Why bringing Martian rocks back to Earth is a bad idea

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Michelle D’urbano

AROUND a decade from now, astrobiologists from NASA and the European Space Agency (ESA) will be looking out for a ballistic delivery from the heavens: the first space capsule containing soil and rock samples from the surface of Mars.

Designed to thump into the Utah desert without so much as a parachute to slow it down, that sample return capsule will then be transported to a biosafety level 4 (BSL-4) lab, the highest biological containment set-up available – one used for pathogens like the Ebola virus. Being able, finally, to comprehensively test for signs of life, past or present, on Mars will make those samples a glittering scientific prize: “Returning pristine samples of Mars to Earth has been a goal for generations of planetary scientists,” NASA says.

But the space agencies are letting their quest for answers trump what is safest for life on Earth: no one knows if those samples – to be gathered soon by the Perseverance rover – could contain Martian pathogens to which we would have no defences. Nor do we know if the capsule could break on impact (NASA’s solar wind sampler Genesis was breached when it crashed in Utah in 2004 after its parachute failed), risking contamination of wildlife, rivers, plants and fisheries as well as cities. While BSL-4 labs are highly secure, there have been lapses in the past, with human error usually suspected.

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The risks, though small, are there. Space agencies are working with the US Centers for Disease Control and Prevention in Atlanta and European Centre for Disease Prevention and Control in Sweden to try to mitigate them. But they can’t deny they exist – and that is a problem, because the UN Outer Space Treaty bans contamination of worlds we visit and of Earth on return. Spacefarers, the treaty says, must avoid “adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter”.

At a time when covid-19 is showing the appalling impact of a pandemic, NASA and ESA surely need to change tack. There is a clear new course: bring the samples back for analysis on a lunar orbiting space station, or to a lab on the moon itself, both of which may exist a decade hence.

This is a position supported by the International Committee Against Mars Sample Return (ICAMSR), which highlights Earth return risks. “We support a Mars sample return mission as part of the Lunar Gateway space station, if samples are brought to a specially designed biohazard examination module in lunar orbit, or which is part of a larger lunar base concept as envisioned in NASA’s Artemis programme,” says Barry DiGregorio, director of ICAMSR. “This is the only way to guarantee 100 per cent protection of Earth’s biosphere.”

NASA and ESA say they need to bring samples back to Earth because of the sheer expense and difficulty of operating a complex BSL-4 lab in space, adding that microgravity “would compromise the way we analyse samples”. But that is a problem for the space agencies, not one they can expect the population of Earth to accept unknown risks over.

If the space agencies are serious about a crewed return to the moon as a stepping stone to Mars, they can surely work out how to analyse hazardous samples off-planet. And there is a window in which to do so, too, since the mission to fetch the samples collected by Perseverance isn’t due to lift off for Mars until 2026 – and its design isn’t yet final.

“Leaving the orbital samples in a stable Mars orbit is one of several alternative strategies which are possible after the samples are launched from the Martian surface,” ESA says. The space agencies should do that, and wait until there is a demonstrably safe, off-planet way to analyse them. It will be fascinating to know about life on Mars – but it mustn’t cost us the Earth.

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