Original: With somewhat oblong diameters of 350 -- 500 km , and a mass estimated to be 2.9 % of the total mass of the belt , '' Mass of 10 Hygiea '' 0.445 / '' Mass of Mbelt '' 15 = 0.0296 it is the fourth largest object in the region by volume and mass .
Simplified: 10 Hygiea is the fourth biggest object in the asteroid belt , somewhat non-spherical with diameters of 350 -- 500 km and a mass estimated to be 3 % of the total mass of the asteroid belt .