Gullies in Winter Shadow
NASA/JPL/University of Arizona
Gullies in Winter Shadow
ESP_049058_2360  Science Theme: Mass Wasting Processes


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This is an odd-looking image. It shows gullies during the winter while entirely in the shadow of the crater wall. Illumination comes only from the winter skylight.

We acquire such images because gullies on Mars actively form in the winter when there is carbon dioxide frost on the ground, so we image them in the winter, even though not well illuminated, to look for signs of activity. The dark streaks might be signs of current activity, removing the frost, but further analysis is needed.

NB: North is down in the cutout, and the terrain slopes towards the bottom of the image.

Written by: Alfred McEwen (audio: Tre Gibbs)  (21 March 2017)
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Acquisition date
13 January 2017

Local Mars time:
13:50

Latitude (centered)
55.805°

Longitude (East)
293.755°

Range to target site
311.3 km (194.6 miles)

Original image scale range
62.3 cm/pixel (with 2 x 2 binning) so objects ~187 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection
Equirectangular

Emission angle:
8.6°

Phase angle:
86.4°

Solar incidence angle
81°, with the Sun about 9° above the horizon

Solar longitude
298.2°, Northern Winter

For non-map projected images
North azimuth:  98°
Sub-solar azimuth:  303.3°
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IRB: infrared-red-blue
RGB: red-green-blue
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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/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.