Astronomers have detected the most promising signs so far of possible life beyond our solar system.
Using the powerful James Webb Space Telescope (JWST), an international team led by the University of Cambridge has found chemical hints in the atmosphere of a distant planet that may be linked to biological activity.
The planet, K2-18b, orbits a star about 124 light-years away in the constellation Leo and lies in the “habitable zone,” where conditions might allow for liquid water.
Previous research had already detected methane and carbon dioxide in the planet’s atmosphere—carbon-based molecules that are linked to life as we know it.
But now, astronomers have identified a new clue: the presence of dimethyl sulfide (DMS) or dimethyl disulfide (DMDS), two molecules on Earth that are only produced by living organisms, mostly by ocean-dwelling microbes like phytoplankton.
This finding doesn’t mean life has been discovered just yet.
The signal from the planet’s atmosphere has reached what scientists call “three-sigma” certainty, meaning there’s about a 0.3% chance the detection happened by accident. For scientists to confidently claim a discovery, they need “five-sigma” certainty—less than a 0.00006% chance of it being a fluke.
The researchers believe that 16 to 24 more hours of observation with JWST could help reach that crucial level of certainty.
K2-18b is a so-called “Hycean” planet, which means it may be covered by an ocean and surrounded by a hydrogen-rich atmosphere.
In this kind of environment, sulfur-based gases like DMS and DMDS could be present in high levels. The research team found that the concentration of these molecules on K2-18b appears to be thousands of times higher than on Earth.
To detect these molecules, scientists studied the starlight that filters through the planet’s atmosphere as it passes in front of its star.
By examining which wavelengths of light are absorbed, they can figure out which gases are present.
The new detection was made using JWST’s Mid-Infrared Instrument (MIRI), which observes a different part of the light spectrum than previous instruments used to study the planet. This independent observation strengthens the evidence that the signal is real.
Professor Nikku Madhusudhan, who led the research, said the data match earlier predictions about what kinds of gases might be found on Hycean planets. He emphasized, however, that more studies are needed. It’s possible that some unknown non-living chemical process is creating the DMS and DMDS.
While the researchers are excited, they are also cautious. Co-author Subhajit Sarkar said that the presence of these possible biosignatures raises profound questions about what might be creating them. The team now plans to run further tests and simulations to explore whether life is the only explanation.
For now, scientists are not declaring the discovery of alien life—but they agree that something remarkable may be happening on K2-18b. With tools like JWST and future space telescopes, humanity is closer than ever to answering one of its oldest questions: are we alone in the universe?
Source: University of Cambridge.
