re: CO2-water clathrates to explain the Martian spiders.
On uplink.space.com, Alex Blackwell provided a link to a paper that argues that the spiders are due to liquid water brines:
Astrobiology
Spiders: Water-Driven Erosive Structures in the Southern Hemisphere of Mars
Aug 2006, Vol. 6, No. 4: 651-667
http://www.liebertonline.com/doi/abs/10.1089/ast.2006.6.651
It's available for free download. It's a large file so you should download it rather than opening it in a window.
Bob Clark
