It appears that this question has been answered. Hidden in the meteorite ALH 84001. You see, ALH 84001 is originally from Mars, spewn out when Mars itself was hit by an interplanetary object. ALH 84001 is not ordinary, though. This discovery confirms what many scientists have theorized.
Life indeed can arise elsewhere.
We are not unique. Paul Davies, a professor of Natural Philosophy, says that life may still exist on Mars deep below the surface. NASA's next mission to Mars, Pathfinder, however won't be able to determine if there is or was life below the Martian surface. This discovery also is strong evidence towards the panspermia theory. Panspermia describes the movement of life between planets via interplanetary objects.