Fans in Fans
Fans in Fans
ESP_020953_0925  Science Theme: Seasonal Processes
This is a sequence of four images acquired in early southern spring over a particular spot in the South polar region. The changes in patterns are so great over just half a season that it is difficult to believe that the images cover the same ground. The cutout helps by focusing on three distinctive fans as they evolve. The dark fans turn into broad bright fans, then new small dark fans form inside the old bright fans. The newer dark fans form along cracks forming polygonal or other patterns.

These changes are driven by sublimation and condensation of volatiles, primarily carbon dioxide. Sunlight passes through the ice to warm subsurface pockets of gas, which escape to form cold jets, and the wind blows to form fans on the surface, depositing dark dust and bright frost. The cutout is from the browse images, reduced in scale about 10x, so these show only approximately one percent of the pixels in the full-resolution images.

Note: The Martian year is measured by 360 degrees of areocentric longitude of the sun or “Ls” (L sub s), where Ls 180-270 marks southern spring and northern fall. The Ls of each image is marked in the subimage and covers only 30 percent of the spring season.

Written by: Alfred McEwen  (16 February 2011)
Acquisition date
15 January 2011

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
247.2 km (153.7 miles)

Original image scale range
24.7 cm/pixel (with 1 x 1 binning) so objects ~74 cm across are resolved

Map projected scale
25 cm/pixel

Map projection

Emission angle

Phase angle

Solar incidence angle
77°, with the Sun about 13° above the horizon

Solar longitude
217.5°, Northern Autumn

For non-map projected images
North azimuth:  235°
Sub-solar azimuth:  34.7°
Black and white
map projected  non-map

IRB color
map projected  non-map

Merged IRB
map projected

Merged RGB
map projected

RGB color
non-map projected

Black and white
map-projected   (524MB)

IRB color
map-projected   (246MB)

Black and white
map-projected  (207MB)
non-map           (376MB)

IRB color
map projected  (73MB)
non-map           (303MB)

Merged IRB
map projected  (142MB)

Merged RGB
map-projected  (131MB)

RGB color
non map           (273MB)
B&W label
Color label
Merged IRB label
Merged RGB label
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/JPL/University of Arizona

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.