Onon (Mars)

Named after the Town in Mongolia.

Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger they usually have a central peak. The peak is caused by a rebound of the crater floor following the impact. (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.