Mystery Mounds in Southern Acidalia Planitia
Mystery Mounds in Southern Acidalia Planitia
PSP_008548_2205  Science Theme: Rocks and Regolith
This image shows bright mounds scattered throughout a rather flat, dark landscape. These mounds range approximately between 20 and 500 meters (yards) in diameter.

The largest among them show central crater-like depressions which give them an appearance similar to terrestrial volcanoes. The origin of these mounds is still unclear. The most widely accepted hypotheses involve extrusion of underlying fluid-like materials (lava, wet/icy sediments) through weak points in the surface.

Similar mounds have been observed elsewhere in the
Northern Lowlands. (The Northern Lowlands encompass a vast region of Mars younger than the rest of the planet, as shown by lower number of impact craters, and well below its average altitude.) Mounds such as the ones shown in this image may hold important clues for scientist to decipher the history of the Northern Lowlands: an old ocean basin? The site of continental-scale volcanism? Detailed analysis of HiRISE and other complementary datasets will help solve this mystery.

Written by: Sara Martinez-Alonso  (2 July 2008)
Acquisition date
23 May 2008

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
301.0 km (187.1 miles)

Original image scale range
30.1 cm/pixel (with 1 x 1 binning) so objects ~90 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
42°, with the Sun about 48° above the horizon

Solar longitude
75.7°, Northern Spring

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  357.6°
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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’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.