How Microbes Hitchhike From Mars To Earth And Vice Versa

Mars rovers could raise false alarms for astrobiologists eager to find evidence of life. A new study suggests that current techniques for cleaning the equipment could leave some of the hardiest life forms to slip through.

“We might actually select for these organisms. They would be the most likely thing to be able to survive,” Adam Johnson, a graduate student at Indiana University told the journal Icarus. Johnson and his colleagues have subjected Earth’s most resilient life forms to the most extreme environments they could find.

The subjects of the study included bacteria from Siberian permafrost, single-celled microorganisms called haloarchaea from briny saltwater, and yeast-like organisms from cold saline springs in the Canadian arctic.

“We threw a lot of organisms at the experiment,” Johnson said. He and his colleagues then simulated a batch of Martian soil from volcanic basalt rocks. They baked a mixture for 12 hours at 750 degrees Fahrenheit to make sure there was no trace of organic materials. They then mixed the organisms into the soil and let them sit in a glass chamber for a week. When the microbes were buried in just a millimeter of soil, they were able to withstand the ultraviolent radiation exposure on the ‘planet.’

“It seemed to be the actual conditions of the regolith and [the organisms] themselves that determined the chance of survival,” Johnson says. The only organisms that made it were the salt-loving haloarchaea from Mexico and the tardigrades.

“This is the first study where we’ve actually shown that an organism could potentially last for several hundred days on the surface of Mars,” he said.

Keeping Earthly life off of Mars is not our only concern. We also want to keep Earth safe from alien contamination. As head of NASA’s Office of Planetary Protection, Cassie Conley is responsible for ensuring that sample return trips to extraterrestrial environments have a low risk of bringing alien life back to Earth. She also makes sure that Earth life does not hitchhike to potentially hospitable environments.

“If you had pizza last night, or if you put cheese on your salad last night or put cheese on your pasta, you probably have organisms in your mouth right now that could grow on Mars as long as they were protected from (UV) radiation, and they have some level of water and nutrients,” Conley says.

Source: Wired, Vice

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