Ceres, formal designation 1 Ceres, is the smallest identified dwarf planet in the Solar System and the only one in the asteroid belt. It was discovered on January 1, 1801, by Giuseppe Piazzi, and is named after the Roman goddess Ceres the goddess of growing plants, the harvest, and motherly love.

With a diameter of about 950 km, Ceres is by far the largest and most massive body in the asteroid belt, and contains a third (32%) of the belt's total mass. Recent observations have revealed that it is spherical, unlike the irregular shapes of smaller bodies with lower gravity. The surface of Ceres is probably made of a mixture of water ice and various hydrated minerals like carbonates and clays.

Ceres appears to be differentiated into a rocky core and ice mantle. It may harbour an ocean of liquid water underneath its surface, which makes it a potential target in the search for extraterrestrial life.

Ref: Wikipedia http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)