Pitted Landforms in Southern Hellas Planitia
NASA/JPL/University of Arizona
Pitted Landforms in Southern Hellas Planitia
ESP_038821_1235  Science Theme: 
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This image is of a portion of the Southern plains region within Hellas, the largest impact basin on Mars, with a diameter of about 2300 kilometers (1400 miles).

There are three main phenomena apparent in this image. First, the faint dark streaks that criss-cross the terrain are dust devil tracks that clear the bright dust along their way. Second, the subtle overall bumpy “basketball” texture of the surface is formed by repeated seasonal freezing and thawing of the ice-rich regolith and is common at higher latitudes. Third, the large, elliptical, scalloped depressions are common in permafrost terrains in both hemispheres, where thick, latitude-dependent sedimentary mantles comprise the surface units.

These mantles are composed of ice-rich sediments that degrade as the ice sublimates away and is heated either by the Sun or by locally higher geothermal gradients. Sublimation, or the direct change in phase from ice to gas, occurs on Mars because of its low density atmosphere. These depressions have steeper pole-facing slopes, whereas the equator-facing slopes gently fade into the surrounding terrain. At full resolution (see close up view), numerous sublimation pits and networks of polygonal cracks are visible on the steeper, unstable pole-ward facing slopes.

The overall morphology of this terrain is characteristic of what is called “thermokarstic degradation processes,” which is a term used to describe the formation of pits in an ice-rich terrain due to loss of ice creating pits and collapse features.

Written by: Henrik Hargitai and Ginny Gulick (audio: Tre Gibbs)  (25 March 2015)
 
Acquisition date
07 November 2014

Local Mars time:
15:52

Latitude (centered)
-56.250°

Longitude (East)
74.803°

Spacecraft altitude
249.9 km (156.2 miles)

Original image scale range
50.0 cm/pixel (with 2 x 2 binning) so objects ~150 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection
Equirectangular

Emission angle:
0.3°

Phase angle:
57.0°

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

Solar longitude
229.0°, Northern Autumn

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  23.2°
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map projected  non-map

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JP2 EXTRAS
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non-map           (141MB)


ADDITIONAL INFORMATION
B&W label
EDR products
HiView

NB
Black & white is 5 km across
For scale, use JPEG/JP2 black & white map-projected images
USAGE POLICY
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
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.