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Messy humans won't spoil Mars
This week
Jacob Aron
LANDING humans on Mars won’t wreck the search for life on the Red Planet. That’s according to researchers who simulated the impact of a crewed mission to a pristine world by driving across the Canadian Arctic. Space agencies currently take great care to sterilise spacecraft bound for Mars, to avoid contaminating the planet with Earth microbes that could make it harder to find native Martian life. But humans are impossible to
“Humans are impossible to sterilise, so when we go to Mars the contamination risk should be high” sterilise. We are crawling with microbes, inside and out, so when we eventually go to Mars, the risk of contamination will be high. Or at least, that’s what we had assumed. To find out, Andrew Schuerger of the University of Florida in Gainesville and Pascal Lee of the SETI Institute in Mountain View, California, took advantage of an Arctic road trip. During a series of trips between April 2009 and July 2011, Lee was part of a team driving a
specialised vehicle from mainland Canada to the inhospitable Devon Island, the site of a simulated Mars mission. Although the main purpose of the trip was to deliver the vehicle to Devon Island, the team also took the opportunity to simulate the activities of a crewed rover on another planet, with the pristine snow and sea ice they drove over standing in for Mars. During a week-long drive in April 2009 between Kugluktuk and Cambridge Bay, the team made three stops. At each, they took samples from inside the vehicle as well as the surface snow 10 metres away, to see the extent of their microbial footprint. “We had a wonderful opportunity to sample the snow and try to get some measure of how far microorganisms were being dispersed,” says Schuerger. The samples were frozen, then later melted and cultured in the lab to look for bacteria and fungi. It turned out that 85 different microorganisms were found inside the rover, but only one bacterium and one fungus grew in samples from the snow outside (Astrobiology, doi.org/5h5). The pair also found that levels of microbes in the rover declined
David Howells/Corbis
Messy humans won’t spoil Mars
–Make yourself at home–
over time, suggesting the threat of contamination will fall as crewed missions progress. The intense UV radiation on Mars should help to keep things contained, says Schuerger: the vast majority of microbes will be killed after around 15 minutes of exposure. Even fossilised microbes won’t last long enough to be a concern, new research suggests (see “Ancient aliens? Not so fast”, below). “These results are a huge surprise,” says Alberto Fairén of
ancient aliens? not so fast If humans on Mars do shed organic molecules, they won’t be mistaken for traces of extinct Martian life. The harsh radiation on the Red Planet’s surface means that unless alien life went extinct fairly recently, we will have to dig deep to find traces of it. Previously, we thought cosmic rays might take a billion years to destroy biomolecules. But those estimates assumed cosmic rays only did damage by striking them directly. Rays that
14 | NewScientist | 27 June 2015
strike silicate grains or water in the soil can generate free oxygen radicals that also degrade organic molecules, says Alexander Pavlov of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. To see how much damage they do, Pavlov bombarded a mix of amino acids and hydrated silicates with high energy gamma rays in the lab. After a dose equal to about 10 million years of Martian radiation, almost all the
amino acids had broken down, he reported last week at the Astrobiology Science Conference in Chicago, Illinois. That’s good news for astronauts, bad news for alien hunters. To see intact biomolecules, we’d need to find rocks exposed just a few million years ago, or drill at least 2 metres below the planet’s surface – a depth only the ExoMars rover, to launch in 2018, could manage. Bob Holmes
Cornell University in Ithaca, New York. “The theory says that the moment a human sets a foot on Mars, every effort to prevent contamination of the planet would go out the window.” Fairén has previously argued that space agencies are being too cautious when it comes to Mars – sterilisation and other planetary protection for the Viking Mars landers in the 1970s cost $100 million. “A serious rethinking of where time and money are allocated in planetary exploration is clearly in order,” he says. NASA’s planetary protection officer Catharine Conley points out that the methods the pair used wouldn’t necessarily catch all microbes, so contamination could be worse than they measured. The search for life on the Red Planet is so important that extreme caution is a must if we want to find a true Martian microbe, she says. “The more contamination you have, the less easy it is to figure out whether [a Martian microbe] is real.” n
