The following is an extract from our Lost in Space-Time newsletter. Each month, we hand over the keyboard to a physicist or two to tell you about fascinating ideas from their corner of the universe. You can sign up for Lost in Space-Time for free here.
When astronauts on the Apollo 11, 12 and 14 missions returned to Earth, they were for three weeks – along with the lunar samples they’d collected – to make sure they hadn’t brought any potentially deadly microbes back from space. (Apollo 13 never made it to the moon, so as a silver lining, they got to skip quarantine). Even at the time, scientists were fairly certain that the threat of a lunar plague was extremely unlikely, but they decided to err on the side of caution until more research could confirm that the celebrated Apollo missions wouldn’t lead to “Alien Flu from Outer Space!” headlines.
Now that we’ve studied the surfaces and habitability of the moon and Mars for a few more decades, we’re not as worried about the contamination of Earth by lunar or Martian germs. Instead, our concern is focused on the other direction: how do we protect space environments from Earth life?
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The parts of the solar system that we’ve explored so far are extremely unwelcoming to life, but we already know of terrestrial organisms, often called “extremophiles”, that can thrive in harsh environments like highly acidic volcanic springs, the ice of Antarctica and the deepest parts of the ocean floor. If some of these extremophiles hitched a ride to another planet on a lander or an astronaut’s spacesuit, they might find a way to survive and even evolve to thrive in their new home before we knew what was happening. When this scenario was discussed during the early days of space exploration in the 1950s, biologists expressed concerns that by the time we began to search for extraterrestrial life in space environments, we’d find that it was already there – brought along from Earth on our spacecraft. In other words, accidental (or intentional) contamination could threaten the integrity of future astrobiological research sites.
So how can we keep from becoming Space Invaders? A good place to start is the of 1967, the cold war-era international agreement that covers human activity in space, forbidding the use of things like nuclear weapons and clarifying who is liable if a spacecraft crashes into your property and causes damage (answer: the country that launched the spacecraft). The treaty requires that we avoid the “harmful contamination” of celestial bodies like the moon and Mars. But even before this was codified into international law, the International Council for Scientific Unions’ Committee on Space Research (COSPAR) began providing in 1959 for preventing contamination during space missions. These “planetary protection” guidelines have been continually updated in the decades since as our technologies, and our understanding of the planets and moons of the solar system, improved.
COSPAR categorises destinations in space based on their vulnerability for contamination and suggests different procedures for each category. For example, a mission to Mercury requires no planetary protection efforts, due to Mercury’s obvious past and present uninhabitability, while a trip to Venus or the moon has only a “remote chance” of contaminating future scientific studies there, and merely requires some pre- and post-mission documentation. However, a mission to a planet or moon vulnerable to “significant contamination” of its habitable regions must include extra precautions: the spacecraft should be constructed in a clean room, for example, and if the craft will actually touch down on the surface of another world, it may need to be sterilised prior to launch.
Problem solved, right? We can just follow the COSPAR guidelines, and outer space will be safe from our biosphere? Not quite. For one thing, no sterilisation procedure is able to completely eradicate all chance of contamination. And within the scientific community, there is a tug of war between the chance to improve our astrobiological observations in space and the possibility of contaminating the very environment we’re trying to study. For example, how could we drill through the ice covering Jupiter’s moon Europa to search for life in its suspected subsurface ocean without possibly introducing terrestrial microbes?
But the broader challenge is that the scientific community is not the only group of humans interested in sending human technology into space these days. Private space companies hoping to profit off space tourism or mining are motivated by their obligations to their shareholders, not by future astrobiological research, so it will be tempting for them to cut corners on expensive or slow procedures like sterilising equipment or documenting organic payloads.
And this isn’t just hypothetical speculation. In 2019, the Israeli space company SpaceIL attempted to land the first privately funded spacecraft on the moon. The lander, called Beresheet, was carrying a digital library created by the Arch Mission Foundation, a US nonprofit hoping to create an off-world backup of human civilisation. But Beresheet , scattering its payload – including the Arch Mission Foundation’s library – across the landing site. Only after the crash did the Arch Mission Foundation reveal that they had added several thousand tardigrades to the library. Also known as water bears, tardigrades are extremophile microorganisms that can survive exposure to the vacuum, cold and radiation of space.
Even if the tardigrades survived the crash, they likely remained in the dormant state they use to survive extreme environments, and there is nowhere on the moon where they could rehydrate and begin to reproduce. This is exactly why spacecraft headed for the moon are not required to be sterilised by COSPAR’s planetary protection policy. On the other hand, COSPAR does recommend that mission planners document an inventory of all organic materials present on a lander bound for the moon. The Arch Mission Foundation flouted this policy, according to cofounder Nova Spivack, by smuggling dormant tardigrades into the library aboard the Beresheet without informing SpaceIL. “Space agencies don’t like last-minute changes,” Spivack said . “So we just decided to take the risk.”
Beyond the risk of smuggled tardigrades, the planetary protection problem gets even more complicated when astronauts are included on a mission. Humans can’t be sterilised; not only would most techniques used for sterilising spacecraft kill a human astronaut, but we now know that a healthy human body depends on a complex microbiome of bacteria and other organisms. This problem will worsen as humans move toward permanent habitation in space. How can we grow crops, process waste and raise children without exposing the surrounding environment to our microbiomes?
The Arch Mission Foundation’s approach of asking forgiveness rather than permission will be a tempting strategy for future private space companies hoping to avoid the financial cost of following planetary protection rules or space settlers actively attempting to create new ecosystems away from Earth. They will find allies in space settlement advocates like author and engineer Robert Zubrin, who bristles at the very existence of planetary protection regulations as an overreach by scientists: “It’s not just a matter of who gave the Moon to astrobiologists, but also of who gave the universe to professional scientists. Humans do not exist to serve scientific research. Scientific research exists to serve humanity,” . As space continues to fill with people who prioritise profit or colonisation over scientific exploration, our window to detect potential life in the solar system without terrestrial contamination is likely closing.
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