10 Hygiea is a large asteroid located in the outer main asteroid belt between the orbits of Mars and Jupiter. It was the tenth known asteroid, discovered on 12 April 1849 by Italian astronomer Annibale de Gasparis at the Astronomical Observatory of Capodimonte in Naples, Italy. It was named after Hygieia, the Greek goddess of health. It is the fourth-largest main-belt asteroid by both volume and mass, with a mean diameter of 433 km (269 mi) and a mass constituting 3% of the main asteroid belt's total mass.
Hygiea has a nearly spherical shape, with two known craters about 100 and 180 km (62 and 112 mi) in diameter. Because of its shape and large size, some researchers consider Hygiea a possible dwarf planet. Hygiea has a dark, carbonaceous surface consisting of hydrated and ammoniated silicate minerals, with carbonates and water ice. Hygiea's subsurface likely contains a large fraction of water ice. These characteristics make Hygiea very similar to the main-belt dwarf planet Ceres, which suggests the two objects have similar origins and evolutionary histories.
