We’re Not Prepared for Contamination Between Worlds

Invasion ecologists make their case for planetary protection needing an upgrade.
We’re Not Prepared for Contamination Between Worlds
Illustration: Angelica Alzona
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The year is 2034.

Humans have sent a probe to Jupiter’s moon Europa to drill through the icy surface and photograph the ocean beneath. In the few hours before it stops functioning, the probe returns images of shapes that could be some form of life. Scientists quickly organize a followup mission that will collect samples of that spot and bring them back to Earth. But, unknown to anyone, the first probe wasn’t sterile—it carried a hardy bacteria that had survived even the mission’s clean rooms. By the time the samples finally reach Earth years later, they’re dominated by this bacteria, which has happily set up shop in Europa’s dark, salty waters. Just like that, our first opportunity to study a truly alien ecosystem has been destroyed.

This is a nightmare scenario for NASA and other space agencies, and it’s one they’ve worked intensely to avoid with every mission to another orb. But some researchers from a lesser-known branch of ecology argue that even the current strict standards aren’t rigorous enough, and as more ambitious missions to other planets and moons get ready to launch, the risk of interplanetary contamination becomes more dire. They say we need to better plan for “forward contamination,” in which our technology disseminates Earth microbes, as well as “back contamination,” in which life from elsewhere hitches a ride to Earth. In fact, we already have a playbook to lean on: the discipline of invasion science, the study of how species on our planet invade each other’s ecosystems.

“What I would say is that, given that there are now concrete plans in place to explore new areas that could have extant life—these pose a new set of risks that were not in play before,” Anthony Ricciardi, a professor of invasion ecology and aquatic ecosystems at McGill University, told Gizmodo. “Invasion science has been applied to biosecurity at national and international levels. My colleagues and I believe that it could similarly guide biosecurity at the planetary or interplanetary scales.”

What are the true chances of an alien invasion? 

Because of the groundbreaking technological advances of recent years, our ability to explore other worlds—from asteroids to planets to ocean moons—is expanding, and so are the risks that come with that. NASA plans to bring bits of Mars to Earth in the early 2030s, and missions to Titan and Europa, which could very well host life, are set to launch this decade.

“It is impossible to quantify the risk because, obviously, we have no data on extraterrestrial contamination,” Ricciardi said. He adds that, without technical analysis, it might even be very difficult to distinguish alien organisms from Earth life.

In 1969, the sci-fi novel and movie The Andromeda Strain detailed what it would be like if a deadly alien microbe slipped onto Earth on a military satellite and the world had to deal with containing it. Although that’s a work of fiction, it’s not so far-fetched: In 2013, researchers described a new bacterial life form sharing less than 95 percent of its genetic sequence with its closest relative, baptized the Tersicoccus phoenicis (something like “cleanroom bug”) after being discovered in NASA and ESA spacecraft clean rooms thousands of miles apart.

Some experts believe in the panspermia theory, the idea that life first appeared elsewhere in the universe and was brought to Earth by crashing meteorites or comets. This could easily work the other way around. We saw a troubling example of this in 2019, when a spacecraft crashed onto the Moon’s surface carrying tardigrades—one of the most indestructible life forms we know of on Earth.

“Risks of disasters such as massive earthquakes or nuclear meltdowns are typically extremely low,” Ricciardi said. “But their occurrence, while highly improbable, is unacceptable, and therefore justifies having safeguards in place for prevention.” That’s how interplanetary microbial contamination should be treated.

How prepared are we for alien invasions?

Space agencies across the world have long been aware of the risks of biological contamination, with planetary protection protocols already being established back in the 1960s. These rules have been updated and tweaked ever since, based on the new endeavors at hand. Some of the rules are: everything should be assembled in sterilized clean rooms; every spacecraft should include an inventory listing all organic matter making it on the trip; the total bioburden—the surface presence of microorganisms—should be below certain thresholds according to the category of the mission; and so forth.

Just in 2020, NASA updated its planetary protection policy for the Moon and Mars. This is a big step because, while exploring Mars was basically prohibited by the old contamination protocol, now the reform supports a human mission to Mars and gives guidelines on how to do so safely.

“If there’s even a very small chance of that happening, we can’t afford it. Because once we are there, you know, we’re screwed, sorry,” Athena Coustenis, chair of the Committee on Space Research (COSPAR), told Gizmodo. Fear is heightened after the coronavirus pandemic, she explained, because it’s shown how unpredictable and challenging containing an unfamiliar microbe can be.

