Saturn’s icy moon Enceladus emits much more heat than would be expected if it were simply an inert body, reinforcing the hypothesis that it could harbor life.
MADRID, Nov. 7 (EUROPA PRESS).- New findings from the Cassini mission of the NASA show that Enceladusone of the moons of saturn and one of the main candidates for hosting extraterrestrial life, is losing heat from both poles, indicating that it has the long-term stability necessary for the development of lifeaccording to researchers from the Oxford University (United Kingdom), the Southwest Research Institute and the Tucson Planetary Science Institute (USA). The findings are published in Science Advances.
Specifically, the new study led has provided the first evidence of a flow of significant heat at Enceladus’ north pole, refuting previous assumptions that heat loss was limited to its active south pole. This finding confirms that the icy moon emits much more heat than would be expected if it were simply an inert body, reinforcing the hypothesis that could harbor life.
Enceladus is a very active world, with a global, salty subsurface ocean, which is believed to be the source of its heat. The presence of liquid water, heat, and the right chemicals (such as phosphorus and complex hydrocarbons) make its subsurface ocean one of the best places in our solar system for life to have evolved outside of Earth.
But this subsurface ocean can only support life if it has a stable environment, with a balance between energy losses and gains. This balance is maintained by tidal heating: Saturn’s gravity stretches and compresses the moon as it orbits, generating heat inside. If Enceladus does not receive enough energy, its surface activity would slow or cease, and the ocean could freeze. On the other hand, excess energy could cause an increase in ocean activity, altering its environment.
“Enceladus is a key target in the search for life beyond Earth, and understanding the long-term availability of its energy is critical to determining whether it can support life,” details Georgina Miles (Southwest Research Institute and visiting scientist at the Department of Physics at the University of Oxford), lead author of the article.
Until now, direct measurements of heat loss from Enceladus have only been made at the south pole, where spectacular plumes of ice and water vapor erupt from deep fissures in the surface. Instead, the north pole was believed to be geologically inactive.
Using data from NASA’s Cassini spacecraft, researchers compared observations of the north polar region in the middle of winter (2005) and summer (2015). These observations were used to measure how much energy Enceladus loses from its “warm” subsurface ocean (0°C, 32°F) as heat travels through its ice shell to the moon’s frigid surface (-223°C, -37°F) and then radiates into space.
By modeling expected surface temperatures during the polar night and comparing them with infrared observations from Cassini’s Composite Infrared Spectrometer (CIRS), the team found that the surface of the north pole was about 7 degrees Kelvin (K) warmer than predicted.
This discrepancy could only be explained by heat leakage from the underlying ocean. The measured heat flux (46 * 4 milliwatts per square meter) may seem small, but it represents about two-thirds of the heat loss (per unit area) through the Earth’s continental crust. Across the entire surface of Enceladus, this conductive heat loss amounts to about 35 gigawatts: approximately equivalent to the production of more than 66 million solar panels (with a power of 530 W) or 10,500 wind turbines (with a power of 3.4 MW).
When combined with heat escaping from Enceladus’ previously estimated active south pole, the moon’s total heat loss amounts to 54 gigawatts: a figure that closely matches the predicted heat input due to tidal forces. This balance between heat production and loss strongly suggests that Enceladus’s ocean can remain liquid over geological time scales, offering a stable environment where life could potentially emerge.
“Understanding how much heat Enceladus loses globally is crucial to knowing if it can support life,” says Dr. Carly Howett (Department of Physics, University of Oxford and Planetary Science Institute, Tucson, Arizona), lead author of the article. “It’s really exciting that this new result supports the long-term sustainability of Enceladus, a critical component for the development of life.”
According to the researchers, the next key step will be to determine whether Enceladus’s ocean has existed long enough for life to develop. At the moment, his age is still uncertain.
The study also showed that thermal data can be used to independently estimate the thickness of the ice sheet, an important parameter for future missions planning to explore Enceladus’s ocean, for example, using robotic landers or submersibles. The results suggest that the ice is between 20 and 23 km deep at the North Pole, with a global average of between 25 and 28 km, slightly higher than previous estimates obtained using other remote sensing and modeling techniques.
“Determining the subtle surface temperature variations caused by Enceladus’s conductive heat flow from its daily and seasonal temperature changes was challenging, and was only possible thanks to Cassini’s long missions,” adds Miles. “Our study underscores the need for long-term missions to ocean worlds that may harbor life, and the fact that the data may not reveal all its secrets until decades after it is obtained.”