Have We Already Colonized Mars?

There is a small chance that Martian evolutionary history may be confused by the presence of hitchhiking microbes from Earth.

Addressing the insatiable curiosity of its builders, NASA's roving Mars Science Laboratory has taken its first small "roll for mankind" in search of unraveling the clues to the habitability of Mars, past and present.

However, there is a small chance that Martian evolutionary history may be confused by the presence of hitchhiking microbes from Earth.

To date, a total of a dozen U.S., Soviet, and European spacecraft have landed or crashed on Mars. They were all sterilized before leaving Earth, but were the procedures good enough to wipe out every last stowaway Earth bug?

If we were to determine Mars has been biocontaminated by microscopic colonists from Earth, it would open a Pandora's box of astrobiological issues. Did we "play God" by inadvertently seeding another world with life that mutated into a new type of organism that adapted to alien conditions?

There is reason to worry about biocontamation. In 2006 it was reported that a common soil bacterium, called Bacillus, remained healthy and viable on a spacecraft that had been sterilized with ultraviolet light.

Perversely, sending microbes to Mars could become one of the greatest accidental science experiments of all time: the introduction of an organism on another planet that tests the power of Darwinian evolution, and offers a window into Earth's early history.

"We have known from the rock record that complex life is amazingly resilient. Despite repeated near annihilation, complex life has never failed to adapt to new environments. We believe that once life got started on this planet, it survived one way or another," writes Janet Siefert of Rice University in Astrobiology.

The author argues that based on the fossil record it seems inevitable that microbes will eke out a living by beating all odds to accumulate the right genetic material to adapt quickly. But can they pull it off on a dry, irradiated, and hostile place like Mars?

A lab experiment in 2012 subjected microorganisms to Mars-like conditions. The bugs had a rough time coping with a daily thawing and freezing cycle, lack of oxygen, and sparse water. It slowed down their growth and the microbes ultimately perished.

On the other hand say the researchers, even if a small fraction of the stowaways survive on Mars, it's possible that they could rapidly "play the numbers," perhaps like their early Earth ancestors. Relying on quickly trying out a plethora of genetic mutations the bugs might come up with a new survival strategy in short order.

The makeover could be so extreme that it would really be a Genesis II, the origin of a new form of life on another world, say the researchers.

Ironically, I'd say that this line of reasoning leads inevitably to the conclusion that Mars must already be inhabited with native organisms that arose at the same time life appeared on Earth, and were genetically agile at adapting to a dying Red Planet.

Therefore, stranded Earth microbes might compete with Mars microbes for resources. We'd introduce a shadow biosphere on the Red Planet; where completely different form of life co-exists.

Contaminating Mars with Earth organisms, "might not be an experiment we ethically want to conduct, but it would be an unparalleled experimental result," the authors conclude.

Images: Top: E. coli, a hardy bacteria. But is it a potential Mars colonist? Middle: The British Beagle 2 lander that was built to specifically hunt down Mars life. Sadly, it failed. Credit: NASA, ESA