The Orientale Basin is located near the western limb of the lunar nearside and is only partially visible from telescopes on Earth. Lunar orbiter images provided the first good look at this basin, which is 930 kilometers in diameter. Material from this basin was not sampled by the Apollo program, so the basin's precise age is not known. However, it is the freshest impact basin on the Moon and is believed to be slightly younger than the Imbrium Basin, which formed about 3.85 billion years ago.
Unlike most other basins on the Moon, Orientale is relatively unflooded by mare basalts, exposing much of the basin structure to view. As a result, study of the Orientale Basin is important to our overall understanding of the geology of large impact basins. There are three prominent basin rings in this image. From the inside out, they are the Inner Rook Mountains, the Outer Rook Mountains, and the Cordillera Mountains. The Cordillera Mountains are regarded as the rim of the basin, defining the basin's 930-kilometer diameter.
This image was taken by Lunar Orbiter 4.
Image Credit: NASA
Credit: Lunar and Planetary Institute