Layers in Spallanzani Crater PSP0034421215 Subimage
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Layers in Spallanzani Crater PSP_003442_1215 Subimage

July 14, 2007
This image shows light-toned layered deposits along the floor of Spallanzani crater, a 72 kilometer (45 mile) diameter crater located just southeast of Hellas Planitia.

These layered deposits may be remnant sediments once deposited within the crater. Mechanisms for sediment deposition include windblown debris, airfall volcanic ash, or sediments that accumulated in a lake on the crater floor.

The layers within Spallanzani Crater are eroding in a stair-stepped pattern. Each layer appears as a sequence of a broad flat area or plateau, which drops off abruptly down to the next flat surface (see subimage). This stair-stepped pattern suggests that the layers have discreet boundaries that may be the result of differing compositions, time of deposition, or both. Near, but not at the edge of each plateau, the material is fracturing into polygonal plates or blocks that tilt downward away from the plateau center (see subimage).

The slopes are covered in debris, and not fallen plates or blocks from the plateau edge. This suggests that the layers are composed of weak materials that are protected by a stronger, more coherent surface.

The crater is named after the 18th century Italian biologist, Lazzaro Spallanzani (1729-1799).

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