A team of researchers led by Indian-origin astrophysicist Dr. Nikku Madhusudhan at the University of Cambridge has announced what may be the strongest evidence yet for extra-terrestrial life, based on observations of the exoplanet K2-18b, located over 120 light-years from Earth.

Using NASA's James Webb Space Telescope (JWST), the team detected compelling chemical signatures in the planet's atmosphere, most notably the presence of dimethyl sulphide (DMS) and dimethyl disulphide (DMDS)—molecules that, on Earth, are produced almost exclusively by living organisms such as marine algae and phytoplankton.

K2-18b is a sub-Neptune exoplanet, about 2.6 times the size and 8.6 times the mass of Earth, orbiting within the habitable zone of its parent red dwarf star, K2-18, in the Leo constellation. This region is considered suitable for the existence of liquid water, a key ingredient for life as we know it.

Dr. Madhusudhan's team has previously proposed that such sub-Neptunes could be "Hycean" worlds—planets with hydrogen-rich atmospheres and vast, warm oceans beneath, potentially offering a unique environment for life to thrive.

The JWST observations revealed not only DMS and DMDS but also methane and carbon dioxide, further supporting the hypothesis of a chemically active, possibly life-supporting atmosphere. The detected concentration of DMS in K2-18b's atmosphere is estimated to be thousands of times higher than on Earth, which, if biologically sourced, would imply a planet teeming with microbial life. 

However, the detection currently stands at a "three sigma" confidence level (99.7% certainty), which, while statistically significant, falls short of the "five sigma" (99.99994%) standard required for a definitive scientific discovery.

Despite the excitement, Dr. Madhusudhan and other scientists caution against premature conclusions. While the presence of DMS is a strong biosignature on Earth, alternative, non-biological processes could potentially explain its abundance on K2-18b, especially given the planet's exotic conditions. Some researchers suggest that K2-18b might not be a Hycean world but could instead be a rocky planet with a magma ocean and a thick hydrogen atmosphere, which would not support life as we know it.

The findings, published in the Astrophysical Journal Letters, represent a transformative step in the search for life beyond our solar system, marking the first time potential biosignatures have been detected on a habitable-zone exoplanet. The scientific community remains cautious but optimistic, with further JWST observations and laboratory experiments planned to confirm the presence of DMS and refine models of K2-18b's atmosphere. If confirmed, this discovery could revolutionize our understanding of life's prevalence in the galaxy and open new avenues in observational astrobiology.

As Dr. Madhusudhan remarked, "This is a revolutionary moment... It's the first time humanity has seen potential biosignatures on a habitable planet". However, as other experts note, much work remains before the claim of extra-terrestrial life can be substantiated, and the search will continue with future space telescopes and missions.

ANI