Gullies in Dao Vallis
Gullies in Dao Vallis
PSP_006659_1460  Science Theme: Fluvial Processes
Gullies on the northwest side of Dao Vallis, a Martian outflow channel, are the focus of this observation. The outflow channels are thought to have been carved by gigantic, ancient floods.

Gullies are largely thought to be the result of water flow, but the origin of the water is much debated. One theory proposes that melting snowpack, or a mantling (blanketing) unit, forms gullies. Such a mantling unit is visible here between some of the gullies, in the full high-resolution image. Some alcove-shaped features appear to have mantling material in them. If the mantling unit is indeed related to gully formation, then gullies are potentially forming here.

Written by: Kelly Kolb  (27 February 2008)
Acquisition date
28 December 2007

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
255.3 km (158.7 miles)

Original image scale range
25.5 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
53°, with the Sun about 37° above the horizon

Solar longitude
9.2°, Northern Spring

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  43.4°
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non-map           (420MB)

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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.