Aorounga
Just south of the Tibesti mountains (a volcanic range) in northern Chad, an impact crater nearly 13km across is a mute testimony to a huge impact around 340 million years ago back in the early Carboniferous, as Pangaea was assembling. A dark central peak marks where the rocks rebounded upwards on impact, with a second ring of ejected material forming separated from it by a sand filled trough. A second sandy ring then separates the centre from the outer edge of the impact, forming a bullseye figure. The crater may be part of a chain, with two other possible smaller impacts nearby.
The linear ridges of rock are yardangs, eroded by the wind, and indicate Aeolus's prevailing direction in this remote and harsh region of the Sahara. Between the ridges are herds of migrating sand dunes.
Loz
Image credit: ESA