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Light Outcrop on Crater Floor
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Light Outcrop on Crater Floor

March 29, 2007

This HiRISE image shows part of the floor of a large impact crater in the southern highlands, north of the giant Hellas impact basin. Most of the crater floor is dark, with abundant small ripples of wind-blown material. However, a pit in the floor of the crater has exposed light-toned, fractured rock.

The light-toned material appears fractured at several different scales. These fractures are called joints, and result from stresses on the rock after its formation.

Joints are similar to faults, but have undergone virtually no displacement. With careful analysis, joints can provide insight into the forces that have affected a unit of rock, and thus into its geologic history. The fractures appear dark; this may be due to trapping of dark, wind-blown sand in the crack, to precipitation of different minerals along the fracture, or both.

Observation Geometry

Image PSP_001860_1685 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 19-Dec-2006. The complete image is centered at -11.3 degrees latitude, 69.4 degrees East longitude. The range to the target site was 261.2 km (163.3 miles). At this distance the image scale ranges from 26.1 cm/pixel (with 1 x 1 binning) to 52.3 cm/pixel (with 2 x 2 binning).

The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 03:40 PM and the scene is illuminated from the west with a solar incidence angle of 59 degrees, thus the sun was about 31 degrees above the horizon. At a solar longitude of 152.8 degrees, the season on Mars is Northern Summer.



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