Eratosthenes 14.5°N, 11.3°W

Eratosthenes is a typical, little-eroded impact crater with a diameter of 58 km. The depth of the crater floor below the rim is 3.6 km. It has a continuous crater rim and strongly terraced inner walls. The central peak reaches a height of 1.5 km above the crater floor. Eratosthenes was formed about 3.2 billion years ago (within the Eratosthenian period on the lunar timescale). Because of its greater age – when comparted with Copernicus (800 million years) – it no longer shows any obvious ray system. The system that formerly existed has, over the course of billions of years, been darkened by lunar erosion and covered by later impacts.

The foothills of the Apennines reach as far as the northeastern wall of the crater. On the southwest lies a nameless range of mountains which stretches south as far as the ghost crater Stadius. The view of Eratosthenes changes greatly throughout a lunation, and at Full Moon it is practically invisible.

Sinus Aestuum 10.9°N, 8.8°W

Sinus Aestuum (‘Bay of Billows’) is a mare-like plain, about 290 km across. It lies between Eratosthenes and the western slopes of the Apennines. The surface shows a few craters and a few ridges similar to mare wrinkle ridges. The low crater count suggests that the lava flows in Sinus Aestuum are relatively young.