The terraced slopes of Aristarchus


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The science team of Lunar Reconnaissance Orbiter released a spectacular image of the lunar crater Aristarchus on Christmas Day, looking sideways at the crater’s west wall. The image was taken from only 16 miles above the Moon’s surface. You can see the full image here.

Wall of Aristarchus

Two things to note from this image:

  • The terraced nature of the crater’s slopes. These terraces were not put there by Chinese farmers. Instead, they show us the slumping downward over time of the crater floor after the initial impact. The various terraces are the result of “the sagging blocks of the pre-impact lunar crust.” In other words, each terrace provides a window into a different epoch of the Moon’s geological history.
  • The crater wall has a remarkable range of bright and dark material. In several places dark volcanic material coated the wall as it tumbled downward. In other areas there are extremely bright deposits, fresh material more recently excavated from beneath the surface. Both types suggest that the geology of Aristarchus is complex, and would provide lunar geologists a wealth of information about the history of the Moon.
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