ETH Study Dampens Hopes of Life in Space

(CONNECT) A study led by the Swiss Federal Institute of Technology in Zurich (ETH) concludes that life-friendly water resources on so-called sub-Neptunes are unrealistic. It was previously assumed that some of these planets, which are smaller than Neptune but larger than Earth, were able to accumulate a particularly large amount of water during their formation and today harbor global, deep oceans under a hydrogen-rich atmosphere. "Our calculations show that this scenario is not possible," Caroline Dorn, Professor of Exoplanets at ETH, is quoted as saying in a report from her university.

In doing so, her research group, together with scientists from the Max Planck Institute for Astronomy in Heidelberg and the University of California in Los Angeles, dashed a hope that had made headlines in spring 2025: researchers from the University of Cambridge had reported that the planet K2-18b could be a water world full of life.

The present study took into account what previous investigations had ignored: the chemical coupling between the atmosphere and the interior of the respective planet. The researchers calculated the chemical equilibrium state of 26 different components for a total of 248 model planets. The computer simulations showed that the chemical processes destroy most of the H2O water molecules. Hydrogen and oxygen attach themselves to metallic compounds, and these largely disappear into the core of the planet.

This makes the search for extraterrestrial life more difficult than hoped. The researchers conclude that life-friendly conditions with sufficient liquid water on the surface probably only exist on smaller planets such as Earth. And these will probably only be observable outside our solar system with observatories that are even better than the James Webb Space Telescope. ce/mm