“So we have to be very careful and very cautious in any event,” Coustenis said. “We establish protocols, [and] make them so much more strict, to make them so much more efficient, so that we do not arrive in that situation.”

It’s true, Coustenis noted, that the risk has increased in recent years, especially with private companies getting more involved in space travel. When she joined COSPAR as chair in 2018, the committee met once every two years. Now they meet every two months.

“I’m not going to mention the Tesla that almost hit Mars, and we know that on board, there were some issues with what it was carrying,” Coustenis said. But constantly working toward improvement, as well as getting experts and representatives from every team, private and public, involved in creating the safety protocols, will help mitigate future risks of contamination—be they from science expeditions or cars crashing into planets.

“There are very specific requirements when people are putting missions together, in terms of sterilization of the spacecraft or of the instruments,” Coustenis said. Specifically, creating inventories of all the organic matter on spaceships, so that if forms of life are later discovered on another planet, it is possible to know for as certain as possible that it wasn’t something humans put there in the first place. Although the COSPAR committee is made up of many different scientists who contribute in varied ways, such as biologists, microbiologists, astrobiologists, and geologists, the team is always growing. That might, in the future, mean adding invasion ecologists to the roster.

“We’re going towards a more focused expertise in the committee,” Coustenis said, “to be able to respond, you know, to the needs that are coming up today that are much more serious and much more challenging, I’d say, than what they had before.”

Yet, there are loopholes. In December 2020, a capsule full of samples taken from the asteroid Bennu landed in Australia, and the only rules for its return were that “the probability of the return or returns causing substantial harm to public health... is as low as is reasonably practicable.”

What can invasion science teach us?

Ricciardi and his colleagues recently published a paper in the journal BioScience explaining how invasion science, the emerging field that focuses on ecology, biodiversity, and predator-prey relationships here on Earth, could really come in handy for otherworldly situations.

There’s plenty to learn from because, due to our own human activity, the rate at which “alien” microbes have been spreading in different environments is truly unprecedented. Even the most remote deep ocean or high mountain regions have been affected. Huge numbers of species have gone extinct after the introduction of human-brought invaders like cats and rats.

In their paper, Ricciardi and colleagues reflect on the profound lessons learned and how they can be implemented on a planetary scale.

One of the biggest insights of invasion biology, he said, is that insular ecosystems—places like Hawaii, New Zealand, Australia, and Antarctica that have evolved in almost complete isolation—are especially sensitive to the effects of introduced alien species. Another is that microbes are extremely adaptable. One piece of research showed that the common E.coli bacteria, when left in microgravity conditions in a laboratory, was able to grow over a thousand generations, undergo mutations and evolutions, become more competitive than the average E.coli, and even become antibiotic resistant with the slightest trace of antibiotic in the system.

Right now, biosecurity is often too focused on known threats, according to Ricciardi, who says we need to start venturing toward unknown unknowns.

“Early detection and rapid response are keys to biosecurity,” Ricciardi said.

For example, researchers could look into developing portable, rapid DNA sequencing machines that can be used in space, like the Oxford Nanopore MinION sequencer. And these DNA-sequencing machines should be programmed according to an exhaustive collection of data on any and all microbes that have appeared in clean rooms before, like the Tersicoccus phoenicis.

We should also be doing more scenario planning and horizon scanning, according to Ricciardi, two practices common in the field of invasion science, where lots of data is collected about the relationships between players and fed to supercomputers and given to experts, in order to create forecasts and models of the future.

Of course, all of the above could be aided by including invasion scientists in planetary protection conversations.

“It is more about the process. It’s more about thinking about the issue,” John Wilson, science lead for the South African National Biodiversity Institute’s work on Biological Invasions, told Gizmodo. “It’s about a particular organism reaching a particular place and behaving in a particular way that is managed by the society that’s involved.”

“How invasions progress and how they are dealt with depends on society,” Wilson said. “Invasion biology can actually provide a sort of framework for thinking about how some of those small communities develop.” In fact, he’s been interested in including planetary protection as something to reflect on in the field of invasion science here on Earth. “My gut feeling would be that, geez, I don’t know how we’d deal with new non-Earth-origin-things coming in. There really are many unknown unknowns.”

Although the 2034 Europa tale is invented, there’s plenty of precedent for it. We’ve likely accidentally brought drug-resistant bacteria into the Antarctic ecosystem already, infecting seabirds and seals. Our lack of foresight and carelessness is driving mass extinctions on Earth—are we willing to do the same thing to the next inhabited world we touch?