Space radiation can produce some organic molecules detected on icy moons
October 26, 2025 2025-10-26 15:25Space radiation can produce some organic molecules detected on icy moons
Space radiation can produce some organic molecules detected on icy moons
New laboratory research suggests that some organic molecules previously detected in plumes erupting from Saturn’s moon Enceladus may be products of natural radiation, rather than originating from the moon’s subsurface ocean. This discovery complicates the assessment of the astrobiological relevance of these compounds.
Enceladus hides a global ocean buried beneath its frozen crust. Material from this liquid reservoir is ejected into space from cracks in the ice near the south pole, forming plumes of dust-sized ice particles that extend for hundreds of kilometers. While most of this material falls back onto the surface, some remains in orbit, becoming part of Saturn’s E ring, the planet’s outermost and widest ring.
Between 2005 and 2015, NASA’s Cassini spacecraft flew repeatedly through these plumes and detected a variety of organic molecules. The detection was viewed as evidence of a chemically rich and potentially habitable environment under the ice, where molecules essential to life could be available. However, the new study offers an explanation in which radiation, not biology, is behind the presence of at least some of these organic molecules.
To test the role of space radiation, a team of researchers led by planetary scientist Grace Richards, a postdoc at the National Institute for Astrophysics in Rome, simulated conditions near Enceladus’s surface by creating a mixture of water, carbon dioxide, methane, and ammonia, the main expected components of surface ice on Enceladus. They cooled the concoction to −200°C inside a vacuum chamber and then bombarded it with water ions, which are an important component of the radiation environment that surrounds the moon.
The radiation induced a series of chemical reactions that produced a cocktail of molecules, including carbon monoxide, cyanate, ammonium, and various alcohols, as well as molecular precursors to amino acids such as formamide, acetylene, and acetaldehyde. The presence of these simple molecules indicates that radiation could induce similar reactions on Enceladus.
Richards presented these findings at the Europlanet Science Congress–Division for Planetary Sciences Joint Meeting (EPSC-DPS 2025) in Helsinki, Finland. She and her coauthors also published a detailed report in Planetary and Space Science.
