Astronomers thought they found signs of life on distant planet. New studies are skeptical

USA Today

30-05-2025

Astronomers thought they found signs of life on distant planet. New studies are skeptical A series of studies have cast doubt on the sensational claim that "the strongest evidence yet" was found that life exists anywhere else besides Earth.
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Astronomers find possible signs of alien life on distant planet K2-18b
Astronomers plan to conduct more research after finding possible signs of alien life on a distant exoplanet known as K2-18b.
The findings came from a team of researchers at the University of Cambridge who studied data from NASA's James Webb Space Telescope to find molecules in the atmosphere of a planet known as K2-18b.
On Earth, the gases are only produced by life, primarily microbial life such as marine algae like phytoplankton, according to the researchers.
Since then, other independent astronomers who took their own look at the data and came to their own highly skeptical conclusions.
Back in April, the world became captivated by the news that maybe, just maybe, we weren't alone in the universe after all.
If extraterrestrials were to exist on a distant exoplanet as a team of astronomers theorized, it wouldn't exactly be intelligent life, but – hey – it was something. The explosive findings came from a team of researchers at the University of Cambridge who studied data from NASA's James Webb Space Telescope to find molecules in the atmosphere of a planet known as K2-18b that could have been created by organisms akin to marine algae.
But then along came other independent astronomers who took their own look at the data and came to their own highly skeptical conclusions. A series of studies since the April 17 announcement have cast doubt on the sensational claim that what the initial researchers had found was "the strongest evidence yet" that life exists anywhere else besides Earth.
"The data we have so far is much too noisy for the proof that would be needed to make that claim,' Rafael Luque, an astronomer at the University of Chicago, who led the most recent study, said in a statement. 'There's just not enough certainty to say one way or the other.'
Here's everything to know about K2-18b, and just what potential it has to harbor alien life.
What is exoplanet K2-18b?
K2-18b, which orbits a red dwarf star more than 120 light-years from Earth, has for years intrigued astronomers who believe it could be among the best places to search for signs of extraterrestrial life.
The cosmic body is an exoplanet, meaning it orbits a star outside of Earth's own solar system.
First discovered in 2015 during NASA's planet-hunting K2 mission, K2-18b likely orbits its star in what astronomers refer to as the "habitable zone" – where conditions could allow for water. In a nod to the classic fairy tale, astronomers even refer to these regions as "Goldilocks" zones because conditions have to be just right – neither too hot nor too cold – for water to remain in liquid form and pool on planetary surfaces.
Interestingly, K2-18b, which is 8.6 times bigger than Earth, isn't rocky like our planet. Rather, observations have allowed scientists to conclude that the exoplanet could be a Hycean world covered by ocean water underneath a hydrogen-rich atmosphere.
Could alien life thrive on K2-18b? What to know about the distant exoplanet
Have they found life on K2-18b?
The latest findings on K2-18b came from a team of researchers led by Nikku Madhusudhan, an astrophysicist at the University of Cambridge in England.
Because the planet is too far and too faint to observe directly with ground telescopes, astronomers had to get creative.
In this case, the team studied data from the Webb Telescope gathered from observing K2-18b as the planet crossed in front of its star, causing starlight to filter through the planet's atmosphere. As the light passed through the planet's atmosphere, different amounts of light were blocked at different wavelengths, depending on what molecules are present.
That's what led Madhusudhan and his team to detect hints of sulfur-based gases dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the atmosphere – both molecules from the same chemical family.
On Earth, the gases are only produced by life, primarily microbial life such as marine algae like phytoplankton, according to the researchers.
Scientists cast doubt on signs of alien life on K2-18b
Since then, at least three different studies have largely dismissed the notion that any compelling evidence has been found to yet suggest life exists on K2-18b.
In the most recent study led by Luque, researchers reviewed data from multiple observations of the planet.
After combining observations of K2-18b in both the near-infrared light and longer wavelengths of mid-infrared light, the team concluded that it did not detect dimethyl sulfide. What's more, they found that other molecules, not just those possibly indicating signs of life, could explain the questionable discovery.
In an earlier study published to arXiv, Jake Taylor, an astrophysicist at the University of Oxford, took a look at the Webb telescope data using a common data model for exoplanet studies and came to much the same conclusion: Taylor found no evidence of the atmospheric clues that were so integral in the Cambridge study's findings.
Madhusudhan, who has issued rebuttals to some of the findings dismissing his potential discovery, has readily acknowledged that his team's observations are in need of further review. In announcing the findings, Madhusudhan conceded the molecules observed could have occurred by chance or could be the result of previously unknown chemical processes at work on K2-18b.
Regardless, it appears astronomers all agree that we may not be as close as we thought to determining whether anything does indeed live on K2-18b.
'Answering whether there is life outside the solar system is the most important question of our field. It is why we are all studying these planets,' Luque said in a statement. 'We are making enormous progress in this field, and we don't want that to be overshadowed by premature declarations.'
Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at [e-mail]