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Aram Chaos is thought to be a degraded impact crater that was once filled with water and sedimentary units. The term "chaos" refers to the cracks and angled blocks formed perhaps by withdrawal of subsurface material. This sub-image covers only a small portion of Aram Chaos and illustrates the modification of the crater by fracturing, younger impact craters, and wind. A linear fracture cuts through the center of the image while a more sinuous depression filled with bright ripples or dunes is located towards the bottom of the image. Both depressions could have resulted from collapse associated with modification of the impact crater that created Aram Chaos or later disruption when water and sediment covered some of the crater floor. Impact craters of many shapes and sizes can be seen across the image, indicating a relatively older surface that has seen little modification since its formation. The bright ripples or dunes appear to cluster in low-lying topography, such as the sinuous depression and a larger impact crater in the lower right of the image, suggesting that wind has moved fine material along the surface until it becomes trapped in low spots where it collects to form ripples or dunes.
Image TRA_000834_1835 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on September 30, 2006. The complete image is shown below, centered at 3.3 degrees latitude, 338.1 degrees East longitude. The range to the target site was 273 km (171 miles). At this distance the image scale is 55 cm/pixel (with 2 x 2 binning) so objects ~165 cm across are resolved. The full image (shown at top) has been map-projected to 50 cm/pixel and north is up. The image was taken at a local Mars time of 3:27 PM and the scene is illuminated from the west with a solar incidence angle of 53.8 degrees, thus the sun was about 36.2 degrees above the horizon. At a solar longitude of 113.9 degrees, the season on Mars is Northern Summer / Southern Winter. |
