COSMOS MAGAZINE: In 2023, an exoplanet made international headlines because James Webb Space Telescope (JWST) observations suggested that the planet has a “biosignature” – signs of gas in its atmosphere produced by “life.”
A new study published in the Astrophysical Journal Letters pricks a hole in this hypothesis.
K2-18b is a planet orbiting a star more than 110 light-years from Earth. The planet is in the habitable “Goldilocks” zone – that is, its orbit lies within the distance where it is not too cold and not too hot, and can sustain liquid water. It was discovered in 2015 by the Kepler Space Telescope.
“The DMS signal from the Webb telescope was not very strong and only showed up in certain ways when analysing the data,” says University of California, Riverside (UCR) astronomer Shang-Min Tsai, lead author of the new paper. “We wanted to know if we could be sure of what seemed like a hint about DMS.”
“The best biosignatures on an exoplanet may differ significantly from those we find most abundant on Earth today,” says senior author and UCR astrobiologist Eddie Schwieterman. “On a planet with a hydrogen-rich atmosphere, we may be more likely to find DMS made by life instead of oxygen made by plants and bacteria as on Earth.”