[meteorite-list] Mars Express Images: Fractures of Claritas Fossae

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Jan 21 11:38:32 2005
Message-ID: <200501211638.IAA08355_at_zagami.jpl.nasa.gov>

http://www.esa.int/export/SPECIALS/Mars_Express/SEM5K681Y3E_0.html

Fractures of Claritas Fossae
European Space Agency
Mars Express
20 January 2005

These images, taken by the High Resolution Stereo Camera (HRSC) on board
ESA's Mars Express spacecraft, show Claritas Fossae, a series of linear
fractures located in the Tharsis region of Mars.
 
[Image[
Map showing Claritas Fossae in context

The HRSC obtained these images during orbit 563, with a resolution of
approximately 62 metres per pixel. The image shows a region centred
around latitude 25? South and longitude 253? East.

Claritas Fossae is located on the Tharsis rise, south of the three large
volcanoes known as the Tharsis Montes, and extends roughly north to
south for approximately 1800 kilometres. The linear fractures of
Claritas Fossae have widths ranging from a few kilometres to 100
kilometres, and the region is about 150 kilometres wide in the north and
550 kilometres wide in the south.

 
[Image]
Colour view of Claritas Fossae

These fractures are radial to the Tharsis rise, consistent with the idea
that they are the result of enormous stresses associated with formation
of the 8-10 kilometre high Tharsis rise. Faults running east to west are
also visible in the colour image and may have a similar origin.

In the east of the colour image, a prominent linear feature with a dark
shadow is visible. This is most likely a normal fault, the eastern edge
of a 100 kilometre wide "graben". A graben is a block of Mars's crust
which has dropped down due to an extension, or pulling, of the crust.
This graben is characterised by a smooth surface and the difference in
height between the edge of the graben and the plains east of the normal
fault is roughly 2.3 kilometres. Alternatively, this feature may have
resulted from surface collapse due to magma withdrawal.

 
[Image]
Black and white view of Claritas Fossae

The smooth surfaces in the image suggest this terrain has been
resurfaced by lava flows. The observation that the lava flows have
covered some of these faults, particularly in the west and north-east of
the image, suggests that Claritas Fossae is older than the surrounding
terrain.

The outline of a crater with a diameter of 50 kilometres is visible in
the centre of the image. The softened appearance of the crater, and
especially the observation that fractures extend across the crater,
suggest this crater pre-dates the formation of the fractures. South of
this crater, a faint outline is visible with a diameter of 70
kilometres, which may be another ancient crater.

[Image]
Close-up of Claritas Fossae morphology

West of these two craters, there is a small region with an interesting
morphology, shown in the close-up image. These features seem to be
weakly influenced by the north-south fractures. While the cause of
emplacement of this terrain is still unclear, collapse of the surface
due to the removal of subsurface ice might be responsible for these
features.

By supplying new image data for Clarita Fossae, the HRSC camera allows
improved study of the complex geology and history of the area. The
stereo and colour capability of the HRSC camera provides scientists with
the opportunity to better understand the Red Planet's morphology, the
evolution of rocks and landforms, and helps to pave the way for future
Mars missions.


[Image]
Claritas Fossae in 3 D

The colour images were processed using the HRSC nadir (vertical view)
and three colour channels. The perspective views were calculated from
the digital terrain model derived from the stereo channels.

The 3D anaglyph image was created from the nadir channel and one of the
stereo channels. Stereoscopic glasses are needed to view the 3D image.
Image resolution has been decreased for use on the internet.


[Image]
Perspective view of Claritas Fossae, looking south-east.
Received on Fri 21 Jan 2005 11:38:22 AM PST


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