A new study provides evidence that the massive asteroid Vesta once had water on its surface, contradicting an earlier belief that it was incapable of housing the substance.
Vesta is the second largest and the brightest asteroid in the asteroid belt, and was discovered in 1807. Unlike other asteroids, it is considered a protoplanet with a surface about three times more luminous than earth's moon. Scientists thought that it is completely dry because its surface has very low temperatures and pressures. But a new study has challenged that belief.
"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," said Jennifer Scully, a postgraduate researcher at the University of California, Los Angeles, in a statement. "However, Vesta is proving to be a very interesting and complex planetary body."
Scully's team spotted a small number of craters on Vesta with narrow, curved gullies that are 30 meters wide and 900 meters long. It also has fan-shaped deposits suggesting that water might have flowed on its surface some time ago.
"These features on Vesta share many characteristics with those formed by debris flows on Earth and Mars," Scully said.
The researchers presume that the water might have come from icy comets that collided with the asteroid and that there are some that were trapped on Vesta's surface. Dawn's visible and infrared mapping spectrometer and gamma ray and neutron detector also found traces of water on the asteroid's surface that are younger than the asteroid's age.
"These results, and many others from the Dawn mission, show that Vesta is home to many processes that were previously thought to be exclusive to planets," said UCLA's Christopher Russell, principal investigator for the Dawn mission. "We look forward to uncovering even more insights and mysteries when Dawn studies Ceres."
The Dawn mission is a space probe launched by NASA in 2007 to study the two massive asteroids in the asteroid belt-- protoplanet Vesta and dwarf planet Ceres. It aims to gather clues so that we can better understand the evolution and formation of our Solar System. If its mission timeline remains the same, it is expected to reach Ceres next month after leaving Vesta in July 2012.
The study was published in the Earth and Planetary Science Letters.
