Southern Dunes and Spiders
Southern Dunes and Spiders
PSP_006538_1035  Science Theme: Aeolian Processes
This image gives a rare glimpse of an area in the far south of Mars that is frequently obscured by clouds or covered by surface frosts.

Crescent-shaped sand dunes can be seen scattered across patterned ground. The surface patterns are made up of channels carved by carbon dioxide gas as it escapes from under the seasonal frost. The dunes were still partially frozen when this picture was taken during the vernal equinox, as the Sun moved into the northern hemisphere at the end of the southern summer. Bluish ice is visible on the steep faces of the dunes and along their bases.

Typical sand dunes on Earth and Mars gradually move downwind as sand accumulates on the upwind (convex) side and then avalanches down the steeper down-wind side, called the “slip face”. Here, the sand motion appears to be around the dunes instead. Clean patches of ground downwind of the dunes show that the surface is sheltered by the dunes, which prevent dark sand from being deposited in their lees.

Written by: Paul Geissler  (23 January 2008)
Acquisition date
18 December 2007

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
246.4 km (153.1 miles)

Original image scale range
49.3 cm/pixel (with 2 x 2 binning) so objects ~148 cm across are resolved

Map projected scale
50 cm/pixel

Map projection

Emission angle

Phase angle

Solar incidence angle
83°, with the Sun about 7° above the horizon

Solar longitude
4.6°, Northern Spring

For non-map projected images
North azimuth:  102°
Sub-solar azimuth:  53.7°
Black and white
map projected  non-map

IRB color
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Merged IRB
map projected

Merged RGB
map projected

RGB color
non-map projected

Black and white
map-projected   (858MB)

IRB color
map-projected   (381MB)

Black and white
map-projected  (584MB)
non-map           (617MB)

IRB color
map projected  (238MB)
non-map           (432MB)

Merged IRB
map projected  (860MB)

Merged RGB
map-projected  (823MB)

RGB color
non map           (436MB)
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products

IRB: infrared-red-blue
RGB: red-green-blue
About color products (PDF)

Black & white is 5 km across; enhanced color about 1 km
For scale, use JPEG/JP2 black & white map-projected images

All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible:

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.