Are we alone in this universe? Do aliens exist? Is there life outside planet Earth? These questions intrigue humans, forcing them to explore deep space. Jupiter’s Moon Europa, plumes of methane on Mars and clouds of phosphine gas on Venus were some of the top contenders in this massive search, but now a giant planet has yielded the strongest evidence yet that extraterrestrial life may be thriving outside our planet.
K2-18b is a fascinating exoplanet located about 124 light-years away from Earth in the constellation Leo. It is not in our solar system, but after a repeated analysis of its atmosphere, scientists are sure that it has chemical fingerprints of compounds that, on Earth, are only known to be produced by life.
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Scientists have detected methane and carbon dioxide each making up about 1% of the atmosphere. Initially, the presence of water vapour was reported, but subsequent studies suggest concentrations of less than 0.1%.
In addition to these, chemicals, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) were also found, which is a sign of biological activity. It doesn’t mean there are aliens, but it surely indicates there’s life on that planet.
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“It is in no one’s interest to claim prematurely that we have detected life,” said Nikku Madhusudhan, an astronomer at the University of Cambridge and an author of the new study, at a news conference on Tuesday.
He further added that the best explanation for his group’s observations is that K2-18b is covered with a warm ocean, brimming with life. “This is a revolutionary moment. It’s the first time humanity has seen potential biosignatures on a habitable planet,” Dr Madhusudhan said.
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Scientists have ‘strongest evidence’
“This is the strongest evidence to date for a biological activity beyond the solar system,” Dr Madhusudhan said, further adding, “We are very cautious. We have to question ourselves both on whether the signal is real and what it means.”
He added: “Decades from now, we may look back at this point in time and recognise it was when the living universe came within reach. This could be the tipping point, where suddenly the fundamental question of whether we’re alone in the universe is one we’re capable of answering.”
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In 2023, Webb found the presence of carbon-bearing molecules, including methane and carbon dioxide. Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet.
The latest study was published on Wednesday in the Astrophysical Journal, and this new theory has excited other researchers. As quoted by The New York Times, Stephen Schmidt, a planetary scientist at Johns Hopkins University, said, “It’s not nothing. It’s a hint. But we cannot conclude it’s habitable yet.”
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As quoted by the NYT, Christopher Glein, a planetary scientist at the Southwest Research Institute in San Antonio, Texas, said, “Unless we see E.T. waving at us, it’s not going to be a smoking gun.”
Notably, the presence of methane, carbon dioxide and possibly DMS could indicate biological processes, but geological or chemical origins are also possible. Hence, further studies are needed to confirm the presence of life or biosignatures on K2-18b.