Big Fans
NASA/JPL/University of Arizona
Big Fans
ESP_054117_1585  Science Theme: Landscape Evolution
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Alluvial fans are fan-shaped deposits emerging from regions of steep topography. Alluvial fans on Mars are thought to be ancient and record past episodes of flowing water. This image shows part of one of those fans, which has been eroded.

The old stream channels now stand above the rest of the fan as ridges, mostly in the southern (bottom) part of the image. This can occur because the channel materials are more resistant to erosion; perhaps they had larger grains (gravel) or because minerals deposited from the water cemented together.

Written by: Colin Dundas (audio: Tre Gibbs)  (5 March 2018)
 
Acquisition date
11 February 2018

Local Mars time:
15:23

Latitude (centered)
-21.521°

Longitude (East)
66.928°

Spacecraft altitude
261.9 km (163.7 miles)

Original image scale range
52.4 cm/pixel (with 2 x 2 binning) so objects ~157 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection
Equirectangular

Emission angle:
8.4°

Phase angle:
58.8°

Solar incidence angle
65°, with the Sun about 25° above the horizon

Solar longitude
128.0°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  42.8°
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IRB color
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Merged IRB
map projected

Merged RGB
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RGB color
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map-projected   (207MB)

IRB color
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JP2 EXTRAS
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map-projected  (91MB)
non-map           (89MB)

IRB color
map projected  (35MB)
non-map           (126MB)

Merged IRB
map projected  (225MB)

Merged RGB
map-projected  (199MB)

RGB color
non map           (110MB)
ADDITIONAL INFORMATION
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products
HiView

NB
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

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.