[meteorite-list] Traces of the Martian Past in the Terby Crater (Mars Express)

[Ron Baalke]

http://www.esa.int/SPECIALS/Mars_Express/SEMSEWEMKBF_0.html

Traces of the martian past in the Terby crater
European Space Agency
Mars Epxress 
25 January 2008

The High Resolution Stereo Camera (HRSC) on board ESA's Mars Express has
returned striking scenes of the Terby crater on Mars. The region is of
great scientific interest as it holds information on the role of water
in the history of the planet.
 
The image data was obtained on 13 April 2007 during orbit 4199, with a
ground resolution of approximately 13 m/pixel. The Sun illuminates the
scene from the west (from above in the image).  
 
[Terby crater context map]

Terby crater lies at approximately 27 degrees south and 74 degrees east, at the
northern edge of the Hellas Planitia impact basin in the southern
hemisphere of Mars.
 
 
[Terby crater]

The crater, named after the Belgian astronomer Francois J. Terby (1846 –
1911), has a diameter of approximately 170 km. The scene shows a section
of a second impact crater in the north.
 
 
[Terby crater: annotated nadir view, see full caption for details]

Eye-catching finger-shaped plateaux extend in the north-south direction.
They rise up to 2000 m above the surrounding terrain. The relatively old
crater was filled with sediments in the past, which formed plateaux on
erosion.
 
 
[Terby crater, perspective view]

The flanks of the plateaux clearly exhibit layering of
different-coloured material. Differences in colour usually indicate
changes in the composition of the material and such layering is called
"bedding". Bedding structures are typical of sedimentary rock, which has
been deposited either by wind or water. Different rock layers erode
differently, forming terraces.
 
 
[A perspective view of Terby crater]

The valleys exhibit gullies, or channels cut in the ground by running
liquid, mainly in the northern part of the image. These gullies and the
rock-bedding structure indicate that the region has been affected by water.
 
 
[Terby crater, nadir view]

The sediments in this region are interesting to study because they
contain information on the role of water in the history of the planet.
This is one of the reasons why Terby crater was originally short listed
as one of 33 possible landing sites for NASA’s Mars Science Laboratory
mission, planned for launch in 2009.
 
 
[Terby crater, 3D view]

The colour scenes have been derived from the three HRSC colour channels
and the nadir channel. The perspective views have been calculated from
the digital terrain model derived from the HRSC stereo channels. The 3D
anaglyph image was calculated from the nadir channel and one stereo
channel, stereoscopic glasses are required for viewing.