Saturday, April 14, 2012

Life on Mars After All?

What are the odds I'd regret skipping statistics sooner or later...

This has been covered pretty well in the various science blogs, but I find it fascinating.

Back in the middle 1970s Americans (okay, some Americans) followed the Viking 1 and Viking 2 robot spacecraft which landed on Mars in 1976.  We nerds were enthralled to hear that a test for biological processes tested "positive" in each of the landers' chemistry labs.  Reality intervened in short order as mission scientists and researcher in the field coalesced around a consensus that the positive result probably resulted from a chemical reaction that had nothing to do with the presence of life on the red planet.  Oh well, we'd have to wait for a manned mission, which us space junkies assumed would occur sometime in the early 1980s.  Hmmn.

Fast forward nearly four decades.  Plenty of neat rovers and an awesome Mars Reconnaissance Orbiter, but still no manned mission to Mars, or even a sample return mission.  Then some scientists took another look at the Viking Program data using advanced statistical techniques.  You know, the usual, "deep analysis of data structure along continua including signal vs. noise, entropy vs. negentropy, periodicity vs. aperiodicity, order vs. disorder using LZ complexity, Hurst exponents, Lyapunov exponents, Brock-Dechert-Scheinkman statistics, fractional correlation dimensions, etc."

In their paper Complexity Analysis of the Viking Labeled Release Experiments researchers Giorgio Bianciardi, Joseph D. Miller, Patricia Ann Straat, and Gilbert V. Levin argue, "if the LR gas evolution in the active experiments were entirely non-biological, it would sort with the other purely physical, rather than biological processes. In actuality, LR gas evolution in the active experiments sorted with the biological measures, while gas evolution controls (e.g. heat-sterilized) sorted with non-biological measures.  We believe that these results provide considerable support for the conclusion that the Viking LR experiments did, indeed, detect extant microbial life on Mars."

Well, it's not a manned mission, or even a sample return mission, but it's pretty cool.  Too bad there's no clue as to when we'll be visiting in person...