Named after Matvei M. Gusev - Russian astronomer (1826-1866).
The crater is about 166 kilometers in diameter and formed approximately three to four billion years ago. A channel system named Ma'adim Vallis drains into it that probably carried liquid water, or water and ice, at some point in Mars' past. The crater appears to be an old crater lake bed, filled with sediments up to 3000 feet thick. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Mars large craters are named after deceased scientists, writers and others who have contributed to the lore of Mars. Small creaters (less than 60km) are named after small towns and villages.
