A new study published online in Journal of Geophysical Research - Planets, concludes that tests conducted by the University of Arizona's Phoenix Mars Lander, show that "soil examined by NASA's Viking Mars landers in 1976 may have contained carbon-based chemical building blocks of life."
A news release from NASA's Jet Propulsion Lab says that "The only organic chemicals identified when the Viking landers heated samples of Martian soil were chloromethane and dichloromethane -- chlorine compounds interpreted at the time as likely contaminants from cleaning fluids. But those chemicals are exactly what the new study found when a little perchlorate -- the surprise finding from Phoenix -- was added to desert soil from Chile containing organics and analyzed in the manner of the Viking tests."