Polar Pit Gullies
NASA/JPL/University of Arizona
Polar Pit Gullies
PSP_005410_1115  Science Theme: Fluvial Processes
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This image shows polar pit gullies in a depression. The gullies do not appear to have been active recently, as their channels and alcoves are covered with polygonal fractures and ripples that have formed over time. The alcoves contain boulders from eroding layers up-slope. Several of the alcoves extend to the slope rim, suggesting head-ward erosion.

The rest of the scene contains abundant polygonal ground, thought to have formed by processes involving ground ice. This image is at a high latitude where polygonal terrain is common. This feature is not found in equatorial regions, which supports a relationship with ground ice because ground ice is not stable near the equator today.

There are several muted circles on the plains in the lower half of the image; these are possibly relaxed craters. If a crater forms in ice-rich ground, the ice enhances the degradation of the crater and gives the crater a “softened” appearance.

Written by: Kelly Kolb  (23 January 2008)
 
Acquisition date
21 September 2007

Local Mars time
14:45

Latitude (centered)
-68.529°

Longitude (East)
1.718°

Spacecraft altitude
252.2 km (156.7 miles)

Original image scale range
25.4 cm/pixel (with 1 x 1 binning) so objects ~76 cm across are resolved

Map projected scale
25 cm/pixel

Map projection
Polarstereographic

Emission angle
5.9°

Phase angle
54.7°

Solar incidence angle
58°, with the Sun about 32° above the horizon

Solar longitude
318.0°, Northern Winter

For non-map projected images
North azimuth:  100°
Sub-solar azimuth:  50.9°
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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/JPL/University of Arizona

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.