"Speculation is that already methane is a rather strong indicator life is probably present today on Mars. Just simply based on methane. ...Formaldehyde is destroyed in the Martian atmosphere within 7.5 hours. There is no way that formaldehyde can exist and remain for a long time in the Martian atmosphere. If (formaldehyde) confirmed, possibly life on Mars today, yes." - Vittorio Formisano, Ph.D., Physicist
http://www.earthfiles.com/news/news.cfm?ID=707&category=Science