Debris Filled Craters on Mars

by Fraser Cain on March 21, 2006

This photograph was taken by ESA’s Mars Express spacecraft. It shows a mountain in the eastern Hellas Planitia region with craters partly filled with debris. It’s possible that the mountain was covered by glaciers in the past, which filled up the craters with ice and debris; the debris remained after the glaciers retreated. The craters are largely free of meteorite impacts inside, so it’s believed they filled with debris less than a few million years ago.

This video and accompanying images, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, show an unusual flow deposit on the floors of two adjacent impact craters in the eastern Hellas Planitia region, indicating possible glacial processes.

The stereo capability of the HRSC makes it possible to animate 3D anaglyph images, based on digital elevation models. The image data have been acquired during Mars Express orbit 451 from an altitude of 590 kilometres with an original resolution of 29 metres per pixel.

The unusual ‘hourglass’-shaped structure is located in the southern-hemisphere highland terrain of Promethei Terra at the eastern rim of the Hellas Basin, at about latitude 38 South and longitude 104 East.

Most likely the surface morphology is formed by the ‘creep’ of ice and debris, similar to either terrestrial rock glacier landforms or debris covered glaciers which are commonly found in high latitudes and alpine regions.

‘Talus’ material (or ‘scree’, the broken rocks that lie on a steep mountainside or at the base of a cliff) and ice-rich debris accumulated at the base of the remnant massif and filled the upper bowl-shaped impact crater which is approximately nine kilometres wide. The debris-ice mixture then flowed through a breach in the crater rim into a 17-kilometre wide crater, 500 metres below, taking advantage of the downward slope.***image4:left***

Of particular interest is the age of these surfaces, which seem to be fairly intact over a wide area. It has been shown recently that there is some evidence that glaciers were shaping the Martian surface at mid latitudes and even near the equator until a few million years ago.

Typical evidence for a significant loss of volatiles, such as pits and other depressions can be observed on all debris surfaces surrounding the remnant massif.

The statistical analysis of the number of craters formed by meteorite impacts used for age determination also shows that part of the surface with its present-day glacial characteristics was formed only a few million years ago.

Original Source: Mars Express

About 

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

Comments on this entry are closed.

Previous post:

Next post: