On March 6, 2015 at 7:39 a.m. EST, NASA’s Dawn spacecraft became the first to achieve orbit around a dwarf planet — Ceres. It is also the first mission to orbit two extraterrestrial targets – Ceres and Vesta. Ceres and Vesta are the two most massive bodies of an asteroid belt between Mars and Jupiter.
The spacecraft was launched from Cape Canaveral, Florida on September 27, 2007 and explored Vesta from 2011 to 2012, sending new insights and thousands of images back to Earth.
Dawn discovered that Vesta may have had short-lived water flows on the surface and may now have localized patches of ice below its surface. Scientists are not sure where the water/ice came from. However, they guess that ice-rich bodies like comets, left part of their ice under the surface after impact.
During its time visiting Vesta, Dawn discovered narrow curved gullies that are about 100 feet (30 meters) wide. Their average length is about half a mile (900 meters). The gullies appear different than they would if formed by the flow of purely dry materials. Scientists believe that water debris flows formed the gullies.
“We’re suggesting a process similar to debris flows, when a small amount of water mobilizes the sandy and rocky particles into a flow,” explained Jennifer Scully, postgraduate researcher at the University of California, Los Angeles.
Craters with curvy gullies appear to be less than a few hundred million years old, which is still young compared to Vesta’s age of 4.6 billion years.
Laboratory experiments performed at NASA’s Jet Propulsion Laboratory in Pasadena, California, show that there could have been enough time for the gullies to form before all water evaporated from the surface of Vesta.
Ceres was discovered in 1801 and has been known as a planet, an asteroid, and now a dwarf planet.
As big as Texas, Ceres has a spherical body, like Earth that is denser material at the core and lighter minerals near the surface. Astronomers believe that water ice may be buried under its crust because its density is less than that of Earth’s crust, and because the dust-covered surface includes evidence of water-bearing minerals. It is also possible that the planet has frost-covered polar caps. Water ice is expected to be located in its mantle.
Astronomers guess that if Cere were composed of 25 percent water, it may have more water than all the fresh water on Earth.