curved gullies on vesta are very different from what would be expected from dry material flows, say the researchers.

“We’re not suggesting that there was a -like flow of water. We’re suggesting a process similar to debris flows, where a small amount of water mobilizes the sandy and rocky particles into a flow. These features on Vesta share many characteristics with those formed by debris flows on Earth and Mars,“ said Scully.

The leading so far is that Vesta has small patches of ice beneath the surface, possibly deposited by impacts from other comets. Later impacts could have heated the ice enough to thaw some of the water, releasing it into the crater.