谷神星, known as Ceres, is the largest object in the asteroid belt between Mars and Jupiter. Discovered in 1801 by Giuseppe Piazzi, it was initially classified as a planet but later redefined as a dwarf planet in 2006 by the International Astronomical Union. Ceres has a diameter of about 940 kilometers and is composed mainly of water ice and rock. It features a variety of surface features, including craters and bright spots, which are believed to be salt deposits. Ceres is also of interest for its potential to harbor water, making it a target for future exploration.