Exposed Fractured Bedrock in the Central Peak of the
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Exposed Fractured Bedrock in the Central Peak of the Anaxagoras Crater

November 29, 2012
The lunar highlands are thought to have formed as a result of a global melting event early in the Moon’s history, during which plagioclase floated to the top of the ocean and solidified as an upper layer of anorthosite. The study of anorthosite occurrence is thus important for investigating the global magma ocean concept and the evolution/development of the lunar crust. Anaxagoras is a 50 km diameter Copernican impact crater at 73.4°N, 10.1°W, with an extensive ray system (reaching over 900 km from the crater rim in some directions), and a central peak of pure anorthosite. The central peak and the material ejected and deposited onto the floor of Goldschmidt crater to the east, indicates that the Anaxagoras crater-forming impact excavated pure anorthosite. Consequently it is one of the NASA Program regions of interest targeted by LROC. The smaller mound, in the right of Figure 2, is covered with large boulders, up to 30 meters (90 feet) across. Since the boulders cluster on top of topographic highs and are rare on the surrounding flat surfaces, they most likely were not thrown in from afar but rather are eroding out of the substrate. Fig. 2 - LROC WAC image of Anaxagoras crater, arrow indicates location of Featured Image, ~50 km diameter, north is up. Credit: NASA/GSFC/Arizona State University.

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