Ceres and Vesta
Date: 14 May 2007
These Hubble Space Telescope images of Vesta and Ceres show two of the most massive asteroids in the asteroid belt, a region between Mars and Jupiter.
The image at right was taken on 14 and 16 May 2007. Using Hubble, astronomers mapped Vesta's southern hemisphere, a region dominated by a giant impact crater formed by a collision billions of years ago. The crater is 285 miles (456 km) across, which is nearly equal to Vesta's 330-mile (530-km) diameter. If Earth had a crater of proportional size, it would fill the Pacific Ocean basin. The impact broke off chunks of rock, producing more than 50 smaller asteroids that astronomers have nicknamed "vestoids." The collision also may have blasted through Vesta's crust. Vesta is about the size of Arizona.
Hubble's sharp "eye" can see features as small as about 37 miles (60 km) across. The image shows the difference in brightness and color on the asteroid's surface. The brightness differences could be similar to the effect seen on the Moon, where smooth, dark regions are more iron-rich than the brighter highlands that contain minerals richer in calcium and aluminum.
The Hubble image of Ceres on the left, from observations made in visible and ultraviolet light between December 2003 and January 2004 with the Advanced Camera for Surveys, reveals bright and dark regions on the asteroid's surface that could be topographic features, such as craters, and/or areas containing different surface material. Large impacts may have caused some of these features and potentially added new material to the landscape. The Texas-sized asteroid holds about 30 to 40 percent of the mass in the asteroid belt.
Ceres' round shape suggests that its interior is layered like those of terrestrial planets such as Earth. The asteroid may have a rocky inner core, an icy mantle and a thin, dusty outer crust. The asteroid may even have water locked beneath its surface. It is approximately 590 miles (950 km) across and was the first asteroid discovered in 1801.
Last Update: 11 Apr 2011 (AMB)
Credit: NASA/European Space Agency