Well-Speckled Polar Dunes
NASA/JPL-Caltech/UArizona
Well-Speckled Polar Dunes
ESP_025579_2580  Science Theme: Other
These barchan (crescent-shaped) sand dunes are found within the North Polar erg of Mars. This type of dune provides a great record of the wind environment when they formed and moved: barchan dunes’ horns point downwind. Although the question of present-day sand motion is still open, it appears possible that these dunes are active (when not covered in frost) as their crestlines are very sharp and their slipfaces (the inner curved region between the horns/downwind surface) appears very smooth and steep.

In this image, taken during the northern spring season, the dunes and ground are still covered in seasonal frost. The speckled appearance is due to the warming of the area; as the carbon dioxide frost and ice on the dunes warms, small areas warm and sublimate (turn from solid to gas) faster, creating small jets that expose/deposit dark sand and dust onto the surface. Notice that there are no spots on the ground between the dunes. That is because the ground stays more uniformly cold, unlike the darker dune sand.

As spring continues, more spots will appear on the dunes until, suddenly, all of the frost on the dunes and ground will be gone and the dark dune sand will be exposed until next winter.

Written by: Serina Diniega  (22 February 2012)
 
Acquisition date
10 January 2012

Local Mars time
13:57

Latitude (centered)
77.982°

Longitude (East)
115.529°

Spacecraft altitude
317.6 km (197.4 miles)

Original image scale range
63.7 cm/pixel (with 2 x 2 binning) so objects ~191 cm across are resolved

Map projected scale
50 cm/pixel

Map projection
Polarstereographic

Emission angle
5.0°

Phase angle
63.1°

Solar incidence angle
59°, with the Sun about 31° above the horizon

Solar longitude
55.2°, Northern Spring

For non-map projected images
North azimuth:  106°
Sub-solar azimuth:  317.3°
JPEG
Black and white
map projected  non-map

IRB color
map projected  non-map

Merged IRB
map projected

Merged RGB
map projected

RGB color
non-map projected

JP2
Black and white
map-projected   (374MB)

IRB color
map-projected   (208MB)

JP2 EXTRAS
Black and white
map-projected  (213MB)
non-map           (159MB)

IRB color
map projected  (81MB)
non-map           (152MB)

Merged IRB
map projected  (360MB)

Merged RGB
map-projected  (320MB)

RGB color
non map           (135MB)
ADDITIONAL INFORMATION
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products
HiView

NB
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

USAGE POLICY
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/JPL-Caltech/UArizona

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.