Hardened Dunes in Arcadia Planitia
NASA/JPL/University of Arizona
Hardened Dunes in Arcadia Planitia
ESP_038143_2205  Science Theme: Aeolian Processes
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HiRISE, with its high resolution and 8 years in orbit about Mars, has shown that many dunes and ripples on the planet are active. This demonstrates that in some areas sand is loose enough and winds strong enough, that significant change can occur.

Nevertheless, other Martian dunes are clearly *inactive*. This image in Arcadia Planitia shows dunes in a crater. Unlike active dunes on the planet, those here are bright, and, zooming in, there are several lines of evidence indicating that the dunes have become indurated, that is, hardened into cohesive sediment or even into sandstone rock. For example, the dune field at the southern edge is cut off by a step cliff, indicating erosion of hard material. Although fine scale ripples on the original dune surface are preserved, we also see large scale fluting from southwest to northeast, a common texture associated with wind-induced sand abrasion.

How these dunes became indurated is unknown. One possibility is that this area of Mars was buried and then exhumed, a process that seems to have occurred many times in the Martian past over various areas of the planet . During burial, compaction and possibly ground water circulation would have indurated the dunes, leaving them as a hard sandstone that, when exhumed, was subsequently partially eroded.

Note: a version of the cutout is with only the scale bar is here.


Written by: Nathan Bridges  (29 October 2014)

This is a stereo pair with ESP_055536_2205.
 
Acquisition date
15 September 2014

Local Mars time
15:39

Latitude (centered)
39.983°

Longitude (East)
202.596°

Spacecraft altitude
298.7 km (185.7 miles)

Original image scale range
29.9 cm/pixel (with 1 x 1 binning) so objects ~90 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
3.4°

Phase angle
66.0°

Solar incidence angle
69°, with the Sun about 21° above the horizon

Solar longitude
196.7°, Northern Autumn

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North azimuth:  96°
Sub-solar azimuth:  335.5°
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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.