Glossary: Moon - Elliptical Craters

When an object hits the surface at a very low angle (close to horizontal), an elongated, elliptical crater can form.

Shown here is the crater pair Messier and Messier A, located in Mare Fecunditatis on the eastern near side of the Moon. The elliptical crater Messier (on the right) is 9 km wide and 11 km long, while Messier A is mostly circular, about 9 km in diameter. The impactor that created this crater pair came in almost horizontally, grazed the lunar surface, creating the elongated Messier crater, then skipped and ploughed into the ground creating Messier A.

Explore this unusual crater pair in more detail by viewing the Lunar Reconnaissance Orbiter Camera data at the LROC ACT-REACT Quick Map Website.

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