When we envision Martians visiting Earth, the image is usually one of little green men stepping out of a flying saucer and greeting the astonished humans. We don’t usually imagine bacteria from Mars arriving on Earth via meteorite and then over millions of years evolving into humans. But according to Time, that may be exactly what happened all those years ago.
Panspermia is the idea that life on Earth originated outside of the planet, perhaps in the form of bacteria from Mars, or perhaps just raw organic materials from space.
This isn’t as far-fetched as it might sound; space contains many of the ingredients necessary to create life, such as hydrocarbons, water and amino acids. It’s even possible the water on Earth arrived via ice-laden comets.
As far as the possibility of life surviving an interplanetary journey, that too isn’t the stretch it might once have seemed. Bacteria on our own planet have demonstrated the ability to enter states akin to suspended animation in order to survive extreme hot or extreme cold, and at least one species has shown itself resistant to extreme radiation.
Panspermia is not a new idea, and has had its share of controversies. As far back as 1996, scientists at NASA were claiming to have discovered evidence of bacterial fossils on martian meteorites (scientists can tell when a meteorite is from Mars by certain gases trapped inside which match the Martian atmosphere), though the claim was hotly disputed. In 2010, new discoveries were announced in support of the theory.
The latest meteorite to enter the kerfuffle is known as the Tissint meteorite which landed in Tata, Morocco in July 2011. This rocky piece of Martian history is the topic of a paper recently published in Science by Chris Herd, a meteorite expert at the University of Alberta, as well as other researchers.
The scientists’ fear is that any bacteria living on the meteorite at the time of its launch would have been fried before they could get to Earth by processes that melt any open fractures or cavities in the rock — the exact places bacteria would be likely to live.
Despite that all-too-likely possibility, however, researchers like Herd are still enthusiastic and hopeful. While it’s unlikely we’ll unearth any microbial astronauts in the near future, getting closer to the understanding how it might once have happened is a tantalizing journey.