A team of researchers published a study on April 17 that could be the strongest indication of extraterrestrial life — on a massive planet known as K2-18b. The planet is not in Earth’s solar system and orbits a star 124 light-years away.
The report, published in the Astrophysical Journal Letters, found that there could be an ocean world on K2-18b capable of hosting “microbial life,” which is the foundation of the Earth’s biosphere and is essential for all life on Earth.
The research team, made up of British and U.S. astronomers, detected two chemicals in the atmosphere using the James Webb Space Telescope. The chemicals fall under the category of “biosignatures” and could indicate extraterrestrial life: dimethyl sulfide (DMS) and dimethyl disulfide (DMDS).
“This is a revolutionary moment,” Nikku Madhusudhan, an astronomer at the University of Cambridge and one of the authors of the study, said at a news conference on Tuesday. “It’s the first time humanity has seen potential biosignatures on a habitable planet.”
What is K2-18b?
NASA categorizes K2-18b as an “exoplanet,” or a planet outside of the solar system that orbits a star that isn’t the sun. K2-18b is roughly 8.6 times larger than Earth and roughly 700 trillion miles away in the constellation Leo. It orbits its star every 33 days, which means it is closer to its star than Earth is to the sun.
In September 2023, the NASA Webb Telescope Team reported theories that K2-18b could be a hycean exoplanet, which means there could be liquid oceans and other molecular characteristics that would make the exoplanet potentially habitable.
“Hycean planets open a whole new avenue in our search for life elsewhere,” Madhusudhan explained in another report from 2021.
The two chemicals that were recently detected near K2-18b — DMS and DMDS — are produced on Earth by marine phytoplankton and bacteria.
Researchers have been studying K2-18b since 2021, but it is not the first exoplanet to be studied. Scientists have found around 5,800 exoplanets since the 1990s.
The research doesn’t say there are aliens living on K2-18b
Madhusudhan described Wednesday’s study as “the strongest evidence … there is possible life out there,” but the researchers behind this study aren’t saying there are aliens on K2-18b.
The findings instead determined that K2-18b is experiencing a biological process that Earth underwent billions of years ago.
Researchers need a five-sigma result to be as confident as possible that their findings are true. The latest research only provides a three-sigma result.
“I can realistically say that we can confirm this signal within one to two years,” Madhusudhan told the BBC.
However, even if the research team hits that five-sigma result, it’s not conclusive proof that there is life on KB-18b. They still need to figure out where the DMS and DMDS on K2-18b are coming from.
‘This could be the tipping point’
Astronomers have been debating whether life could exist on K2-18b since 2023, Space.com reported in March. This new research is a step toward answering whether life could exist beyond Earth.
“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,” Madhusudhan said.
