Graben in Memnonia Fossae
Graben in Memnonia Fossae
PSP_005376_1575  Science Theme: Other
The linear depressions that cross this HiRISE image are geological features called "graben." In this part of Mars, graben such as these are collectively named Memnonia Fossae.

Graben can form when the ground is stretched apart due to tectonic forces and can also form when magma is injected underground along long vertical fractures called dikes. The magma forces the dikes open, causing the extension of the ground surface. Both tectonic and dike-related graben are found in Iceland, where tectonic forces both stretch apart the island and enable magmatic dikes to form.

By studying the topography of graben, scientists are able to discern between tectonic and magmatic origins. This part of Mars is especially well suited for this kind of analysis because the ground surface prior to graben formation was relatively flat, making graben-related topography easier to identify and study. Topographic analyses of graben in Memnonia Fossae has revealed that these features formed over magmatic dikes. This means that the Memnonia Fossae are indicators of underground magmatic activity, rather than regional tectonic extension. These kinds of details are key to interpreting the geologic evolution of the surface of Mars.

Written by: ChrisO  (3 October 2007)
Acquisition date
19 September 2007

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
258.5 km (160.7 miles)

Original image scale range
51.7 cm/pixel (with 2 x 2 binning) so objects ~155 cm across are resolved

Map projected scale
50 cm/pixel and North is up

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Emission angle

Phase angle

Solar incidence angle
33°, with the Sun about 57° above the horizon

Solar longitude
316.5°, Northern Winter

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North azimuth:  97°
Sub-solar azimuth:  8.9°
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Black & white is 5 km across; enhanced color about 1 km
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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.