Seasonal Changes of Polar Megadunes
Seasonal Changes of Polar Megadunes
ESP_069261_2620  Science Theme: Aeolian Processes
This image covers a unique polar dune field during northern spring, revealing some interesting patterns.

The main “megadune” formation comprises giant crescent-shaped dunes called “barchans,” which have been migrating (from upper-right to lower-left) over the past several centuries or more.

Light-toned seasonal carbon dioxide frost and ice that accumulated over the winter still covers the majority of the surface, and is now starting to defrost and sublimate in complex patterns. (This depends on the slope aspect and incoming solar illumination). As frost is removed, the darker “coal-black” nature of the dune sand is revealed. For example, compare with this image taken in summer, when frost is gone and the dunes are migrating.

The striped patterns of the carbon dioxide frost and linear nature of the dune field give it a sea serpent-like appearance.

Written by: Matthew Chojnacki (narration: Tre Gibbs)  (14 July 2021)
Acquisition date
06 May 2021

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
317.3 km (197.2 miles)

Original image scale range
31.8 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
67°, with the Sun about 23° above the horizon

Solar longitude
41.3°, Northern Spring

For non-map projected images
North azimuth:  112°
Sub-solar azimuth:  322.5°
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Black & white is 5 km across; enhanced color about 1 km
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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.