An international team of scientists has modeled how complex organic molecules, essential for biology, could have been incorporated into Jupiter's largest moons during their formation. The research suggests these building blocks of life were delivered from the early solar system's gas and dust disk without significant chemical alteration. The findings appear in two recent scientific papers.
Scientists from the Southwest Research Institute, Aix-Marseille University in France, and the Institute for Advanced Studies in Ireland have published studies showing how complex organic molecules (COMs) likely became part of Jupiter's four largest moons—Europa, Ganymede, Callisto, and Io—as they formed billions of years ago.
COMs, which contain carbon along with elements like oxygen and nitrogen vital for living systems, can form when icy dust grains with methanol, carbon dioxide, or ammonia are exposed to ultraviolet light or mild heating. Such conditions prevail in protoplanetary disks around young stars. The researchers combined models of disk evolution with simulations of icy particle movement to assess radiation and temperature exposures in the protosolar nebula—the cloud that birthed the Sun and planets—and in Jupiter's circumplanetary disk, where its moons assembled.
"By combining disk evolution with particle transport models, we could precisely quantify the radiation and thermal conditions the icy grains experienced," said Dr. Olivier Mousis of SwRI's Solar System Science and Exploration Division, lead author of one study. "Then we directly compared our simulations with other laboratory experiments that produce COMs under realistic astrophysical conditions. The results showed that COM formation is possible in both the protosolar nebula environment and Jupiter's circumplanetary disk."
The models indicate that a significant portion of icy grains carried newly formed COMs into Jupiter's moon-forming region. In some scenarios, nearly half of the particles transported these organics from the broader solar nebula to the circumplanetary disk, incorporating them into the moons with minimal change. Additionally, parts of Jupiter's disk reached temperatures sufficient for local COM production.
Europa, Ganymede, and Callisto are believed to host subsurface oceans beneath icy surfaces, powered by internal energy. "Our findings suggest that Jupiter's moons did not form as chemically pristine worlds," Mousis noted. "Instead, they may have accreted a significant inventory of COMs at birth, providing a chemical foundation that could later interact with the liquid water in their interiors."
These insights come ahead of NASA's Europa Clipper and the European Space Agency's Juice missions, which are en route to study the moons' composition and habitability. "Establishing credible pathways for COMs formation and delivery provides scientists with a critical framework for interpreting upcoming measurements," Mousis added.
The results were detailed in The Planetary Science Journal (DOI: 10.3847/PSJ/ae3559) and Monthly Notices of the Royal Astronomical Society (DOI: 10.1093/mnras/staf2074), both from 2026.
