Given the response to the last proposal of dak spots indicating life on Mars,

Latest Claims Of Martian Life Are Erroneous Says USGS Scientist
Flagstaff - Sept. 26, 2001
by Timothy N. Titus, Ph.D
U.S.G.S. Astrogeology Team
http://www.spacedaily.com/news/mars-life-01h.html

this is suggested with some trepidation.

However, the images for the recent research on the desert
cyanobacteria able to "follow the water" reminded me of some of the spots seen in the Malin/Edgett gullies.

Desert Bacteria Makes Case for Life on Mars
"The migration of bacteria observed in desert research may hold implications for life in even more severe climates including Mars. Scientists at the Arizona State University have observed and postulated for the first time that bacteria may move with the advance and recession of water rather than sunlight as had been previously believed."
http://www.cosmiverse.com/space09280101.html

Biological Desert Crust
http://lsweb.la.asu.edu/fgarcia-pichel/moab.html

I'm reminded of a MOC image of a south polar pit with gullies:

Evidence for Recent Liquid Water on Mars:
Gullies at 70°S in Polar Pit Walls
MGS MOC Release No. MOC2-237, 22 June 2000
http://www.msss.com/mars_images/moc/june2000/sp_pit/index.html

MOC Image m0302709 - Browse Page
http://ida.wr.usgs.gov/html/m03027/m0302709.html

This image was taken in late winter. However, the site is brightly lit, so perhaps this is already during the time when the Sun is continuously above the horizon at this latitude. Then perhaps the sunlight could have raised the temperatures high enough to allow liquid water. And the cyanobacteria seen in earthly deserts able to
follow the water also show this capability on Mars.
Note that TES measurements show that the temperatures on Mars can reach 0 degrees C even as far south as 70S latitude:

South Polar Cap Recession
http://wwwflag.wr.usgs.gov/USGSFlag/Space/MGS_TES/spole99.html

Also a recent paper showed that above zero temperatures can be reached even on pole-facing slopes at high southern latitudes. See Fig.9 on page 23,169 in "Recent gullies on
Mars and the source of liquid water", by Mellon and Phillips, J. Geophys. Res. 106, 23165, (2001).

A report by members of the TES team was given at this years LPSC conference on these dark spots seen in the gullies:

Title: Ephemeral Dark Spots Associated with Martian Gullies
Authors: Bridges, N. T.; Herkenhoff, K. E.; Titus, T. N.; Kieffer, H. H.
Journal: 32nd Annual Lunar and Planetary Science Conference, March 12-16, 2001, Houston, Texas, abstract no.2126
http://adsabs.harvard.edu/cgi-bin/bib_query?2001LPI....32.2126B

They favor a model of CO2 sublimating leaving dark areas showing underneath as had already been seen on some dunes, but leave open the possibility it could be water ice evaporating:

"Association With Water Ice?
Perhaps gully spots have an origin very different
from seasonal spots elsewhere on Mars,despite their similar
morphology.One speculative explanation is that near-
surface lenses of H2O ice deposited from seepage of water
into the ground following gully formation somehow influ-
ences the formation of seasonal spots.This would both ex-
plain the confinement of spots to the gully channels and the
apparent absence of spots in other high inertia areas of Mars."
EPHEMERAL DARK SPOTS ASSOCIATED WITH MARTIAN GULLIES, p. 2.

Bob Clark