UPDATE: NASA is backing away from this story. See the bottom of the post.
Space.com is reporting that scientists operating earth-based observatories have seeen additional spectral signatures of microbial life on Mars. For some time, several groups have seen methane in the Martian atmosphere, even with fluctuating levels. On Earth methane can be produced by microbes (i.e. cow farts) or by geothermal processes. Since Mars is tectonically dead, the presence of geothermal processes in itself would have been very interesting for life hunters. But, since methane is not unambiguous, the hunt has been on for spectral signatures of a second organic. For a while ethane was the hot ticket.
The recent work-- apparently only submitted so VERY preliminary-- is the result of studying microbial communities in Rio Tinto, Spain, (earth). This region is very acidic and has similarities to the geography observed near the Spirit Mars rover landing site. It you made it very cold and very dry as well, you might have Mars. Space.com is saying that scientists have found microbial life underground at Rio Tinto, which perhaps is releasing some diagnostic compound, which is not made by known geological processes. . I'm guessing it would be sulfur-based.
Wow, I have been popping around technorati. There is a ton of cut-and-paste blogging going on. I got the Space.com report verbatim at least 3 times. A couple of people, including Suicide Girls (I only read it for the articles, honest.) are talking about observations of the mineral jarosite , which is seen on earth near hot springs. Hmm, Suicide Girls and hot tubs? Anyway, According to wiki, this is also old news ("old" meaning 3 months old)
So what exactly is new here? Not sure, except maybe the explicit link to underground living.
UPDATE: Space.com has been contacted by NASA administrators who say that the work in question is not construed as proof of life. I have to say, from what i could gather, it appeared to be an incremental improvement over last year.
Still, this is very important. Proven life on 2 out of 2 known domains of liquid water means you can pretty confidently predict it's also somewhere else. Seeing and characterizing that life can tell you much more about what it takes. At the end of the day, these researchers can piss in a pot and send it to Nature, and it'll get in-- And I'll read it, too.