Spaceflightnow is carrying this report on possible signs of life in Martian rock. By studying a meteorite which originated from Mars and was discovered in Egypt in 1911, scientists discovered tiny tunnels which are exact duplicates of those created on earth when bacteria bore through rock. However, unlike samples from terrestrial rock, scientists were not able to extract any DNA from the Martian samples. This could mean there is a way to create these tunnels that does not require a biological agent.

Then again, it very well could be another sign of life on Mars.