Quick Read
- Astronomers detected potential biosignatures on exoplanet K2-18b, 124 light-years away.
- The James Webb Space Telescope identified dimethyl sulfide (DMS) and dimethyl disulfide in the planet’s atmosphere.
- K2-18b orbits in the habitable ‘Goldilocks’ zone, making it a prime candidate for hosting life.
- Scientists caution that more observations are needed to confirm the findings.
- The discovery could significantly advance the search for extraterrestrial life.
Astronomers Detect Potential Biosignatures on Exoplanet K2-18b
Astronomers have announced the discovery of the most promising hints of potential life on a planet beyond our solar system. Using the James Webb Space Telescope, a British-U.S. team of researchers detected signs of two chemicals in the atmosphere of exoplanet K2-18b, located 124 light-years away in the Leo constellation. These chemicals, dimethyl sulfide (DMS) and dimethyl disulfide, are considered biosignatures, as they are produced on Earth only by living organisms, primarily marine algae.
What Makes K2-18b a Prime Candidate?
K2-18b is a rare exoplanet, more than eight times the mass of Earth and 2.5 times its size. It orbits its star in the habitable ‘Goldilocks’ zone, where conditions are neither too hot nor too cold to support liquid water. This makes it a prime candidate for hosting life. The planet has long been considered a potential ‘hycean planet’—an ocean world with a hydrogen-rich atmosphere, similar to Earth but larger and hotter.
How Were the Chemicals Detected?
The James Webb Space Telescope observed K2-18b as it crossed in front of its star, allowing astronomers to analyze how molecules in its atmosphere block starlight. In 2023, the telescope detected methane and carbon dioxide in the planet’s atmosphere, marking the first time such carbon-based molecules were found on an exoplanet in a habitable zone. A year later, using its mid-infrared instrument, the telescope detected stronger signals of DMS and dimethyl disulfide.
Why Is Caution Necessary?
While the findings are exciting, scientists emphasize that more observations are needed to confirm the presence of these chemicals. The current results are below the ‘five sigma’ threshold of statistical significance required for a definitive discovery. Additionally, some experts argue that these chemicals could be produced by non-organic processes. For example, traces of DMS were found on a comet, suggesting it can form without biological activity.
What Do Experts Say?
Nikku Madhusudhan, the lead author of the study published in The Astrophysical Journal Letters, expressed optimism, stating, ‘This is the strongest evidence yet there is possibly life out there.’ He estimates that 16 to 24 more hours of observation with the James Webb Space Telescope could confirm the findings within one to two years. However, other scientists remain skeptical. Raymond Pierrehumbert, a planetary physics professor at Oxford University, argues that K2-18b is too hot to support liquid water, making it uninhabitable.
If confirmed, the discovery of biosignatures on K2-18b would be a significant milestone in the search for extraterrestrial life. It could open new avenues for exploring hycean planets and other potentially habitable worlds. Madhusudhan believes this could be the tipping point in answering the fundamental question of whether we are alone in the universe.