Eroding Crater Walls

LROC NAC image of the wall of Makelyne B crater showing streaks of high reflectance material that once flowed down the walls
High reflectance material poured down the walls toward the floor of Maskelyne B crater indicating interbedding of high reflectance and low reflectance layers in the walls. Image width is 2800 m and vertical relief is 1300 m (4250 feet). North is up; LROC NAC mosaic M137360167 [NASA/GSFC/Arizona State University].

Maskelyne B is a simple crater in southern Mare Tranquillitatis, and is ~1800 m deep and over 8 km across! The stratigraphy revealed in the walls of the Maskelyne B impact crater are clues to the volcanic history in Mare Tranquillitatis. Perhaps there is older higher reflectance anorthositic material beneath younger and darker basaltic lava flows. Layering also occurs by large impacts ejecting and emplacing older subsurface material on the local terrain. The most likely cause for the layers seen in Maskelyne B is from the erosion of large coherent blocks of unexposed mare basalt over mature space weathered regolith. High resolution spectral imaging or samples of this area would resolve this ambiguity.

The surface of Mare Tranquillitatis was built up over time by lava flows between 3.5 and 3.9 billion years ago creating stratigraphic units that are visible today. Maskelyne B formed long after the lava cooled. As the crater walls are eroded away by smaller impacts, the higher reflectance material is exposed and the surface is ground into boulders, cobbles, and dust.

The contrast between the light boulders and dark slopes draws the eye and piques curiosity to know what lies beneath the surface. See more of Maskelyne B and the surrounding area below.

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Published by Aaron Boyd on 30 May 2014