Unusual Mound in North Polar Layered Deposits
NASA/JPL/University of Arizona
Unusual Mound in North Polar Layered Deposits
PSP_009855_2625  Science Theme: Polar Geology
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The north polar layered deposits (NPLD) are composed of a stack of ice-rich layers that is up to several kilometers thick. Each layer is thought to contain information about the climate that existed when it was deposited, so the stack of layers within the NPLD may represent a record of how climate has varied on Mars in the recent past.

We can see these internal layers exposed in the many troughs and scarps that have been cut by erosion into the stack. One of these troughs, visible in this image, contains a 500 meter (1640 feet) thick section of this layering.

However, the layers are not the only interesting thing being shown here. There is a conical mound part-way down the slope that is approximately 40 m (130 ft) high. One possible explanation for this anomaly is that it may be the remnant of a buried impact crater that is now being exhumed. As the NPLD accumulated, impacts occurred throughout its surface which were then buried by additional ice. These buried craters are generally inaccessible to us, but in a few rare locations, erosion that forms a trough (like this one) can uncover these buried structures. For reasons that are poorly understood right now, the ice beneath the site of the crater is more resistant to this erosion, so when material is removed in forming the trough the ice beneath the old impact site remains, creating this isolated hill.

An inspection of the full-resolution data shows that polygonal blocks, up to 10 m (33 feet) across, make up this mound. Although covered with reddish dust, the blocks resemble ice-rich blocks seen in other exposures of the NPLD.

Written by: Shane Byrne   (15 October 2008)

This is a stereo pair with PSP_010106_2625.

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Acquisition date
02 September 2008

Local Mars time:
13:37

Latitude (centered)
82.634°

Longitude (East)
265.792°

Range to target site
323.2 km (202.0 miles)

Original image scale range
32.3 cm/pixel (with 1 x 1 binning) so objects ~97 cm across are resolved

Map projected scale
25 cm/pixel

Map projection
Polarstereographic

Emission angle:
9.8°

Phase angle:
70.2°

Solar incidence angle
62°, with the Sun about 28° above the horizon

Solar longitude
121.4°, Northern Summer

North azimuth:
119°

Sub-solar azimuth:
322.8°
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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



Postscript
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. 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. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.