The Changing Ice Cap of Mars
The Changing Ice Cap of Mars
ESP_056563_0960  Science Theme: Seasonal Processes
A story of changes at the South Pole of Mars is told by its icy deposits. Remnants of a formerly more extensive deposit composed of dry ice form what is known as the south polar residual cap. Scientists call it “residual” because it remains after the much larger seasonal cap disappears each summer.

This mesa in this cutout is shrinking over time as the frozen carbon dioxide turns to vapor. Pits in this sheet of dry ice (that give the deposit an appearance resembling Swiss cheese) are enlarging over time, exposing an older surface below that is likely made up of water ice.

In contrast to shrinking ice caps on Earth, climate change is not to blame on Mars. Even as the walls of these pits ablate away the intervening flat surfaces are accumulating new dry ice. The total amount of frozen carbon dioxide at the South Pole may even be increasing.

Written by: Paul Geissler  (26 November 2018)
Acquisition date
20 August 2018

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
244.5 km (152.0 miles)

Original image scale range
49.0 cm/pixel (with 2 x 2 binning) so objects ~147 cm across are resolved

Map projected scale
50 cm/pixel

Map projection

Emission angle

Phase angle

Solar incidence angle
68°, with the Sun about 22° above the horizon

Solar longitude
234.3°, Northern Autumn

For non-map projected images
North azimuth:  115°
Sub-solar azimuth:  39.5°
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IRB color
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Black and white
map-projected  (172MB)
non-map           (187MB)

IRB color
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non-map           (220MB)

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RGB color
non map           (186MB)
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B&W label
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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.