Defrosting Northern Dunes
Defrosting Northern Dunes
PSP_007193_2640  Science Theme: Seasonal Processes
In northern winter a seasonal polar cap composed of carbon dioxide ice (dry ice) forms in the north polar region. This cap covers a vast sea of dunes at high northern latitudes. In the spring the ice sublimates (evaporates directly from ice to gas) and this active process loosens and moves tiny dust particles.

The subimage shows a region of the dunes that are just beginning to lose their seasonal ice cover. In most of the image the dunes are a muted red color. Where the sun is shining on the steep dune crests the frost is gone and dark dust is free to cascade down the sides. This thin layer of dust, like slope streaks found elsewhere on Mars, flows down around obstacles and may come to rest mid-slope.

Written by: Candy Hansen  (12 March 2008)
Acquisition date
07 February 2008

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
317.2 km (197.1 miles)

Original image scale range
31.7 cm/pixel (with 1 x 1 binning) so objects ~95 cm across are resolved

Map projected scale
25 cm/pixel

Map projection

Emission angle

Phase angle

Solar incidence angle
72°, with the Sun about 18° above the horizon

Solar longitude
28.8°, Northern Spring

For non-map projected images
North azimuth:  119°
Sub-solar azimuth:  311.0°
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Merged IRB
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IRB color
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Black and white
map-projected  (444MB)
non-map           (362MB)

IRB color
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non-map           (281MB)

Merged IRB
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Merged RGB
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RGB color
non map           (250MB)
B&W label
Color label
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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.