Bob Clark wrote:

The link Robert gives for the abstract is:

http://www.marscentral.com/science/mps2000/MPS2000_4095_Annual_CO2_Slab-Ice_Jets.pdf

I think this is the full report given at the conference. It looks like it's incomplete because some references are missing.

Alex writes:

For abstract on the conference site, see
Kieffer, H.H., Annual punctuated CO2 slab-ice and jets on Mars, 2nd International Conference on Mars Polar Science and Exploration, Reykjavik, Abstract #4095, (2000).
http://www.lpi.usra.edu/meetings/polar2000/pdf/4095.pdf

Anyway, as I wrote at http://www.habitablezone.com/space/messages/13126.html

"True, though in all honesty many of the features Greg points to bear little or no resemblance to the 'spiders' that Kieffer presented at the Reykjavik conference, which I had the good fortune to attend. The 'gullies' depicted in MOC NA M09-05128 were obviously formed by a fluid or fluidized debris moving downslope in response to the gravity gradient, which is typified by anastomosis, channel piracy, V-shaped cross sections, etc. In contrast, Kieffer's 'spiders' are usually not found on slopes, and are posited to represent subsurface gas channels serving as conduits for CO2 jets, which may be visible through transparent sections of martian ice. Dust entrained in the flow may be deposited (and shaped by aeolian processes) on the surface when the CO2 breaches through. Unclear, though, are the mechanics for this model. At first glance it would appear that if the separate channels were interconnected, a breach would depressurize the entire system. At any rate, for an example of what Keiffer is actually referring to see:

Lovett, R.A., 'Spiders' Channel Mars Polar Ice Cap, Science 289, 1853 (2000)."

Bob Clark wrote:
One notes the spiders in some case are on raised pedestals. One is reminded of pingo-like structures seen in arctic regions.

Alex writes:
For those who are not familiar with the term, pingos (the singular of which is the Inuit word for "small hill"), are conical shaped ice-cored mounds that can reach up to several hundred meters in diameter and a couple of hundred meters in height. Pingos are found in areas of permafrost, although the term is usually reserved for the features found in the Northwest Territories of Canada, specifically in the Tuktoyaktuk, Mackenzie Delta, and Beaufort Sea regions; however, similar features are
also found throughout the Arctic. I actually travelled to the Canadian NWT and Alaska to study pingos for my masters degree. Pingos are classified as either open-system pingo (hydraulic) or closed-system pingo (hydrostatic) and are formed in lacustrine environments where downward water percolation is inhibited by freezing of the water and lake sediments (caused by the encroachment of the permafrost). The ice expands and forces the overlying tundra upwards to form a dome-shaped hill, similar in morphology to a volcanic cone. At the end stage of the process, fissures or cracks often open up at the summits and allow the ice-cores to partially melt, forming a crater and lake. Interestingly, recent work based on analysis of Viking Orbiter imagery has suggested the possibility of pingos on Mars, namely in Gusev Crater (Cabrol et al., 2000).

References:

N.A. Cabrol et al., Possible Frost Mounds in an Ancient Martian Lake Bed, Icarus 145, 91-107 (2000).

See also http://geonames.nrcan.gc.ca/english/schoolnet/genericterms.html#pingo

Alex R. Blackwell
University of Hawaii