[meteorite-list] Mars Express: 'Hourglass'-Shaped Crater - New Video and Perspectivies

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Mar 20 09:34:43 2006
Message-ID: <200603200223.k2K2Ntq29370_at_zagami.jpl.nasa.gov>

http://www.esa.int/SPECIALS/Mars_Express/SEM618NVGJE_0.html

'Hourglass'-shaped crater - new video and perspectives
Mars Express
European Space Agency
17 March 2006

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.
 
 
[Map showing location of craters in context]

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.

 
[Animated look at the 'hourglass' shaped crater]

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.

 
[Perspective view, looking west of the crater behind the 'hourglass' crater]

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.

The perspective views have been calculated from the digital terrain
model derived from the stereo channels. Image resolution has been
decreased for use on the internet.
Received on Sun 19 Mar 2006 09:23:54 PM PST