HiRISE image PSP_003597_1765 shows fractured mounds on the southern edge of Elysium Planitia.

The mounds are typically a few kilometers in diameter and about 200 feet tall. The fractures that crisscross their surfaces are dilational (extensional) in nature, suggesting that the mounds formed by localized uplift (i.e., they were pushed up from below).

The mounds are probably composed of solidified lava. They are contiguous with, and texturally similar to, the flood lavas that blanket much of Elysium Planitia, and, where dilation cracks provide cross-sectional exposure, the uplifted material is rocky.

Patches of mechanically weak and disrupted material overlie the rocky mound material. This is particularly conspicuous in the northeast corner of the HiRISE image. These patches may be remnants of a layer that was once more continuous but has been extensively eroded. Smooth lava plains fill the low-lying areas between the mounds. They are riddled with sinuous pressure ridges. The entire area is covered by a relatively thin layer of dust and sand.
Written by: W. L. Jaeger

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For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.