Scientists Just Found the ‘Strongest Evidence’ of Alien Life Yet

It’s 124 light-years away, wrapped in a steamy hydrogen-rich atmosphere, and just might be crawling with alien microbes.

K2-18b, a distant exoplanet orbiting a star in the Leo constellation, has officially become the most promising candidate yet in the search for life beyond Earth. Using the James Webb Space Telescope, scientists say they’ve picked up the “strongest evidence yet” of possible biosignatures in its atmosphere—specifically, dimethyl sulfide (DMS), a compound on Earth that’s only produced by living organisms like phytoplankton.

“This is the strongest evidence yet there is possibly life out there,” said lead researcher Nikku Madhusudhan of Cambridge University. “I can realistically say that we can confirm this signal within one to two years.”

Are Aliens Out There? Maybe.

The potential is massive, but so is the caution. Researchers aren’t calling this a discovery—yet. The presence of DMS and its cousin dimethyl disulfide could hint at microbial life, but they’re still below the gold-standard “five sigma” confidence level. Right now, the odds of this being a fluke are about the same as flipping a coin ten times and getting heads every time, according to Cambridge statistician Stephen Burgess.

But if Webb captures just 16–24 more hours of data, Madhusudhan says we could reach five sigma—meaning the signal almost certainly isn’t a coincidence. “This could be the tipping point,” he said, “where suddenly the fundamental question of whether we’re alone in the universe is one we’re capable of answering.”

Still, some scientists aren’t sold. Previous studies have mistaken other gases for water vapor on K2-18b, and similar compounds have been spotted on comets, which suggests non-biological origins are possible. “It would be hellishly hot,” said Oxford professor Raymond Pierrehumbert, who believes the planet is more likely to host oceans of lava than microbial life.

K2-18b is what scientists call a “hycean planet”—a world larger than Earth, likely covered in oceans, and with an atmosphere rich in hydrogen. These planets aren’t expected to host anything intelligent, but they could be full of primitive life similar to what existed in Earth’s early oceans.

And if those DMS signals hold up? We may finally have an answer to the biggest question we’ve ever asked. Or, at the very least, we’re closer than we’ve ever been.