Sinuous Ridge on the Orson Welles Bajada
Sinuous Ridge on the Orson Welles Bajada
ESP_039867_1805  Science Theme: Landscape Evolution
Alluvial fans are piles of debris dumped by rivers when they emerge from the mountains and enter a mostly dry valley. A bajada (such as this example named after the famous American filmmaker) consists of a series of coalescing alluvial fans along a mountain front.

On the surface of this bajada, one can see many sinuous ridges. These ridges mark the path that streams of water took as they flowed into this crater. The sinuosity of the ridges tells us something about the speed of the water flow. Fast moving flows tend to be straighter than slow-moving.

Observations like this help us build a picture of how rivers behaved on ancient Mars.

Written by: HiRISE Science Team (narration: Tre Gibbs)  (22 April 2015)

This is a stereo pair with ESP_032469_1805.
Acquisition date
27 January 2015

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
268.2 km (166.7 miles)

Original image scale range
28.7 cm/pixel (with 1 x 1 binning) so objects ~86 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
48°, with the Sun about 42° above the horizon

Solar longitude
280.4°, Northern Winter

For non-map projected images
North azimuth:  96°
Sub-solar azimuth:  329.4°
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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’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.