Artist’s impression of the planet K2-18b and its host star
ESA/Hubble, M. Kornmesser
Astronomers have recently reported what they believe is the strongest evidence yet for potential life on another planet. However, caution is advised until the findings are confirmed by additional research groups and alternative explanations are thoroughly explored.
According to Nikku Madhusudhan from the University of Cambridge, “These are the first hints we are seeing of an alien world that is possibly inhabited.”
The exoplanet K2-18b was first discovered in 2015 and was identified as a promising candidate for hosting life. With a mass about eight times that of Earth and located in the habitable zone of its star 124 light years away, K2-18b offers conditions suitable for liquid water. Subsequent observations in 2019 revealed the presence of water vapor, leading to speculations about oceans beneath a hydrogen-rich atmosphere, although not all experts were in agreement.
In 2023, Madhusudhan and his team utilized the James Webb Space Telescope to examine K2-18b’s atmosphere in near-infrared light, detecting water vapor, carbon dioxide, and methane. They also observed a faint signal of dimethyl sulphide (DMS), a molecule typically associated with biological activity on Earth. While the DMS signal was initially weak, a recent study using a different instrument on the JWST found a stronger signal for both DMS and dimethyl disulphide (DMDS), compounds indicative of life.
Madhusudhan explained, “What we are finding is an independent line of evidence in a different wavelength range with a different instrument of possible biological activity on the planet.”
The team’s claim of detecting DMS and DMDS is at a three-sigma level of statistical significance, suggesting a 3-in-1000 chance of a random occurrence. However, the standard threshold for confirming a discovery in physics is five sigma, equivalent to a 1-in-3.5 million chance of data being coincidental.
Nicholas Wogan from NASA Ames Research Center acknowledged the compelling nature of the evidence but emphasized the need for verification by independent researchers. He highlighted the complexity involved in analyzing JWST data and the time required for confirmation.
On the other hand, Ryan MacDonald from the University of Michigan expressed skepticism, citing previous instances where promising signals on K2-18b were eventually disproven upon closer examination. He stressed the importance of rigorous scrutiny before claiming the presence of extraterrestrial life.
Madhusudhan’s team estimates that additional observations totaling 16 to 24 hours with the JWST could elevate the evidence to the five-sigma threshold. However, challenges in accurately measuring the planet’s atmosphere, likened to the thickness of an apple skin, may complicate this process.
Regardless of the origin of the detected compounds, the implications of the findings are significant. Madhusudhan emphasized the revolutionary nature of the discovery and the technological advancements enabling humanity to explore potential signs of life on distant planets.
Mysteries of the universe: Cheshire, England
Spend a weekend with some of the brightest minds in science, as you explore the mysteries of the universe in an exciting programme that includes an excursion to see the iconic Lovell Telescope.
