Could New Rover's Wheels Deliver Germs to Mars?

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Could the first terrestrial representatives to land on Mars be of the single-celled, hitch-hiking variety? Although the idea of “infecting” the Red Planet with our germs is nothing new, one microbiologist believes the next Mars rover may have a higher chance of becoming a microbe lifeboat.

Andrew C. Schuerger, of the University of Florida and the Space Life Sciences Lab at NASA’s Kennedy Space Center in Florida, has been carrying out tests on models of the Mars Science Laboratory’s (known as “Curiosity”) wheels and found that the novel (and slightly scary — see why in the video at the end of this article) landing maneuvers of the Mini Cooper-sized rover could increase the chances of contaminating Mars with bacteria than any previous surface mission.

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But don’t get carried away with thoughts that single-celled organisms will set up camp and colonize Mars before we do. Schuerger points out that should any bacteria survive the sterilization processes before Curiosity’s launch and the vacuum (and freezing cold) of space for 10 months, the long-term microbe survival rate is pretty grim. Mars, after all, is humming with radiation and bathed in bacterial-killing ultraviolet light.

“Although this paper suggests we could be transferring bacteria to Martian surface, we don’t know for certain yet,” Schuerger said. “We could very well be losing most due to the exposure to vacuum in space, cosmic rays and hard radiation. Even if cells are present on a rover wheel at launch, they might be dead by the time they get to Mars.”

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But why the concern about Curiosity’s wheels?

Previous Mars rovers (Mars Pathfinder’s “Sojourner” in 1997, and Mars Exploration Rovers “Spirit” and “Opportunity” in 2004) have arrived on the surface using air bags. Once the bags were deflated, and landers righted themselves, the landers opened revealing the rovers on raised platforms.

Sojourner waited on its platform for two Martian days (sols), whereas Spirit and Opportunity sat atop their platforms for 12 and 7 sols, respectively. Only then were the commands sent for the rovers to roll down the ramp and begin getting their tires dusty.

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Curiosity’s landing on the Martian surface will contrast greatly with anything that’s gone before. After entering the Martian atmosphere, parachute jettisoned and heat shield ditched, the large rover requires something more powerful to control its landing. Using the much-discussed “sky crane” — a rocket-powered platform — to lower Curiosity to the ground, the first part of the rover to make contact with the regolith will be its wheels. This is the first time a Mars rover will use its wheels as its landing gear.

And herein lies the problem, says Schuerger.

Soujourner, Spirit and Opportunity’s wheels all had a period of time sitting under the sun, being baked by savage ultraviolet light, before coming into contact with the soil — any surviving bacteria would have been fried. Curiosity’s wheels, on the other hand, will make immediate contact with the soil. Should any hardy bacteria have survived the trip, nestled in the rover’s tread, they could be buried quite nicely into the uppermost layer of Mars regolith.

In fact, according to the study, a contaminated wheel would be quite effective at harvesting bacteria in the Martian regolith. 31.7 percent of the samples delivered into the simulated Mars environment showed growth. Sadly (for the bacteria), their survival rates plummeted soon after — the ultraviolet radiation and high carbon dioxide environment is a huge buzz-kill for microbe development.

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So, there’s a tiny chance that if Earth Brand™ microbes make it past the sterilizing process, if they survive the harshness of the interplanetary environment during transit to Mars, and if they are fortunate to be buried deep enough by the rover’s wheels to be shaded slightly from the sun, then there might be a tiny glimmer of hope that our intrepid single-celled travelers live for more than a few minutes.

But, as pointed out by Astrobiology Magazine, the initial conditions for this experiment are grossly unrealistic: “…the researchers contaminated the rover wheels with perhaps 100,000 times more bacteria compared to what would realistically exist during any of the Mars rover missions. Some Mars rovers get sterilized three or four times, Schuerger said. He added that the journey through space may kill 75 percent of whatever survived after launch.”

Although this work may seem inconsequential when compared with the incredible science that will be done by Curiosity when it lands inside Gale Crater on Aug. 6, 2012, it sure would be a shame if a future headline reads: “Astronauts Discover E. coli In Martian Soil.”

Better to be safe than… a grossly mutated E. coli outbreak in a future Mars habitat greenhouse, I suppose.

SEE ALSO: Are We Infecting Mars With Our Germs?

Source: Astrobiology Magazine

Image: One of Curiosity’s wheels, photographed in April 2011 at NASA’s Jet Propulsion Laboratory. Credit: Ian O’Neill/Discovery News