They haven't yet figured out how to draw blood from stones, but a group of French researchers is offering new insight that could change how scientists search for signs of life in Martian rocks.
By studying the laboratory fossilization of microorganisms, scientists have caught a glimpse into how early Earth and potential Martian life might be preserved in rocks. The scientists focused on Pyrococcus abyssi and Methanocaldococcus jannaschii, extremophiles which thrive in piping hot (up to 176°F), oxygen-lacking (<0.2% of current levels) environments.
Some believe this sort of hot, anoxic environment is where life may have originated on Earth, and perhaps even on Mars.
More: http://www.space.com/scienceastronomy/091001-AM-fossils-mars.html (http://www.space.com/scienceastronomy/091001-AM-fossils-mars.html)