A team of astronomers from the University of Cambridge published new evidence in April of potential signs of life on an ocean planet 124 light-years from Earth. The planet called K218B is what some scientists are calling the best evidence of extraterrestrial life humanity has discovered. 

The scientists reported the presence of a molecule called dimethyl sulfide on K218B; on Earth, this molecule is only created by life. If this discovery is true, it represents the first time a biosignature, or indication of biological presence, has been found on a potentially habitable planet. 

Astronomy Club President Kishor Rajmohan said biosignatures can be a strong indicator of life. 

“If you haven’t actually observed life, but you’ve observed something that indicates life, what are the chances that that thing happened without life being there?” Rajmohan said. “Biosignatures are probably close to the top of that probability list.” 

He also said astronomers can see the atmospheric composition of distant planets by detecting light that has passed through the exoplanet’s atmosphere before reaching Earth. 

“When it passes through the atmosphere, different wavelengths of light are absorbed by whatever is in the atmosphere,” Rajmohan said. “Based on what wavelengths of light are absorbed, you can see what’s in the atmosphere.”

The team of astronomers first reported traces of dimethyl sulfide on K2-18B in 2023. In 2024, they got another chance to view the planet using the James Webb Telescope and found an even stronger signal of dimethyl sulfide and another compound called dimethyl disulfide, suggesting the planet’s oceans are full of algae. 

Despite the promising data, discussion within the scientific community has raised questions about the legitimacy and significance of these findings. Researcher Jake Taylor from the University of Oxford conducted another study and found too much interfering noise for a conclusive result. 

Additionally, Laura Kreidberg from the Max Planck Institute for Astronomy told NPR scientists make certain assumptions throughout the research process, which can impact the results of the research. If the signal exists, it should show up regardless of researchers’ assumptions. 

Additionally, Christopher Glein from the Southwest Research Institute posted a paper on April 13 that suggested K2-18B might not be a habitable planet. It may instead have a scorching hydrogen atmosphere and magma oceans. 

Astrophysics teacher Joshua Bloom said while discoveries like these are exciting, it may be a long time before any conclusions can be drawn. 

“They are only one piece of a larger body of evidence required to prove that life is not unique to Earth,” Bloom said “We are a long way from being able to see direct evidence of life on other planets. But we do now have the tools to discover indirect evidence of life.” 

Bloom also said further evidence is needed to corroborate these findings. 

“This most recent discovery is exciting since it is something we would expect to see if something biological were present on this distant planet,” Bloom said. “But there might be other explanations. What we need is more than one piece of evidence that, when taken together, makes it extremely unlikely there is any other explanation that could explain all those observations (other) than the presence of life.”