As scientists examine images taken by the Dawn Spacecraft of asteroid Vesta, strange gullies suggest that Vesta was once home to liquid water.
According to NASA, Vesta was visited by the Dawn Spacecraft between 2011 and 2013. However, scientists never expected to find any signs of liquid water, as scientists had deemed that Vesta should be “completely dry, incapable of retaining water because of the low temperatures and pressures at its surface.” However, they were shocked to learn that Vesta was not only capable of short-lived flows of water, but actually had in the recent past.
— NASA (@NASA) January 22, 2015
Jennifer Scully, a postgraduate researcher at the University of California, says that the findings are very interesting.
“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.”
The discovery was made by examining a number of photos taken of young craters on Vesta’s surface. The team found that a number of the craters had “curved gullies and fan-shaped (“lobate”) deposits,” which indicated liquid water had once flowed through those areas. Scully points out that this does not indicate long-lived flows or “river-like” flows, but instead simply suggests that somehow small amounts of water were able to mobilize on the surface and carry sediment.
“We’re not suggesting that there was a river-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.”
However, even a small amount of mobilized water on the surface of Vesta came as a huge surprise to the researchers. It has been determined that the flow was not made by strictly solid materials like a landslide, but rather had to contain liquid.
“The curved gullies are significantly different from those formed by the flow of purely dry material. ‘These features on Vesta share many characteristics with those formed by debris flows on Earth and Mars'”
One theory the scientists have about the source of the water is that Vesta is home to “small, localized patches of ice in its subsurface.” However, the origin of how that ice made it to the subsurface is not known. One theory is that ice-rich bodies such as comets may have left some of the ice below the surface after making impact with Vesta.
Interestingly, it is not only the gullies that suggest hydration on Vesta’s surface. In fact, infrared mapping indicated that hydrated material lies within some rocks on Vesta’s surface, meaning the asteroid is not dry as previously suspected.
“Evidence from Dawn’s visible and infrared mapping spectrometer and gamma ray and neutron detector indicates that there is hydrated material within some rocks on Vesta’s surface, suggesting that Vesta is not entirely dry.”
The Dawn Spacecraft, which is responsible for providing the information to make these amazing new discoveries, is currently investigating the planet Ceres.