Snellius (Moon)

Named after Snell, Willebrod van Roijen Snellius - Dutch mathematician, astronomer, optician (1580-1626).

Snellius is a lunar crater located near the southeast limb. The rim is heavily worn and eroded, with overlapping craterlets. The floor is somewhat irregular and uneven. The western rim marks the start of the Vallis Snellius, one of the longest valleys. (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.