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Crisiums Region of Interest
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Crisium's Region of Interest

November 28, 2012
In the WAC monochrome image, the arrow indicates the location of the NAC frame at the beginning of this post, which shows a portion of a wrinkle ridge. A fascinating feature of this ridge when seen in high resolution is that its face is littered with boulders. Perhaps these boulders are generated by breakup of the of the mare basalt, and they're visible now because of the faulting and folding that caused this ridge. (Judge for yourself in the full-resolution NAC frame here.) Lunar scientists (but not engineers!) love boulders because they usually come from below the surficial regolith layer, and can indicate buried rock units of different compositions. Some have suggested that perhaps Luna 24 sampled a basalt unit that was buried by a subsequent lava flow of a different composition, and only exposed on the surface where impact craters excavated the material from depth. This scenario would explain why spacecraft don't see the sampled material widespread on the surface. Visiting the Crisium region of interest could help scientists unravel this interesting puzzle. A WAC monochrome image centered on the Crisium Constellation region of interest. The highlands area in the south is the rim of the Crisium impact basin and wrinkle ridges and a wrinkle-ridge ring can be seen in the mare to the north. Arrow shows the location of the NAC frame above. Scene is 62 km across; image number M117107778ME Credit: NASA/GSFC/Arizona State University