#1 - Posted: 08/08/2008 08:36
When Phoenix found perchlorate on Mars this week, NASA said the discovery will likely have little bearing on the key question of whether or not Mars might be able to host life. The interesting thing is, the Viking experiment that found life (then didn’t because NASA changed its mind about the criteria for life), was counted out because of a very similar set of circumstances.
The signs of perchlorate were found in two samples of Martian dirt delivered to wet chemistry cells in Phoenix’s Microscopy, Electrochemistry, and Conductivity Analyzer (MECA). But another onboard instrument called TEGA (Thermal Evolved-Gas Analyzer) found no evidence of perchlorates in one soil sample (after finding some evidence in another). The details are here. Basically, the getout is that maybe “some types of perchlorate do not emit chlorine and would thus elude detection by TEGA”.
Really, there’s a lot we still don’t know – including exactly what all the equipment will and won’t detect. Which mirrors Gil Levin’s results that found signs of life on Mars, but were overruled by another (possibly faulty and definitely insensitive) instrument that didn’t. I’m wondering what Gil thinks? I’ll try to find out.