By Stephanie Dwilson | 2025-05-09

A University of Cambridge team last month published compelling new evidence pointing to possible life on a planet beyond Earth.

The team made the discovery while using the James Webb Space Telescope (JWST) to study K2-18 b -- an exoplanet 124 light years from Earth.

K2-18 b is 8.6 times as massive and 2.6 times as large as Earth.

They made their case based on the detection of of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) -- gases linked to biological processes on Earth.

The team's paper was published April 17 in The Astrophysical Journal Letters.

Their findings also make a strong case for NASA's proposed Habitable Worlds Observatory telescope.

Life on another planet?

The study is a follow-up to a paper the team published in 2023, when it detected methane and carbon dioxide in the planet's atmosphere.

In the previous research, the team used JWST's NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) instruments, which together cover the near-infrared (0.8- to 5-micron) range of wavelengths.

The new evidence was found using JWST's MIRI (Mid-Infrared Instrument) in the mid-infrared (6- to 12-micron) range.

"Our findings provide new independent evidence for the possibility of a biosphere on K2-18 b," the paper said.

"Our present MIRI abundance estimates of DMS and/or DMDS … could, therefore, imply stronger biological activity on the planet in comparison to Earth," it added.

The concentrations of DMS and DMDS in K2-18 b's atmosphere, however, are much stronger than on Earth, where they are generally below one part per billion by volume, the university's report noted.

"On K2-18 b, they are estimated to be thousands of times stronger -- over 10 parts per million," it said.

"Earlier theoretical work had predicted that high levels of sulfur-based gases like DMS and DMDS are possible on Hycean worlds," Nikku Madhusudhan, who led the team, said in a report published by the university.

"Now we've observed it, in line with what was predicted. Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have."

More studies needed

Not all scientists agree with the team's findings.

Jake Taylor of the University of Oxford, a Glasstone Fellow in Astrophysics, did a quick, independent analysis of the findings and on April 22 posted a preprint paper that he submitted to AAS Journals.

Taylor used a basic statistical test to identify telltale signs of gas molecules in the atmosphere of K2-18 b without assuming which gases might be present.

Rather than observing distinct bumps that typically indicate the presence of detectable gas molecules, Taylor saw the data as consistent with a "flat line."

"I conclude no strong statistical evidence for spectral features," he said in his paper, which still awaits peer review.

The University of Cambridge paper acknowledged more research is needed before claiming that life has been found on another world.

"Robustly establishing both the veracity of the present findings and their possible association with life on K2-18 b needs a dedicated community effort in multiple directions -- observational, theoretical and experimental," the paper said.

Compelling research

The team emphasized again at the end of the paper that life on K2-18 b is not a foregone conclusion but said its findings are compelling enough to warrant a deeper look.

"Our work is the starting point for all the investigations that are now needed to confirm and understand the implications of these exciting findings," said co-author Savvas Constantinou, also from Cambridge's Institute of Astronomy.

"It's important that we're deeply skeptical of our own results, because it's only by testing and testing again that we will be able to reach the point where we're confident in them," Madhusudhan said. "That's how science has to work."

Eddie Schwieterman, an astrobiologist at the University of California, Riverside, who was not involved with the new research, expressed similar pragmatism.

"This is evidence of the scientific process at work," he told Space.com. "That's exactly what we want -- multiple, independent groups or individuals to analyze and interpret the same data. This is one, and hopefully more will follow."

Still, the research is exciting.

"This is the strongest evidence to date for a biological activity beyond the solar system," Madhusudhan told journalists when speaking about the paper.

Further search for life

After the team made its announcement, NASA's Webb Mission Team published an article sharing more details about how JWST works, along with its limitations in the search for life.

"If observations are made which suggest a potential biosignature gas, one of the most important implications is the need for follow-up studies," the article said. "Models can be developed for both biological and nonbiological explanations. From these, predictions are made, which can then be tested with further observations."

While JWST is not designed to search for life, it can make observations pointing to promising planets that a future Habitable Worlds Observatory could study in more detail, NASA noted.

"These early observations are laying the scientific and technical foundation for future missions, such as NASA's planned Habitable Worlds Observatory, which will specifically target Earth-like planets around Sun-like stars when it launches," the NASA Webb Mission Team wrote.

The Habitable Worlds Observatory is a proposed next-generation telescope that would be the first designed specifically to search for life on other planets and stars. If built, its mission will not start until after the launch of the Nancy Grace Roman Space Telescope, currently scheduled for May 2027.

JWST is a collaboration among NASA, the European Space Agency and the Canadian Space Agency.