[meteorite-list] Mars Express Images: Water Ice in Crater at Martian North Pole

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Jul 28 12:42:33 2005
Message-ID: <200507281641.j6SGfcD07449_at_zagami.jpl.nasa.gov>

http://www.esa.int/SPECIALS/Mars_Express/SEMGKA808BE_0.html

Water ice in crater at Martian north pole
European Space Agency
Mars Express
28 July 2005

[Image]
Perspective view of crater with water ice - looking east
 
These images, taken by the High Resolution Stereo Camera (HRSC) on board
ESA's Mars Express spacecraft, show a patch of water ice sitting on the
floor of an unnamed crater near the Martian north pole.
 
 
[Image]
Map showing crater in context

The HRSC obtained these images during orbit 1343 with a ground
resolution of approximately 15 metres per pixel. The unnamed impact
crater is located on Vastitas Borealis, a broad plain that covers much
of Mars's far northern latitudes, at approximately 70.5? North and 103?
East.

The crater is 35 kilometres wide and has a maximum depth of
approximately 2 kilometres beneath the crater rim. The circular patch of
bright material located at the centre of the crater is residual water ice.

 
 
[Image]
Colour view of crater with water ice

This white patch is present all year round, as the temperature and
pressure are not high enough to allow sublimation of water ice.

It cannot be frozen carbon dioxide since carbon dioxide ice had already
disappeared from the north polar cap at the time the image was taken
(late summer in the Martian northern hemisphere).

 
 
[Image]
Black and white view of crater with water ice

There is a height difference of 200 metres between the crater floor and
the surface of this bright material, which cannot be attributed solely
to water ice.

It is probably mostly due to a large dune field lying beneath this ice
layer. Indeed, some of these dunes are exposed at the easternmost edge
of the ice.

Faint traces of water ice are also visible along the rim of the crater
and on the crater walls. The absence of ice along the north-west rim and
walls may occur because this area receives more sunlight due to the
Sun's orientation, as highlighted in the perspective view.

 
[Image]
3D anaglyph view of crater with water ice
 
 
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 images were created from the nadir channel and one of
the stereo channels. Stereoscopic glasses are needed to view the 3D
images Image resolution has been decreased for use on the internet.
Received on Thu 28 Jul 2005 12:41:37 PM PDT