At the Confluence of Nirgal and Uzboi Valles
At the Confluence of Nirgal and Uzboi Valles
PSP_003565_1495  Science Theme: Fluvial Processes
This target was suggested by Jonna Sotelo Douglas in Tucson, Arizona. She wrote: “This image is of the confluence of the Nigral and Uzboi Valles and part of the southern rim of Luki crater. The confluence area is marked with dunes, boulders, and other types of sediment formations. As the elevation lowers from the crater wall, the area smoothes out. There are gullies on both sides of the crater wall.”

Nirgal and Uzboi Valles are two valleys to the north of the Argyre impact basin in the southern hemisphere. At this location, the smaller channel, Nirgal Vallis, empties out into the larger Uzboi Vallis.

Most of the features in this image are covered by the dust that is ubiquitous on Mars, hiding the original fluvial features. However, a small patch of resistant outcrop can be observed on the southern side of the crater rim. These appear as white patches that are draped by the darker wind-blown rippled sand. Even the resistant outcrop has been modified by wind, giving it a pockmarked or scalloped texture.

Layering is visible in the resistant outcrops and in the gullied inner wall of the crater. These layers may have been fluvial, volcanic, or aeolian (wind-blown). Given their presence within the valley floor, these may represent some of the sedimentary layers deposited by water when it flowed through the valley.

Written by: Alexandra Davatzas and Jonna Sotelo  (31 October 2007)
Acquisition date
01 May 2007

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
256.5 km (159.4 miles)

Original image scale range
25.9 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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Solar incidence angle
49°, with the Sun about 41° above the horizon

Solar longitude
229.4°, Northern Autumn

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North azimuth:  96°
Sub-solar azimuth:  4.9°
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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.