Experiment Shows Some Life Can Survive in Exoplanet-Like Conditions

Artist’s illustration of a rocky exoplanet
Artist’s illustration of a rocky exoplanet
Illustration: NASA/JPL-Caltech/R. Hurt (IPAC

Single-celled organisms like Escherichia coli and yeast can grow and survive in an atmosphere like the kind theorized to exist on many rocky exoplanets, according to a new paper.


Scientists would love to know whether there’s life elsewhere in the universe, and part of answering that question is determining what an inhabited exoplanet would look like to our telescopes here on Earth. Do these planets have atmospheres like ours? How would the presence of life change these atmospheres? If life can survive in a hydrogen-rich atmosphere like the kind expected to be found on many exoplanets, then scientists may need to broaden their definition of what a life-supporting planet might look like.

“This should open up—continue to push—astronomers on what kinds of planets might be habitable,” the study’s first author and MIT professor Sara Seager told Gizmodo in an email. “We will have so few planets to search for life around, even with our upcoming sophisticated telescopes, that we want to keep options open.”

The team of MIT researchers kicked off colonies of the E. coli bacteria and brewer’s yeast. They incubated the microorganisms in four bottles with different gas concentrations: one with regular air, one with 100 percent hydrogen, one with 100 percent helium, and one with 20 percent carbon dioxide and 80 percent nitrogen. The microorganisms were able to reproduce in all four bottles, but they did so at least twice as quickly in the air than in the other gases, according to the paper published in Nature Astronomy.

It’s no surprise that a microorganism can survive without oxygen—there are plenty of so-called anaerobic organisms living here on Earth. Some microorganisms can survive in the planet’s most extreme environments, such as around deep-sea hydrothermal vents. But, the researchers explain, if microbes can survive a 100 percent hydrogen environment, then they can survive the atmospheres most likely to be found on rocky exoplanets.

Astronomers have yet to observe a rocky exoplanet with a hydrogen atmosphere, but they believe that rocky planets with hydrogen atmospheres would be easier to spot and study than those with atmospheres of heavier gases like carbon dioxide and nitrogen. They’re pretty sure that they will be able to see these planets and determine the composition of their atmospheres with upcoming telescopes, including the James Webb Space Telescope. Maybe, based on this most recent study, scientists will be able to see signs of life in these hydrogen-dominated exoplanets, in the form of trace gases emitted by microorganisms.


This doesn’t mean that life definitely exists on such planets, and lab experiments don’t exactly recreate what happens in nature. These E. coli and yeast cells started their lives (and evolved) in Earth’s nitrogen- and oxygen-rich atmosphere. And the conditions in the lab aren’t the same as those on an exoplanet. Actual exoplanet atmospheres would contain a mix of gases due to the chemistry on their surface. In order to maintain a hydrogen-only atmosphere, these exoplanets would either have to be colder than Earth, have stronger gravity at their surface, or have a way to replenish the hydrogen in their atmosphere—and it’s hard to say what effects any of these changes would have on life.

But this study still offers the hope that life could be more diverse than what we see on Earth, and if so, then maybe the next round of telescopes will be able to find it.


Former Gizmodo physics writer and founder of Birdmodo, now a science communicator specializing in quantum computing and birds


C.M. Allen

It’s not a question of being able to survive in extreme conditions. Given enough time and the right pressures, evolution can stumble into some incredible capabilities — we can see that all around us, right here on Earth. No, the question is if life can form under those conditions. If it can’t form in the first place, no measure of evolutionary capabilities will ever be relevant. Life that does not and cannot form does not evolve either, no matter how ideal the conditions might seem. After all, life did not start under the present day conditions on Earth. Not even close. It evolved to live in these conditions (and killed off a lot of lifeforms getting here, too).

And therein lies the billion year question — what exactly were those conditions that gave rise to the first simple lifeforms on Earth? How important is water? Solar energy? Geothermal energy? Chemical energy? Atmospheric conditions and composition? We don’t have enough laboratories to even begin testing the most minimal of possible combinations, let alone enough of them to create a reasonable sample size to answer with any sort of certainty. And we definitely don’t have the time, given the scales at which these sorts of processes unfold. Life itself is an ongoing, multi-billion-year experiment.