Re: Water ice in crater at Martian north pole (Forwarded)

Andrew Yee wrote:
> ESA News
> http://www.esa.int
>
> 28 July 2005
>
> Water ice in crater at Martian north pole
>
> These images
> [http://www.esa.int/SPECIALS/Mars_Express/SEMGKA808BE_0.html], 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.
>
> 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 deg North and
> 103 deg 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.
>
> 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).
>
> 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.
>
> 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.
>
> For more information on Mars Express HRSC images, you might like to read
> our updated 'Frequently Asked Questions',
> http://www.esa.int/export/SPECIALS/Mars_Express/SEMJBQXLDMD_0.html
>

This is at 70 degrees North latitude. Temperatures can reach the
melting point of water at 70 degrees South latitude:

South Polar Cap Recession.
http://www.mars-ice.org/sp99.php

But how warm can it get at 70 degrees North latitude?


Bob Clark

.

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