Juncture of Two Branches of Dao Vallis
Juncture of Two Branches of Dao Vallis
PSP_002545_1430  Science Theme: Fluvial Processes
Martian outflow channels are believed to be some of the largest features formed from the catastrophic flooding that scoured the landscape during ancient times. The source of the water likely originated in the subsurface and was somehow disturbed, depressurizing an aquifer, causing a sudden burst of water onto the surface.

This image shows multiple branches of the outflow channel Dao Vallis, which flows towards the west (left), ending near Hellas Basin. Although it is not clear exactly where the water that created these floods ended up, it is possible that Dao Vallis and its neighboring outflow channel, Niger Vallis, deposited water in Hellas Basin and formed a short-lived lake.

Within the floor of Dao Vallis is material that appears striped, known as "lineated valley fill." Valley fill material is thought to be ice-rich material that has flowed or been deposited onto the floor. Several lineations or "flow lines" appear to merge towards the upper left of the scene which supports this idea that the fill materials flowed, similar to slow-moving glacial material on Earth.

Also present in this scene is a mantling deposit which drapes much of the mid-latitudes of Mars. The deposit or "mantle" can be seen on south-facing slopes of positive-relief features, appearing as if it's sliding off the walls. The mantle material is thought to be ice-cemented dust that was deposited during times when snowfall occurred on Mars.

HiRISE images, such as this one (see subimage, approximately 680 meters across; 2727 x 1723, 4 MB), show that the mantled unit is textured and full of boulders, which contrasts with the smooth appearance of this material in MOC images.

Written by: Kelly Kolb  (5 July 2007)

This is a stereo pair with PSP_003956_1430.
Acquisition date
10 February 2007

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
256.8 km (159.6 miles)

Original image scale range
26.1 cm/pixel (with 1 x 1 binning) so objects ~78 cm across are resolved

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25 cm/pixel and North is up

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Phase angle

Solar incidence angle
64°, with the Sun about 26° above the horizon

Solar longitude
181.7°, Northern Autumn

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North azimuth:  96°
Sub-solar azimuth:  26.3°
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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/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.