NASA’s Dawn Spacecraft has revealed the giant asteroid, has its own version of ring around the collar, based on observations from the low-altitude mapping orbit of the Dawn mission, show volatile, or easily evaporated, materials have coloured Vesta’s surface in a broad swath around its equator.
The Spacecraft did not find actual water ice at Vesta.But, it found evidence of hydrated minerals delivered by meteorites and dust in the giant asteroid’s chemistry and geology,the volatiles were released from minerals likely containing water. Pothole-like features mark some of the asteroid’s surface where the volatiles boiled off.
Thomas Prettyman, the lead scientist for Dawn’s gamma ray and neutron detector describes how the instrument found signatures of hydrogen, likely in the form of hydroxyl or water bound to minerals in Vesta’s surface,the source of hydrogen within Vesta’s surface appears to be hydrated minerals delivered by carbon-rich space rocks that collided with Vesta at speeds slow enough to preserve their volatile content.
Another study, led by Brett Denevi, a Dawn participating scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel,revealed the presence of pitted terrain created by the release of the Vesta is the second most massive member of our solar system’s main asteroid belt. Dawn was orbiting at an average altitude of about 130 miles above the surface when it obtained the data.
Scientists thought it might be possible for water ice to survive near the surface around the giant asteroid’s poles. Unlike Earth’s moon, however, Vesta has no permanently shadowed polar regions where ice might survive. The strongest signature for hydrogen in the latest data came from regions near the equator, where water ice is not stable.
In some cases, space rocks crashed into these deposits at high speed. The heat from the collisions converted the hydrogen bound to the minerals into water, which evaporated. Escaping water left holes as much as six-tenths of a mile (1 kilometer) wide and as deep as 700 feet (200 meters). Seen in images from Dawn’s framing camera, this pitted terrain is best preserved in sections of Marcia crater.