May 28, 2012
Anorthosite Rays
image by Mario Weigand, Offenbach am Main / Germany
Once again the LPOD Photo Gallery has provided an image for LPOD. In this case it is Mario's excellent view
of bright Anaxagoras overlapping shallow Goldschmidt to the right, with the even brighter simple crater Epigenes A
to the bottom right. The pudgy central mountains of Anaxagoras are pure anorthosite - plagioclase feldspar - a
mineral that is thought to have formed the calcium-rich crust above the magma ocean. Continuous ejecta and rays
from the crater that drape across Goldschmidt are also anorthositic. Mario's image shows better than I've noticed
elsewhere two broad zones of material on the western wall and continued beyond the rim crest down the exterior
wall. Although the distribution of rays and impact melt imply that Anaxagoras formed by oblique impact with the
projectile coming from the west, it seems most likely that the wall zones are bright (hence anorthosite) material
ejected during formation of the crater.
Chuck Wood
Related Links
Rükl plate 4
Mario's website
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