Mare Orientale - Geology

Geology

During the 1960s, rectified images of Mare Orientale by Gerard Kuiper at the Lunar and Planetary Laboratory gave rise to the notion of it being an impact crater. The mare is about 900 kilometres (560 mi) across and was formed by the impact of an asteroid-sized object. Unlike most other basins on the Moon, Orientale is relatively unflooded by mare basalts, exposing much of the basin structure to view; the central portion of Mare Orientale is covered by a thin layer of mare basalt probably less than 1 kilometer deep, much less than in other nearside mare basins. The collision caused ripples in the lunar crust, resulting in the three concentric circular features. The innermost rings of this vast, multi-ringed crater are the inner and outer Montes Rook, and the outermost ring are the Montes Cordillera, 930 km in diameter. Basin ejecta begins just outside the Montes Cordillera and extends up to 500 kilometers beyond the base of the mountains. This ejecta has a rough, hummocky texture and contains linear patterns that point back toward the center of Mare Orientale.

Material from Mare Orientale was not sampled by the Apollo program so the basin's precise age is not known. However, it may be 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. The surrounding basin material is of the Lower Imbrian epoch with the mare material being of the Upper Imbrian epoch.

Located at the antipode of Mare Orientale is Mare Marginis.