Scientists in the U.K. may have uncovered the strongest evidence yet of life beyond our solar system.
The discovery, involving the distant exoplanet K2-18b, was announced Tuesday during a press conference at the University of Cambridge.
The research, led by University of Cambridge professor Nikku Madhusudhan, found that NASA’s James Webb Space Telescope detected the chemical signatures of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in K2-18b’s atmosphere.
“This is a very important molecule, because here on Earth, DMS is produced uniquely by life—microorganisms in the ocean, like algae, phytoplankton,” Madhusudhan said in a video presentation.
“Theoretical studies had predicted for the last two decades that molecules like DMS would be robust biomarkers on exoplanetary systems, including planets with hydrogen-rich atmospheres."
The discovery of K2-18b is part of space agencies and academia's continued exploration of distant planets. In July, the Perseverance rover discovered a Martian rock called “Cheyava Falls” in the Jezero Crater.
The rock contains organic molecules, offering new clues in the ongoing hunt for past or present life beyond Earth.
K2-18b orbits a red dwarf star about 124 light-years away, around 729 trillion miles from Earth. The planet has roughly 8.6 times Earth's mass and a radius about 2.6 times larger.
It lies within its star’s habitable zone—an area where an Earth-like planet could potentially support life.
Reading the signs
Scientists used transit spectroscopy to study K2-18b’s atmosphere. As the planet passes in front of its star, some starlight filters through its atmosphere. By analyzing which wavelengths are absorbed, scientists can determine the atmosphere’s composition.
“Some of the starlight passes through the planet's atmosphere before reaching the telescope, and the molecules in that atmosphere absorb certain wavelengths,” Madhusudhan explained. “By looking at a differential measurement when the planet is in front of the star or when it isn't, you can extract how much absorption is happening in the planet's atmosphere.”
In 2023, researchers using the James Webb Space Telescope reported a tentative detection of dimethyl sulfide in the atmosphere of K2-18b while observing in the one to five micron wavelength range—part of the infrared spectrum used to detect heat and molecular signatures.
While researchers are confident in their “three sigma” detection of DMS on K2-18b—a statistical confidence level indicating a strong result—Madhusudhan emphasized the need for additional observations to confirm the finding.
“This is one of the most profound moments for me personally and as an astronomer, because for the first time in our species' history, we may be seeing signs of life elsewhere,” he said.
Madhusudhan acknowledged, however, that the signal could result from a previously unknown chemical process unrelated to life. Still, Madhusudhan remained optimistic about the finding and its implications for extraterrestrial life.
“Even that is a monumental breakthrough, because we are seeing new chemical processes on a planet that could be habitable—something we’ve shown is possible in theoretical studies,” he said.
“This is, in my view, a transformational moment—not just for planetary science, not just for astronomy, but for finding our place in the universe as a species.”
Edited by Sebastian Sinclair