Jacob Aron
LANDING humans on Mars won’t wreck the search for life on the Red Planet. That’s according to researchers who simulated the impact of a crewed mission to a pristine world by driving across the Canadian Arctic. Space agencies currently take great care to sterilise spacecraft bound for Mars, to avoid contaminating the planet with Earth microbes that could make it harder to find native Martian life. But humans are impossible to
“Humans are impossible to sterilise, so when we go to Mars the contamination risk should be high” sterilise. We are crawling with microbes, inside and out, so when we eventually go to Mars, the risk of contamination will be high. Or at least, that’s what we had assumed. To find out, Andrew Schuerger of the University of Florida in Gainesville and Pascal Lee of the SETI Institute in Mountain View, California, took advantage of an Arctic road trip. During a series of trips between April 2009 and July 2011, Lee was part of a team driving a
specialised vehicle from mainland Canada to the inhospitable Devon Island, the site of a simulated Mars mission. Although the main purpose of the trip was to deliver the vehicle to Devon Island, the team also took the opportunity to simulate the activities of a crewed rover on another planet, with the pristine snow and sea ice they drove over standing in for Mars. During a week-long drive in April 2009 between Kugluktuk and Cambridge Bay, the team made three stops. At each, they took samples from inside the vehicle as well as the surface snow 10 metres away, to see the extent of their microbial footprint. “We had a wonderful opportunity to sample the snow and try to get some measure of how far microorganisms were being dispersed,” says Schuerger. The samples were frozen, then later melted and cultured in the lab to look for bacteria and fungi. It turned out that 85 different microorganisms were found inside the rover, but only one bacterium and one fungus grew in samples from the snow outside (Astrobiology, doi.org/5h5). The pair also found that levels of microbes in the rover declined
David Howells/Corbis
Messy humans won’t spoil Mars
–Make yourself at home–
over time, suggesting the threat of contamination will fall as crewed missions progress. The intense UV radiation on Mars should help to keep things contained, says Schuerger: the vast majority of microbes will be killed after around 15 minutes of exposure. Even fossilised microbes won’t last long enough to be a concern, new research suggests (see “Ancient aliens? Not so fast”, below). “These results are a huge surprise,” says Alberto Fairén of
ancient aliens? not so fast If humans on Mars do shed organic molecules, they won’t be mistaken for traces of extinct Martian life. The harsh radiation on the Red Planet’s surface means that unless alien life went extinct fairly recently, we will have to dig deep to find traces of it. Previously, we thought cosmic rays might take a billion years to destroy biomolecules. But those estimates assumed cosmic rays only did damage by striking them directly. Rays that
14 | NewScientist | 27 June 2015
strike silicate grains or water in the soil can generate free oxygen radicals that also degrade organic molecules, says Alexander Pavlov of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. To see how much damage they do, Pavlov bombarded a mix of amino acids and hydrated silicates with high energy gamma rays in the lab. After a dose equal to about 10 million years of Martian radiation, almost all the
amino acids had broken down, he reported last week at the Astrobiology Science Conference in Chicago, Illinois. That’s good news for astronauts, bad news for alien hunters. To see intact biomolecules, we’d need to find rocks exposed just a few million years ago, or drill at least 2 metres below the planet’s surface – a depth only the ExoMars rover, to launch in 2018, could manage. Bob Holmes
Cornell University in Ithaca, New York. “The theory says that the moment a human sets a foot on Mars, every effort to prevent contamination of the planet would go out the window.” Fairén has previously argued that space agencies are being too cautious when it comes to Mars – sterilisation and other planetary protection for the Viking Mars landers in the 1970s cost $100 million. “A serious rethinking of where time and money are allocated in planetary exploration is clearly in order,” he says. NASA’s planetary protection officer Catharine Conley points out that the methods the pair used wouldn’t necessarily catch all microbes, so contamination could be worse than they measured. The search for life on the Red Planet is so important that extreme caution is a must if we want to find a true Martian microbe, she says. “The more contamination you have, the less easy it is to figure out whether [a Martian microbe] is real.” n