Challis (Moon)

Named after James Challis - British astronomer, mathematician, physicist (1803-1882).

Challis is a lunar crater that is located in the northern regions 's near side, close enough to the limb to appear significantly foreshortened when viewed from the Earth. It is joined to the crater Main through a break in the northern rim, and is close to Scoresby along the southeast side. The rim of this crater has been damaged and eroded by a history of impacts, with the most intact portion located along the southeastern half. A small crater lies across the southern rim, and the remaining rim is notched and irregular. (wikipedia entry)

A crater is a circular depression likely created by an impact event. On the Moon they are named after deceased scientists, polar explorers, astronauts or cosmonauts.