New research from NASA's Cassini mission indicates that Saturn's moon Enceladus releases heat from both its north and south poles, suggesting a stable subsurface ocean conducive to life. The findings, published on November 7 in Science Advances, reveal unexpected thermal activity at the north pole. This balance of heat could sustain the moon's liquid water for billions of years.
Enceladus, one of Saturn's most intriguing moons, has long been a prime candidate for extraterrestrial life due to its global, salty ocean hidden beneath an icy surface. Scientists previously knew of heat loss at the south pole, where geysers eject water vapor and ice particles. However, a study by researchers from Oxford University, the Southwest Research Institute, and the Planetary Science Institute in Tucson, Arizona, has uncovered significant heat flow at the north pole as well.
Using data from NASA's Cassini spacecraft, the team analyzed the north polar region during the deep winter of 2005 and summer of 2015. Infrared observations from Cassini's Composite InfraRed Spectrometer (CIRS) showed the surface there was about 7 K warmer than expected, indicating heat leaking from the subsurface ocean at 0°C (32°F) through the icy crust to the frigid surface at -223°C (-370°F).
The measured heat flow at the north pole is 46 ± 4 milliwatts per square meter, contributing to a total of about 54 gigawatts across Enceladus—comparable to the output of 66 million solar panels or 10,500 wind turbines. This aligns with predictions from tidal heating caused by Saturn's gravity, maintaining a balance that keeps the ocean liquid over long periods.
"Enceladus is a key target in the search for life outside the Earth, and understanding the long-term availability of its energy is key to determining whether it can support life," said Dr. Georgina Miles, lead author from the Southwest Research Institute and University of Oxford.
The research also refined ice shell thickness estimates: 20 to 23 km at the north pole and 25 to 28 km on average. "Understanding how much heat Enceladus is losing on a global level is crucial to knowing whether it can support life," added Dr. Carly Howett, corresponding author from Oxford and the Planetary Science Institute. "It is really exciting that this new result supports Enceladus' long-term sustainability, a crucial component for life to develop."
These insights aid planning for future missions to explore the ocean, though the ocean's exact age remains uncertain.