Field of Fans
NASA/JPL/University of Arizona
Field of Fans
PSP_002532_0935  Science Theme: Seasonal Processes
This caption is part of a December 2007 AGU presentation "Spring at the South Pole of Mars."

At the very beginning of spring in the southern hemisphere on Mars the ground is covered with a seasonal layer of carbon dioxide ice. In this image there are two lanes of undisturbed ice bordered by two lanes peppered with fans of dark dust.

When we zoom in to the subimage, the fans are seen to be pointed in the same direction, dust carried along by the prevailing wind. The fans seem to emanate from spider-like features.

The second subimage zooms in to full HiRISE resolution to reveal the nature of the "spiders." The arms are channels carved in the surface, blanketed by the seasonl carbon dioxide ice. The seasonal ice, warmed from below, evaporates and the gas is carried along the channels. Wherever a weak spot is found the gas vents to the top of the seasonal ice, carrying along dust from below.

The anaglyph of this spider shows that these channels are deep, deepening and widening as they converge. Spiders like this are often draped over the local topography and often channels get larger as they go uphill. This is consistent with a gas eroding the channels.

A different channel morphology is apparent in the lanes not showing fans. In these regions the channels are dense, more like lace, and are not radially organized. The third subimage shows an example of "lace."

Written by: Candy Hansen  (12 December 2007)

This is a stereo pair with PSP_002533_0935.

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Acquisition date
09 February 2007

Local Mars time:
16:27

Latitude (centered)
-86.400°

Longitude (East)
99.016°

Range to target site
276.2 km (172.6 miles)

Original image scale range
55.3 cm/pixel (with 2 x 2 binning) so objects ~166 cm across are resolved

Map projected scale
50 cm/pixel

Map projection
Polarstereographic

Emission angle:
27.5°

Phase angle:
110.5°

Solar incidence angle
88°, with the Sun about 2° above the horizon

Solar longitude
181.1°, Northern Autumn

North azimuth:
100°

Sub-solar azimuth:
37.4°
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Postscript
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. 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. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.