There's a Striking Flaw in That Claim About Alien Life on a Nearby Planet

A team of astronomers recently announced that they've detected a possible sign of life on an exoplanet 124 light years away using the James Webb Space Telescope. Even more enticingly, the exoplanet, dubbed K2-12b, was already suspected to be an ocean world. The biosignature is a molecule called dimethyl sulfide. On Earth, it's exclusively produced by phytoplanktons and other microbes. Thus, the authors of the new study, published in The Astrophysical Journal Letters, maintain that the best explanation for the detection is that K2-12b is brimming with life. But it may not be so clearcut. While dimethyl sulfide is an […]

Apr 18, 2025 - 15:19

There's a Striking Flaw in That Claim About Alien Life on a Nearby Planet

There's significant questions about whether biosignature that the astronomers detected on the exoplanet is actually a sign of life.

A team of astronomers announced this week that they've detected a possible sign of life on an exoplanet 124 light years away using the James Webb Space Telescope. Even more enticingly, the exoplanet, dubbed K2-12b, was already suspected to be an ocean world.

The biosignature is a molecule called dimethyl sulfide. On Earth, it's exclusively produced by phytoplanktons and other microbes. Thus, the authors of the new study, published in The Astrophysical Journal Letters, maintain that the best explanation for the detection is that K2-12b is brimming with life.

But the situation may not be so clear cut. While dimethyl sulfide is an organic material on our planet, there's a body of evidence suggesting that nonbiological processes elsewhere in the cosmos could produce the compound, notes science writer Corey S. Powell in a Bluesky thread.

A study published this February reported a possible detection of dimethyl sulfide in the interstellar medium, the clouds of gas and dust found in the space between stars. Another paper published last year showed that the molecule could be produced from interactions with UV light in a lab analog of an exoplanet atmosphere. Astronomers have also found the putative biosignature on a completely barren comet.

Needless to say, all this strongly call into question if the mere presence of dimethyl sulfide's is anything approaching a definite indicator of extraterrestrial life.

The researchers behind the latest paper, for their part, seem to want to have it both ways: a splashy announcement with quotable moments about its immense significance, but sprinkled with notes of caution that cover their butts if the findings turn out to show something else.

"It is in no one's interest to claim prematurely that we have detected life," Nikku Madhusudhan, an astronomer at the University of Cambridge and lead author of the recent discovery, said at a Tuesday news conference, as quoted by the NYT.

Nonetheless, he called it a "revolutionary moment."

"It's the first time humanity has seen potential biosignatures on a habitable planet," Madhusudhan added.

Notably, NASA, which released a press release for Madhusudhan's previous work that found methane and carbon in K2-12b's atmosphere, didn't comment on this latest study.

K2-12b appears to be larger than Earth, with five times the mass, but is smaller than Neptune. It orbits in its star's "Goldilock's zone," where temperatures are just right to have liquid water on its surface. Madhusudhan's work indicates that the exoplanet's atmosphere is swamped with levels of dimethyl sulfide thousands of times higher than on Earth.

Even if dimethyl sulfide is a reliable biosignature, some astronomers are skeptical that it's been detected here.

The detection seems "tentative," Edward Schwieterman, an astrobiologist at the University of California, Riverside who wasn't involved in the research, told NPR. "It is not a sure thing."

Schwieterman suspected that the signal might go away when other teams take a look.

"I think this is one of those situations where extraordinary claims require extraordinary evidence," Laura Kreidberg, an astronomer at the Max Planck Institute for Astronomy in Germany who was not involved in the research, told NPR. "I'm not sure we're at the extraordinary evidence level yet."

More on exoplanets: James Webb Space Telescope Captures Images of Individual Planets in Distant Star System

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