The rim of a fracture inside the crater Sarton Y. To the left of the rim is outside the fracture, and to the right of the rim is inside the fracture. Image width is 825 meters, LROC NAC frame M140697409L [NASA/GSFC/Arizona State University].
In the highlands at 51.3°N, 121.4°W Sarton Y and Z stand out among the other craters. Take a look at this area in the LROC WMS Image Map. Other craters in the region have filled floors, however, Sarton Y and Z are the only two craters to also have floor fractures. Why is this? What makes Sarton Y and Z special? Perhaps the subsequent impact of Sarton Y allowed the material in both craters to undergo a thermal evolution different from their surrounding counterparts, possibly causing the fractures as the floors cooled. Was there a difference in the surface material when Sarton Y and Z were formed? Both craters show evidence of slumping, but so do the other craters in the region. Age or the composition of the impactor may also play a role.
LROC WAC 100 m/pixel mosaic of Sarton Y and Sarton Z. The red asterisk shows the location of today's featured image [NASA/GSFC/Arizona State University].