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Posted by Robert Clark on September 7, 2007, 10:47 pm
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Polar Pit Gullies (PSP_004988_1085).
"What is particularly interesting about these gullies is that some
might be forming (see subimage, approximately 800 meters across, of
the south-facing gullies in the bottom pit; 1590 x 1445; 7 MB). The
gullies on this wall have incised alcoves, but only a few have well-
developed channels.
"This could be a region of current gully formation. Aiding this
hypothesis is the fact that there are a couple of depressions between
the visible gullies, suggestive of a developing gully where water and/
or material removed from under the surface caused the overlying ground
to collapse. It is also possible that water originating on the surface
is carving out these depressions, although it is difficult to melt
water ice at the temperatures found in this particular location."
http://hirise.lpl.arizona.edu/PSP_004988_1085
Some TES temperature readings of the Mars south polar region show
temperatures might reach the melting point even as far south as this
Hirise image, 71S latitude.
See the images here:
Mars-Ice.org Consortium : All About Ice:
http://www.mars-ice.org/_more/about/sphistory.php
The third image on the 1st row shows south polar temperatures during
Nov 27-29,1999, late southern Spring:
http://www.mars-ice.org/_more/images/vamp0_Nov27-29(Ls=253)Day_Temp(!Uo!NC).gif
The second white circle from the center in this image is at 70S
latitude. Notice that some parts at this latitude are at 0 C
temperature. This was during southern spring. It may be during Summer
the temperatures are even higher.
And an animation showing the temperature change at the south pole
over time on this page also shows some portions at 70S latitude
reached 0 C temperature during November, 1999:
South Polar Cap Recession.
http://www.mars-ice.org/_more/about/sp99.php
http://www.mars-ice.org/_more/images/spole_2pm_1.gif
Bob Clark
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