- Ceres is the largest body in the asteroid belt, the field of rocks that lies between the orbits of Mars and Jupiter. The Dawn spacecraft has been orbiting Ceres since March 6, 2015, its second stop after spending 14 months at the asteroid Vesta. As Dawn loops around Ceres, slight changes in the speed of the spacecraft — deviations of less than 0.1 millimeters per second — reveal the dwarf planet’s gravity field. By combining these measurements with images that show the overall shape of Ceres, the researchers deduced how mass is spread out inside. The core has a density similar to some meteorites; the shell (roughly 70 to 190 kilometers thick) is about two-thirds as dense.
Time to think about a lander and return mission!