Pytheas (Moon)

Named after Of Marseilles Pytheas - Greek navigator, geographer (c. 308 B.C.).

Pytheas is a small lunar impact crater located on the southern part of the Mare Imbrium, to the south of the crater Lambert. It has a sharply defined rim, a hummocky outer rampart, and an irregular interior due to slumping or fall-back. There is a small crater along the northern outer rampart, and a similar crater about 20 km to the west. The crater possesses a small ray system that extends for a radius of about 50 kilometers. (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.