Thursday, May 20, 2010

Gullies and Flow Features on Crater Wall

This HiRISE image shows a sample of the variety and complexity of processes that may occur on the walls of Martian craters, well after the impact crater formed.

At the very top of the image is the high crater rim; at the bottom of the image is the crater's central peak - a dome of material rising above the surrounding crater floor uplifted during the impact event.

Reaching down the walls of the crater are windy and crooked troughs, or gullies. Some of these gullies may have formed with the help of liquid water, melted from ice or snowpack on the crater walls or from groundwater within the walls. Also notable is the long tongue-like lobe stretching down the middle of the image, with a darker, rounded snout, and prominent parallel grooves on its surface. These characteristics, together with faint cracks on its surface, suggest that this lobe may have formed by movement of ice-rich material from up on the crater wall down to the crater floor.

Because surface features on this lobe, as well as most gullies, do not appear sharp and pristine, and wind-blown dunes have blown up on the front snout of the lobe, and because there are several small craters on the lobe's surface, the movement of ice-rich material, and possibly water, have probably not occurred very recently.

This image forms a stereo pair with ESP_013871_1475.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in the Promethei Terra region of Mars, which is located to the northeast of Hellas Planitia.

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