The Asteroid Queen

摘要

The largest asteroid of all, Ceres, is even more of a mystery than Vesta was before Dawn arrived. Most of what astronomers know about Ceres comes from indirect measurements of its mass and density, based on the way it subtly tugs on Mars and vice versa. "It density suggests an awful lot of water," says Dawn mission leader Chris Russell. "And the shape is consistent with a core of silicate rock, with ice and water on the outside. So we think we're going to find a very water-rich protoplanet out there. Ceres has a radius of 310 miles, and we think 62 miles of that is water."