Alter (Moon)

Named after Dinsmore Alter - American astronomer, meteorologist (1888-1968).

Alter is a lunar impact crater that is located in the northern hemisphere on the far side. It lies to the southwest of the larger crater Robertson, and to the east of Ohm. The outer rim has been degraded by subsequent erosion, most notably at the northern and southern extremes. There is a small crater lying across the south-southeast rim. (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.