[meteorite-list] Mars Express Images: Pits and tectonic grabens in Phlegethon Catena

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Feb 15 12:43:57 2006
Message-ID: <200602151742.k1FHgCD02221_at_zagami.jpl.nasa.gov>


Pits and tectonic grabens in Phlegethon Catena
Mars Express
European Space Agency
9 February 2006

These images, taken by the High Resolution Stereo Camera (HRSC) on board
ESA's Mars Express spacecraft, show pits and tectonic "grabens" in the
Phlegethon Catena region of Mars.
[Map showing Phlegethon Catena in context]

The HRSC obtained these images during orbit 1217 with a ground
resolution of approximately 11.9 metres per pixel. The scenes show the
region of Phlegethon Catena, centred at approximately 33.9? South and
253.1? East.

Located south-east of the Alba Patera volcano, Phlegethon Catena is a
region exhibiting a high density of tectonic grabens, which are blocks
of terrain that have dropped relative to their surroundings as a result
of a geological extension of the crust.


[Colour view of Phlegethon Catena]

In the colour image (left), this swarm of grabens trends roughly
north-east to south-west, with individual widths ranging from
approximately one half to ten kilometres.

The series of closely spaced depressions that exhibit a similar
orientation to the grabens is described by the term "catena".

[Black and white nadir view of Phlegethon Catena]

These depressions are rimless, circular to elliptical and range from
roughly 0.3 to 2.3 kilometres across.

The grabens may have formed as the result of stresses associated with
the formation of Alba Patera, which rises three to four kilometres above
the surrounding plains, or the Tharsis rise to the south, which reaches
up to ten kilometres high.


[Perspective view of Phlegethon Catena - looking north]

It is unclear what process is responsible for the chain of depressions.

One possibility is the collapse of the surface due to the removal of
subsurface materials, while other suggestions include that tension
cracks may have formed in the subsurface and caused subsequent collapse.

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 stereo channels.

The 3D anaglyph image was calculated from the nadir and one stereo
channel. Image resolution has been decreased for use on the internet.

[Perspective view of Phlegethon Catena - looking south]
Received on Wed 15 Feb 2006 12:42:11 PM PST

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