Negative and Positive Relief Valley Features
Negative and Positive Relief Valley Features
PSP_005355_2125  Science Theme: Fluvial Processes
How could a valley with flowing water become a high-standing ridge?

When rivers flow, they carry sediment or particles with them. The heavier and larger particles are deposited on the bottom as characteristics of the flow, such as a decrease in speed. The sediments build up and, over time, can fill in a river completely. This would typically occur on a flat plain, so that the filled-in river would be level with the surrounding banks.

As more time passes, wind erosion affects the landscape. The sediment in the valley could be more resistant to erosion, which would allow it to exist while its banks erode.

The sinuous ridge in this image, in eastern Arabia Terra in the Northern Hemisphere, might have been a valley with flowing water in ancient times. At the north (top) end of the image, the ridge transitions to a depression as opposed to being raised. This depression (not imaged by HiRISE) extends into a valley. The Martian valley networks are thought to have formed by flowing water billions of years ago. At the center of the right side of the image there is a branch in the ridge, which supports the valley network theory.

(A sinuous feature is one that winds about in a snake-like pattern, and a ridge is a high-standing feature.)

Written by: Kelly Kolb  (17 October 2007)
Acquisition date
17 September 2007

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
290.4 km (180.5 miles)

Original image scale range
29.1 cm/pixel (with 1 x 1 binning) so objects ~87 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
58°, with the Sun about 32° above the horizon

Solar longitude
315.5°, Northern Winter

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  312.3°
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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/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.