Canso is a Martian crater. It lies about 450 kilometres west of the Viking 1 lander, slightly northeast of Lunae Planum, and west of Chryse Planitia, in the Lunae Palus quadrangle. Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. (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.