Beneath the icy surface of Saturn's moon Enceladus, a hidden ocean of warmth and potential life may exist. New research from NASA's Cassini mission reveals that Enceladus, a prime candidate for extraterrestrial life, is releasing heat from both poles, suggesting a long-term thermal balance that could support life. This discovery challenges previous beliefs that heat loss was limited to the south pole, where geysers shoot water vapor and ice particles into space. The findings were published on November 7 in Science Advances.
A team of scientists from Oxford University, the Southwest Research Institute, and the Planetary Science Institute in Tucson, Arizona, has uncovered the first evidence of significant heat flow at Enceladus' north pole. This suggests that Enceladus generates and releases much more heat than a dormant, frozen moon would. Enceladus is a geologically active world with a global, salty ocean hidden beneath its icy surface, considered one of the most promising environments in the solar system for life beyond Earth.
For life to thrive, Enceladus' ocean must remain stable over long periods, maintaining an equilibrium between energy gained and lost. This balance is sustained through tidal heating, caused by Saturn's powerful gravitational pull. If too little heat is produced, Enceladus' surface activity would fade, and its ocean could eventually freeze. Too much energy, however, might trigger excessive geological activity, disrupting the delicate environment that supports its ocean.
The research team used data from NASA's Cassini spacecraft to study the north polar region during two key periods: the deep winter of 2005 and the summer of 2015. They found that the north pole's surface was roughly 7 K warmer than expected, indicating heat leaking upward from the hidden ocean. The team measured a heat flow of 46 ± 4 milliwatts per square meter, which equals about two-thirds of the average heat escaping through Earth's continental crust. This amounts to about 35 gigawatts of energy, roughly the power produced by 66 million solar panels or 10,500 wind turbines.
When the new measurements are combined with the heat previously detected at the active south pole, Enceladus' total heat loss reaches about 54 gigawatts, aligning closely with predictions of how much heat should be generated by tidal forces. This nearly perfect balance between heat creation and loss indicates that Enceladus' ocean could remain liquid for vast spans of time, offering a stable, long-term environment that might allow life to develop.
The next challenge for scientists is to determine how long Enceladus' ocean has been around. If it has existed for billions of years, the conditions for life would have been stable long enough for it to potentially emerge. However, the exact age of the ocean remains uncertain. The research also demonstrated that thermal readings can help estimate the thickness of Enceladus' ice shell, an important factor for planning future missions that may attempt to explore its ocean using robotic probes or landers.
The study highlights the need for long-term missions to ocean worlds that may harbor life, and the fact that data might not reveal all its secrets until decades after it has been obtained.
