Researchers say they aren't sure what has carved the gullies -- some straight, some sinuous ending in delta-like deposits -- into the surface of the giant asteroid.
Dawn team members presented imaged of the gullies at this week's American Geophysical Union conference in San Francisco.
"The straight gullies we see on Vesta are textbook examples of flows of dry material, like sand, that we've seen on Earth's moon and we expected to see on Vesta," said Jennifer Scully, a Dawn team member at the University of California, Los Angeles. "But these sinuous gullies are an exciting, unexpected find that we are still trying to understand."
The scientists said they think different processes formed the two types of gullies and hope images of Earth, Mars and other small solar system bodies may offer clues.
"On Earth, similar features -- seen at places like Meteor Crater in Arizona -- are carved by liquid water," said Christopher Russell, Dawn's principal investigator, also based at UCLA. "On Mars, there is still a debate about what has caused them. We need to analyze the Vesta gullies very carefully before definitively specifying their source."
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