UK researchers have claimed to have found a possible sign of life on a faraway planet. Scientists from the University of Cambridge have announced the detection of a gas that on Earth is only made by living organisms.

The discovery, which was made using NASA’s James Webb Space Telescope, could be the strongest hint yet of life beyond Earth.

The team studied K2-18 b, a planet about 124 light-years away in the Leo constellation. It is known as a “hycean” planet, meaning it may have a hydrogen-rich atmosphere and liquid water oceans. Such conditions make it a promising candidate for life.

The telescope detected dimethyl sulfide and dimethyl disulfide in the planet’s air. On Earth, both gases are made only by living organisms, mainly marine microbes such as phytoplankton. Levels of these compounds on the planet K2-18 b were found to be thousands of times higher than those on Earth.

Dr. Nikku Madhusudhan, a Cambridge University astrophysicist and lead author of the study published in The Astrophysical Journal Letters on Thursday, said the implications could be profound.

The findings “provide new independent evidence for the possibility of a biosphere on K2-18 b,” the study claimed. “What we are finding at this point are hints of possible biological activity outside the solar system,” he told a press conference. “Frankly, I think this is the closest we have come to seeing a feature that we can attribute to life,” he added.

Madhusudhan explained that detecting chemical fingerprints of gases that on Earth are created only through biological processes could point to a potentially inhabited alien world. “This is a revolutionary moment,” he added.

However, the team warned that the detected gases could also be the result of unknown natural processes. Additional telescope observations are needed to determine if living organisms truly are the source.