Gullies in Sirenum Fossae
Gullies in Sirenum Fossae
PSP_006695_1415  Science Theme: Fluvial Processes
This image shows parts of Sirenum Fossae that are southwest of Gorgonum Chaos. Some of the troughs (fossae) have gullies on their walls. Gullies are incised slope features that are thought to have formed by liquid water flowing down the slopes.

It is unknown whether the water came from the subsurface or above the surface. The plains around the troughs have a number of mesas and hills that might have formed from erosion of a once-larger rock unit. The bottom of the image shows some dark linear features which are dust devil tracks.

Written by: Kelly Kolb  (26 March 2008)
Acquisition date
31 December 2007

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
253.0 km (157.3 miles)

Original image scale range
25.6 cm/pixel (with 1 x 1 binning) so objects ~77 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
56°, with the Sun about 34° above the horizon

Solar longitude
10.5°, Northern Spring

For non-map projected images
North azimuth:  96°
Sub-solar azimuth:  46.1°
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Black & white is 5 km across; enhanced color about 1 km
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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.