Our search for alien life is getting serious. With better telescopes and a growing scientific consensus that we’re probably not alone in the universe, we’re beginning to look farther and wider across the vastness of space for evidence of extraterrestrials.
But it’s possible we’re looking for too few signs in too few places. Having evolved on Earth, surrounded by Earth life, we assume alien life would look and behave like terrestrial life.
What if we’re wrong? What if E.T. is out there waiting to be discovered by the first astronomer willing to open their mind to the possibility that, to us, alien life might seem really weird?
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Some scientists are trying to fix our Earth bias. In a new study that was made available to read on July 27, a team led by Arwen Nicholson, an astrophysicist at the University of Exeter, attacked one assumption that’s widespread in astronomy. There’s a common line of thought that a distant “exoplanet”—a planet outside the solar system—would need a certain amount of oxygen and hydrogen to support life. And those lifeforms, as they lived and died and evolved, would excrete methane gas that would build up in the atmosphere.
Methane is one of the big things astronomers look for when it comes to evidence of alien life. They call it a “biosignature.” But with over 5,000 thousand confirmed exoplanets on the official roster and only so many telescopes that are powerful enough to survey them, astronomers tend to exclude planets that appear to be nutrient-poor—lacking, say, the concentration of hydrogen that we have here on Earth.
To scrutinize that assumption, Nicholson and her team built a sophisticated computer model of a roughly Earth-like planet, populated it with simple simulated microbes then started taking out hydrogen. The goal: to see whether the microbes would survive, and whether they’d still excrete detectable levels of methane as they struggled on their resource-poor planet.
Surprise! The tough little organisms hung on. And yes, they still pooped out enough methane to register in astronomical surveys from light-years away. “These results help deepen our understanding of life-planet interactions,” Nicholson and her co-authors wrote. “It reduces the need to make unnecessary assumptions about alien life based on life on Earth.”
In practical terms, Nicholson’s study—which has been peer-reviewed and accepted for publication in the Monthly Notices of the Royal Astronomical Society—could expand the list of exoplanets that scientists consider worth surveying for signs of life.
Astronomers are lining up to take turns to use NASA’s new James Webb Space Telescope to inspect planets for biosignatures. The priority, in this first year of JWST’s operations, is the seven possible Earth-size planets in the TRAPPIST-1 star system, 40 light-years from Earth.
TRAPPIST-1’s planets are pretty far away; it’s not as if we’d have a real chance to visit any potential life on these worlds any time soon. Astronomers are targeting them anyway, rather than closer but seemingly more barren planets, because the TRAPPIST planets seem likelier to have all those nutrients Earth life really favors. “Would you prefer relatively poor data on a hard-to-observe, but really Earth-like, world—or much better data on a nearby nutrient-poor planet?” is how Étienne Artigau, a Université de Montréal astrophysicist who wasn’t involved in Nicholson’s study, described the surveyors’ dilemma.
If Nicholson’s model gains traction, however, astronomers might be willing to risk their precious telescope time on a closer planet that has thus far seemed a bit hostile to life.
But the study by Nicholson and her co-authors is still just a nudge toward a more open-minded approach to the search for E.T. She and her team are still assuming aliens would share the same basic metabolism that’s common on Earth. Take in oxygen and hydrogen, and excrete methane. “As we only know of life on Earth it's hard to not be swayed by it,” Nicholson conceded.
But we can at least imagine lifeforms with totally different metabolisms. “For planets that might be very different [from] our own, different metabolisms could be possible than those on Earth,” Nicholson said. “Identifying those possible metabolisms will be key for contemplating life on distant planets.”
The problem is that, unless and until we discover some lifeform with a radically different metabolism, it’s unlikely any serious scientist is going to create survey methods specifically tailored for finding signs of that kind of life. It’s a chicken-and-the-egg sort of problem—you can’t search for a thing you don’t know you’re looking for. And few scientists seem eager to design surveys around what are, at present, fictional forms of life.
“We are always limited by our imagination, which is guided by our experience,” Avi Loeb, a Harvard physicist who also wasn’t involved in Nicholson’s study, told The Daily Beast. For all their intelligence, curiosity and training, scientists tend to be extremely conservative when it comes to weird stuff.
It’s that reluctance to probe the totally unknown that keeps our search for alien life so closely tethered to our understanding of Earth life. The same institutional conservatism could keep us from recognizing aliens even after we’ve found them.
Take ‘Oumuamua. That’s the name astronomers gave to a very odd oblong object, up to 3,000 feet long and shiny, that hurtled through our solar system back in 2017. No one knows for sure what it was. Likewise, no one should say for sure what it wasn’t. But despite ‘Oumuamua behaving like we’d expect an alien spacecraft to behave, very few scientists—Loeb is one of them—are urging their colleagues to at least consider the possibility that the strange object was an opportunity for first contact.
Instead, the scientific community just sort of shrugged as ‘Oumuamua speeded away. And that’s a problem, Loeb said. “Reality has ways of surprising us, so we should simply search for things or behaviors that are not familiar to us.” When a mysterious object zooms through the solar system, defying easy categorization, maybe worry less about the categories. Investigate with an open mind.
The same goes for planetary surveys. To boost our chances of finding alien life, we could look in places we wouldn’t normally expect life to thrive. It’s a big universe, after all. And it only seems stranger by the day as our discoveries pile up.
More and more scientists are coming around to the idea that aliens are out there, somewhere. Maybe more scientists need to also come around to the idea that those aliens might be really weird.
