[meteorite-list] Mars Express Images: Promethei Terra, southern highlands of Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Oct 13 14:29:56 2004
Message-ID: <200410131829.LAA24511_at_zagami.jpl.nasa.gov>

http://www.esa.int/export/SPECIALS/Mars_Express/SEM95XMKPZD_0.html

Promethei Terra, southern highlands of Mars
European Space Agency
Mars Express
12 October 2004

These images, taken by the High Resolution Stereo Camera (HRSC) on board
ESA's Mars Express spacecraft, show a part of the southern highlands of
Mars, called Promethei Terra.
 
The images were taken during orbit 368 in May 2004 with a ground
resolution of approximately 14 metres per pixel. The displayed region is
centred around longitude 118? East and latitude 42? South.
 
Impact crater - Promethei Terra

They show an area in the Promethei Terra region, east of the Hellas
Planitia impact basin. The smooth surface is caused by a layer of dust
or volcanic ash that is up to several tens of metres thick.

This layer has covered all landforms, and even young impact craters have
lost their contours due to in-fill and collapse of their fragile crater
walls. This layer has been removed by the wind at some ridges and crater
walls.

 
 
Although these images were taken at high resolution and show very fine
detail, this covering layer leads to a slightly fuzzy appearance.
 
 
Close-up of the large impact crater - Promethei Terra

The large impact crater in the southern part of the image is 32
kilometres wide and up to 1200 metres deep. The dark crater floor is
most likely the result of "deflation", the geological term for the
lifting and removal of loose material.

The dust removed here has accumulated in the southern part of the
crater, forming a thick layer. The numerous dark tracks to the
north-western and west are "dust devil" tracks.

 
 
These atmospheric "eddies", like tornadoes on Earth, remove the
uppermost dust layers which have a slightly different colour to the
now-exposed surface. The tracks can be more than 20 kilometres long and
contrast prominently with the lighter-coloured surroundings.
 
 

Craters of Promethei Terra

Dust devil tracks provide short-lived evidence of the ongoing geological
and atmospheric activity on Mars, which consists mainly of the transport
of dust by wind.

Another sign for this "aeolian" (wind-related) activity in the area is
the existence of small dune fields that have formed in some of the
depressions. They can be seen in the crater in the north and in its
surroundings (see close-up).

 
 
Dust devil tracks - PrometheiTerra
 
The dust devils are not limited by geomorphological boundaries: for
example, their tracks cross the crater rim. Dust devil tracks can also
be seen on the thick dust layer in the southern part of the crater.
 
 
Due to the thickness of the dust layer, no darker material is exposed
here. The dust devil tracks show two distinct directions of movement:
east to west and south-east to north-west.
 
 

3D image of the Promethei Terra region
 
The colour images have been processed using the nadir (vertical view)
and three colour channels, and the perspective views have been
calculated from the digital terrain model derived from the stereo
channels. The 3D anaglyph image has been created from the nadir and one
stereo channel.
 
 
Received on Wed 13 Oct 2004 02:29:51 PM PDT