Caves on Mars?
RockDoctor writes "The BBC is reporting that the photo-surveying of Mars has revealed seven suspected cave entrances in the Arsia Mons volcanic area.
This has been hinted at before — long sinuous channels in the same region have been interpreted as collapsed 'lava tube' caves — but the scale of the suggested entrances (sheer drops of 80 to 130m from the surrounding surface) makes my troglodytic hands twitch for my abseiling gear."
Here's the actual article's URL; the also had some supporting papers at LPSC that show up at ADS...
i bcode=2007LPI....38.1371C&db_key=AST&data_type=HTM L&format=&high=44e3b245f913347
;)
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?b
Simon
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Caves can form in rocks other then limestone, such as gypsum - CaSO4.6H2O. In this case water simply dissolves the gypsum, which is slightly soluble in water irrespective of CO2 content. Gypsum is common evaporite mineral on Mars and can form pure deposits e.g. Pollack Crater has gypsum on its floor, it looks like Karst to me.
An extended abstract from the Lunar Planetary Science Conference :
1 .pdf
http://www.lpi.usra.edu/meetings/lpsc2007/pdf/137