An artist’s impression depicts a “hycean world”—an exoplanet with an ocean of liquid water under a hydrogen-rich atmosphere—orbiting a red dwarf star. The exoplanet K2-18 b could potentially fall into this category, according to recent observations from the James Webb Space Telescope.
Key Points:
- K2-18 b has a mass 8.6 times that of Earth.
- Located 124 light-years away from Earth.
- The planet’s atmosphere contains gases similar to those produced by algae on Earth.
- While not confirming the existence of alien life, scientists say these findings are promising.
WASHINGTON — In a groundbreaking potential discovery, scientists using the James Webb Space Telescope have detected what they describe as the strongest signs of life beyond our solar system. The discovery involves the identification of chemical traces in the atmosphere of an exoplanet that are typically associated with biological activity on Earth.
The two gases—dimethyl sulfide (DMS) and dimethyl disulfide (DMDS)—found in the atmosphere of K2-18 b are produced by living organisms on Earth, particularly marine microorganisms like phytoplankton. This discovery has raised the possibility that microbial life could exist on the planet. However, researchers emphasize that they are not claiming to have discovered actual extraterrestrial life but instead have found what might be a biosignature, which suggests the presence of biological processes. More observations are needed to confirm the findings.
Astrophysicist Nikku Madhusudhan, lead author of the study published in The Astrophysical Journal Letters, expressed excitement over the discovery. “This marks a transformative moment in the search for life beyond our solar system,” said Madhusudhan. “We’ve demonstrated that it’s possible to detect biosignatures in potentially habitable planets using current technologies. We are entering the era of observational astrobiology.”
While many researchers are focused on finding life within our own solar system—on Mars, Venus, or moons like Europa and Enceladus—Madhusudhan sees this as a breakthrough. K2-18 b is a planet that is about 8.6 times as massive as Earth and has a diameter approximately 2.6 times larger than ours. It orbits a red dwarf star, which is smaller and less luminous than our Sun, situated about 124 light-years away in the constellation Leo.
A ‘Hycean World’
The planet falls into the category of “hycean worlds,” a term used for exoplanets that could have oceans of liquid water covered by a hydrogen-rich atmosphere. Scientists have hypothesized that such planets could potentially support life, particularly microbial organisms.
Previously, the Webb telescope had detected methane and carbon dioxide in K2-18 b’s atmosphere, which was the first discovery of carbon-based molecules in the atmosphere of a planet located in a star’s habitable zone. Madhusudhan stated that the combination of all Webb’s findings points to the possibility that K2-18 b could be a hycean world teeming with life. However, he stressed that alternative explanations for the data should also be considered.
“If these hycean worlds exist, we’re likely talking about microbial life, much like the organisms we find in Earth’s oceans,” Madhusudhan said. He noted that the oceans on K2-18 b might be warmer than Earth’s, but the idea of complex multicellular or intelligent life is still far from being confirmed.
The gases DMS and DMDS are known to be associated with biological processes on Earth. Webb’s observations showed their presence in K2-18 b’s atmosphere with a 99.7% confidence level, meaning the possibility of this being a statistical error is very small.
“The concentrations of these gases are thousands of times higher than they are in Earth’s atmosphere, and based on our current understanding, this could only be explained by biological activity,” Madhusudhan explained.
Caution from Experts
Although the discovery is exciting, other scientists caution against jumping to conclusions. Christopher Glein, a scientist at the Southwest Research Institute in Texas, called the data from K2-18 b “tantalizing” but urged careful analysis before drawing definitive conclusions.
“This data is an important step forward in understanding exoplanets, but we must proceed with caution and conduct further tests,” Glein stated. “I look forward to seeing additional independent analyses in the coming weeks.”
The Transit Method
K2-18 b is part of the “sub-Neptune” class of exoplanets, which have diameters larger than Earth’s but smaller than Neptune. To study the chemical composition of its atmosphere, astronomers use the “transit method,” where they observe how the planet passes in front of its star. As the planet transits, some of the star’s light passes through its atmosphere, allowing scientists to analyze the gases present.
Webb’s earlier observations hinted at the presence of DMS, but these new findings, gathered using a different instrument and light wavelength range, provide stronger evidence.
Madhusudhan described the search for signs of life on Earth-like exoplanets as the “Holy Grail” of exoplanet science. “Humanity has wondered for millennia if we are alone in the universe, and now we might be on the verge of detecting life beyond Earth. But we must proceed carefully.”
He added that further confirmation would require repeating the observations to ensure the signal is robust and free from statistical error. Additionally, more theoretical and experimental work is needed to explore whether abiotic (non-biological) processes could also explain the presence of DMS and DMDS.
As Madhusudhan said, while these findings are exciting, they should not be mistaken for proof of extraterrestrial life just yet. “At this stage, it’s still a big ‘if.’ It’s essential not to claim prematurely that we’ve detected life.”
