The subsurface ocean on Saturn’s moon Enceladus appears stable over geological timescales, enhancing its potential as a habitat for extraterrestrial life. New analysis of Cassini spacecraft data reveals heat emissions from the moon’s north pole that balance the ocean’s energy input. This stability provides the long-term conditions necessary for life to evolve.
Enceladus, a moon of Saturn, has long been considered a prime candidate for hosting extraterrestrial life due to its hidden liquid water ocean beneath an icy crust. The ocean contains liquid water, organic molecules, and heat, but until now, its long-term stability was uncertain.
Researchers, led by Carly Howett at the University of Oxford, analyzed data from NASA’s Cassini-Huygens spacecraft, which orbited Saturn from 2004 to 2017. The moon’s interior is warmed by tidal forces from Saturn’s gravity, causing it to flex and generate heat. Previously, significant heat leakage was only observed from the south polar regions, leaving a mismatch between heat input and output.
The team discovered that the north pole is about 7 degrees warmer than earlier estimates. When combined with south pole emissions, this heat nearly exactly matches the total energy input to the ocean. The ice shell is thicker at the equator, limiting heat escape there and channeling it to the poles.
“For the first time we can say with certainty that Enceladus is in a stable state, and that has big implications for habitability,” Howett said. “We knew that it had liquid water, all sorts of organic molecules, heat, but the stability was really the final piece of the puzzle.”
This balance suggests the ocean will neither freeze soon nor has it recently, providing the extended time required for life to develop. “It’s really hard to put a number on it, but we don’t think it’s going to freeze out any time soon, or that it’s been frozen out any time recently,” Howett added. “We know life needs time to evolve, and now we can say that it does have that stability.”
NASA and the European Space Agency have upcoming missions planned to search for signs of life on Enceladus in the coming decades. The findings were published in Science Advances (DOI: 10.1126/sciadv.adx4338).