Marvin Crater

Rim of Marvin crater
The rim of Marvin crater  (4.6-kilometer diameter) arcs across the image from left to right. The steep interior wall below the rim slopes down toward the bottom of the image. The crater interior is in permanent shadow; the exterior was in shadow when this image sequence was acquired (28 February 2023). However, this area is not permanently shadowed. The image width is 2200 meters, and the south pole is about 26 kilometers to the right, a mosaic made from ShadowCam images M017882983, M017890053, and M017904198 (NASA/KARI/Arizona State University).

Marvin crater honors Ursula Marvin, a pioneering planetary geologist. Dr. Marvin was a historian, economic geologist, meteoriticist,  an early advocate of continental drift (later called plate tectonics), and an Apollo sample expert.  Twice she joined early expeditions to collect meteorites in Antarctica. Truly she was a pioneering scientist!  And, oh yes, she was also an avid bird watcher. The International Astronomical Union honored her varied accomplishments by naming one of the Shackleton - de Gerlache area craters after her.

Look closely at the inside and outside of Marvin crater. At first, the landforms seem normal; however, pay close attention to the lighting. Since the area is illuminated with secondary lighting (primary light reflected into shadowed areas off nearby mountains), you can easily spot large differences in the direction of the lighting. Inside Marvin crater along the rim, note how the light direction wanders from the lower left, direct left, and upper left. Now compare the lighting in small craters just inside Marvin crater to those just outside; the lighting direction changes more than 90 degrees in a few hundred meters.

Interpreting landforms under secondary illumination seen in ShadowCam images takes some practice! Note that as you scroll around in the full mosaic, areas under direct sunlight are saturated (uniform white).

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