Linear Dunes and Sand Sheets in Herschel Crater
NASA/JPL/University of Arizona
Linear Dunes and Sand Sheets in Herschel Crater
ESP_016916_1655  Science Theme: Aeolian Processes
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This image shows sand dunes and sheets in the central part of Herschel Crater.

In the Northern (top) part of the image, the dunes grade between two morphologies, "barchan" and "linear." Barchans are crescent-shaped, with the horns of the crescents pointing downwind. One barchan is visible in the upper part of the image, with the Southeast (lower right) horns longer than the other (see subimage, red box). This trend, along with the position of the steep face of the dune on the South side, indicates that the predominant winds which formed the dunes came from the North.

Southward of the barchan, the dunes grade into long streamers, called "linear dunes." On Earth, barchans form in areas of limited sand supply and linear dunes require two dominant wind directions that meet at an acute angle (i.e., less than 90 degrees). South of the linear dunes the sand covers the terrain in a vast sand sheet (see subimage, blue box). Together, these observations suggest that this part of Mars contains a limited supply of sand that has been subjected to high speed winds coming from two northerly directions.

The surface texture on the upper surface of the barchan dune and sand sheet exhibits corrugated patterns not seen on other dune surfaces. This may be caused by induration and subsequent erosion of some of the sand. Such a hypothesis was proposed by earlier investigators using lower resolution data from the Mars Orbiter Camera.

Written by: Nathan Bridges  (29 September 2010)

This is a stereo pair with ESP_017417_1655.
 
Acquisition date
06 March 2010

Local Mars time
15:05

Latitude (centered)
-14.104°

Longitude (East)
129.687°

Spacecraft altitude
259.5 km (161.3 miles)

Original image scale range
26.1 cm/pixel (with 1 x 1 binning) so objects ~78 cm across are resolved

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25 cm/pixel and North is up

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Equirectangular

Emission angle
5.8°

Phase angle
62.3°

Solar incidence angle
58°, with the Sun about 32° above the horizon

Solar longitude
60.4°, Northern Spring

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North azimuth:  97°
Sub-solar azimuth:  42.7°
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POSTSCRIPT
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. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.