O'Day (Moon)

Named after Marcus O'Day - American physicist (1897-1961).

O'Day is a prominent lunar impact crater on the far side. It intrudes into the northwestern edge of Mare Ingenii, and the rim is lower on that side. To the northwest is the crater pair of Holetschek and Sierpinski. Southwest lies the crater Seidel. (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.