Could life on Earth have originated on Mars? over the past two decades that question has left the pages of science fiction and entered the mainstream of empirical science. Planetary scientists have found that rocks from Mars do make their way to Earth; in fact, we estimate that a ton of Martian material strikes our planet every year. Microorganisms might have come along for the ride. The impacts that launched these rocks into Earth-bound trajectories were violent, high-pressure events, but experiments show that certain species would survive. On passing through Earth’s atmosphere, Martian meteoroids are heated only a few millimeters in from their surfaces, so any microbes deeper inside would not burn up [see “Did Life Come from Another World?” by David Warmflash and Benjamin Weiss; Scientific American, November 2005].
In between takeoff and landing, organisms would need to survive the coast through interplanetary space inside their rocky vessels. Orbital analyses indicate that most Mars meteoroids take thousands or millions of years to get here, but a few (about one in 10 million) arrive within a year or so. Could a bug cling to life for that length of time? The quest for an answer is about to begin.