Scientists have long suspected that Ceres, which is the largest object in the asteroid belt, has an underground layer of ice, a remnant of an ancient ocean, frozen many eons ago. But last month, when NASA's Dawn spacecraft approached a dwarf planet, scientists were amazed at what they saw: a bright spot on the surface.
“This something has a high reflectivity that at least surpasses that of the rest of the surface,” said Mike Miller, vice president of science programs.
"This may be fresh material released to the surface relatively recently, or it may be a consequence of any chemical reactions," added Joe Makovsky, Mission Manager Dawn.
Based on the round shape and relatively low density, computer models show that Ceres has a stone core and an ice mantle covered with a layer of dust, clay, and sediment.
"Ceres is lighter than rocky planets. This means that it retained a lot of water and other lighter elements that were present in the solar system when Ceres was formed. Unlike her, other objects such as the Moon and the asteroid Vesta are dry and stone, ”says Carol Raymond, deputy lead scientist for the Dawn mission at NASA's Jet Propulsion Laboratory in Pasadena, California.
This makes Ceres similar to such objects as Europe and Enceladus - two ice satellites of Jupiter, which have underground oceans.
This increases the likelihood that Ceres had the conditions and chemical composition favorable for the origin of life.
"We believe that Ceres has astrobiological potential," said Raymond.
A liquid layer of water under the surface of Ceres is now unlikely, but the 600-mile protoplanet promises surprises.
In addition to the mysterious bright spots on its surface, Ceres periodically throws water vapor into space. Scientists suggest that when colliding with comets or asteroids, the surface containing ice may heat up, forming geysers.
NASA sent Dawn in the hope of finding out what role similar objects play in the origin and development of the Earth and other planets. The spacecraft will go into orbit around Ceres on Friday.