OK Jeff,
Here's a tie-in 'on topic' remark about Europa and Mars. Both apparently have magnesium sulfate (MgSO4) on their surface. The suggested common origin of these salt deposits is precipitation from a salty body of water. Fraser Fanale et al. showed in a JGR paper (ca. 2000) that when you leach a stony meteorite with warm distilled water, out comes magnesium sulfate. This finding has important implications for past and present hydrothermal systems, depending on how representative the samples in question are (on Mars, a few rock outcrops, on Europa, the entire surface of the moon). Since we know Mars has volcanoes (just a few, the the biggest known) the finding of magnesium sulfate is obviously not controlling a presence/absence of volcanism and associated hydrothermal activity there (but maybe it is on the latter, on second thought). However, on Europa, if there is an ocean in contact with a seafloor hosting volcanism and associated hydrothermal activity (highly likely underwater), abundant magnesium sulfate signals a problem. On Earth, both magnesium and sulfate are consumed by rock alteration, and consequently are not the dominant ions in ocean water (any more). Logic then suggests either: (1) there is and has been no abundant seafloor hydrothermal activity on Europa (with life implications there); or (2) the Europa starting conditions or history are so unlike Earth that you can indeed have both a MgSO4 ocean and abundant seafloor hydrothermal activity.
It seems the important point I keep missing in Michael's posts on Hoffman and liquid CO2 is that it is indistinguishable in physical effects from liquid water. I agree, but it is very different in chemical effects, with the supporting data on the latter contingent upon how representative the salty rocks are of larger liquid bodies on Mars. This will continue to loom until we get further data. Comparative planetology is what the entire global space programs are about, n'cest pas?
Gary
A gentle reminder that the purpose of this mailing list is the discussion of Europa, not Mars. There are far more appropriate fora for the discussion of Mars-related topics than this mailing list. The relevance of Mars exploration with respect to future missions to Europa would be on topic, but outside of that context is not.
Your anticipated cooperation is greatly appreciated, and will make it easier for me to continue to maintain this mailing list.
Sincerely, Jeff Foust list administrator [EMAIL PROTECTED]
== You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
== You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
