Signs of Alien Life Detected on Exoplanet K2-18b, Scientists Say

Key Biological Gases Identified in Alien Atmosphere

In a major breakthrough in the search for extraterrestrial life, scientists have detected chemical signatures in the atmosphere of a distant exoplanet that are strongly associated with biological activity on Earth.

Using the James Webb Space Telescope (JWST), researchers found traces of dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) in the atmosphere of K2-18b, a planet located approximately 124 light-years from Earth in the constellation Leo.

These gases, on Earth, are exclusively produced by microbial life, primarily marine phytoplankton and algae.

Potential Evidence of Extraterrestrial Microbial Life

Researchers emphasize that this discovery does not confirm the existence of alien life. Instead, it represents the strongest potential biosignature detected outside the solar system to date.

What Are Biosignatures?

Biosignatures are chemical compounds or elements that suggest the presence of biological processes. In this case, the observed gases are known to result from living organisms on Earth.

Dr. Nikku Madhusudhan of the University of Cambridge, lead author of the study published in Astrophysical Journal Letters, described the finding as a “transformational moment” in the field of astrobiology.

K2-18b: A Hycean World in the Habitable Zone

K2-18b is a sub-Neptune planet, 8.6 times the mass of Earth, with a diameter about 2.6 times larger. It orbits within the habitable zone of a red dwarf star, where temperatures may allow liquid water to exist—a key factor in supporting life.

The planet is classified as a potential Hycean world—an exoplanet that may have a hydrogen-rich atmosphere and a liquid water ocean, ideal conditions for microbial life.

High Concentrations of DMS and DMDS Detected

The presence of DMS or DMDS was confirmed at a 99.7% confidence level, based on atmospheric concentrations above 10 parts per million—thousands of times higher than Earth’s levels. According to current scientific understanding, such concentrations cannot be explained by non-biological (abiotic) processes.

Madhusudhan added, “The only scenario that currently explains all existing data is that K2-18b is a Hycean world teeming with life. But we must remain open to other possibilities.”

Caution Urged by Scientists

Despite the excitement, researchers urge caution. The team stresses the need for:

• Repeated observations to confirm the signal’s accuracy.
• Theoretical and experimental studies to rule out abiotic causes of DMS and DMDS production.
• Independent verification by other scientific teams using new data analysis.

Other experts not involved in the study, including Dr. Christopher Glein from the Southwest Research Institute, agree that the findings are promising but require further validation.

How the Discovery Was Made

The James Webb Space Telescope identified the atmospheric gases using the transit method. As the planet passes in front of its host star, some starlight filters through the planet’s atmosphere. The telescope then captures this light and analyzes the spectral fingerprints of gases within.

Earlier data had suggested the presence of methane and carbon dioxide in K2-18b’s atmosphere. This latest research adds a significant piece to the puzzle by identifying potential biosignatures.

The Bigger Picture

To date, over 5,800 exoplanets have been discovered. Among them, Hycean worlds are emerging as some of the most promising candidates for life. Unlike Earth-like planets, these worlds may harbor life in extreme oceanic conditions under dense hydrogen-rich atmospheres.

Madhusudhan believes this discovery could shift the trajectory of the search for life.

“We have entered the era of observational astrobiology. Detecting biosignatures in habitable exoplanets is now within our technological reach,” he stated.

However, he cautioned that confirming life on another world will require significantly more research and collaboration.