Mars is no stranger to life. Seven US spacecraft have successfully landed there and all of them took microbes to the planet’s surface (though the bugs probably did not survive for long). Yet the world’s space agencies continue to maintain strict spacecraft sterilisation procedures in the hope of minimising the spread of Earth life beyond our planet.
For decades this ethos – known as planetary protection – prevailed. Now, some scientists say, these precautions are undermining the search for life beyond Earth by raising costs and inhibiting innovative missions without meaningful benefits.
Of all missions to Mars to date, only the Vikings, the first trips to the Red Planet, were intended explicitly to test for life. Spacecraft that went later did not have that ability. But a future mission will, and, the protectionist thinking goes, a rover might not be able to distinguish between a life form native to Mars and one with origins on Earth. In July 2013, astrobiologists Dirk Schulze- Makuch and Alberto Fairén disputed this in Nature Geoscience.
“If Earth micro-organisms can thrive on Mars, they almost certainly already do,” the authors write. “If they cannot, the transfer of Earth life to Mars should be of no concern, as it would simply not survive.”
With clear evidence of a watery history and some signs of water present, Mars could be where we find life in our solar system. And with the development of Curiosity’s precise landing system, we can finally reach the intriguing parts of the planet. But it’s these areas that require a craft sterilisation process.
In the 1970s, Vikings 1 and 2 revealed what seemed like a dead planet, so planetary protection requirements were relaxed. Now, with a more nuanced understanding of Mars’ environment, missions set to visit areas with evidence of flowing water below the surface have to meet the rigorous – and more costly – Vikings standards. “In practice, everyone kind of avoids [these areas] because it really increases the price tag on the mission,” Schulze-Makuch says.
The cost increase is generally said to be around 10 per cent, but Cassie Conley, Nasa’s planetary protection officer, says this is not accurate; the number is closer to 4 per cent of Curiosity’s R25 billion budget.
Planetary protection is a game of risk assessment, she says, and it just makes good sense. “You’d think they’d want to protect their ability to do their science without contamination,” Conley says. “It’d be like trying to study bacteria in the lab and spitting on your petri dish.”
But Conley’s concerns over false positives might just be a red herring. According to Schulze-Makuch, the dissimilarities in the two planets’ environments surely would have led to the evolution of distinguishable differences.
Finally, there’s the philosophical conundrum of what responsibility, if any, we have to other planets and any life we leave there. The truth is, we’re never going to be able to fully protect Mars if we intend to explore it. And spreading is simply what life does.
“If we want to survive for a long time, we have to expand beyond Earth,” Schulze-Makuch says. “There’s no other way.”
– By Laura Dattaro