Enceladus: Saturn’s Icy Moon With a Hidden Ocean and Potential for Life
- Saturn's icy moon Enceladus harbors a subsurface liquid water ocean beneath a shell of ice measuring 19 to 25 miles thick, according to a study published on April...
- The discovery confirms longstanding suspicions that began when NASA's Cassini spacecraft first spotted ice and water vapor spewing from fractures near the moon's south pole in 2005.
- The structural profile of Enceladus differs markedly from other icy ocean worlds in the solar system, such as Europa.
Saturn’s icy moon Enceladus harbors a subsurface liquid water ocean beneath a shell of ice measuring 19 to 25 miles thick, according to a study published on April 3 in the journal Science. Researchers determined that the regional sea sits above a rocky seafloor and holds enough water to cover an area at least as large as Earth’s Lake Superior, raising new possibilities for habitable environments in the solar system.
Gravity Measurements Reveal Enceladus Hidden Mass Anomaly
The discovery confirms longstanding suspicions that began when NASA’s Cassini spacecraft first spotted ice and water vapor spewing from fractures near the moon’s south pole in 2005. To map the interior, study lead author Luciano Iess of Sapienza University in Rome and his colleagues measured how the 313-wide moon tugged on the spacecraft during three close flybys conducted from 2010 to 2012. As co-author Sami Asmar of NASA’s Jet Propulsion Laboratory explained, As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we’re trying to measure.
Ground stations tracked changes in radio frequency to detect velocity shifts as small as one foot per hour.
That ultra-precise tracking system revealed a negative mass anomaly at the south pole, meaning the region held less mass than expected for a spherical body. While a large surface depression marked the area, the observed mass anomaly was significantly smaller than expected for that dent. Researchers concluded that denser liquid water underground must offset the missing surface mass. The main implication is that there are potentially habitable environments in the solar system in places which are completely unexpected,
Luciano Iess stated in an institutional video, noting that surface temperatures hover around minus 292 degrees Fahrenheit.
Comparing Enceladus and Europa Crustal Thickness
The structural profile of Enceladus differs markedly from other icy ocean worlds in the solar system, such as Europa. At Enceladus’s south pole, the ice shell above the hidden ocean may be only one to five kilometers thick, contrasting sharply with Europa’s estimated 29-kilometer ice crust. Furthermore, spacecraft exploring Enceladus may not need to drill through the shell at all because the moon naturally blasts material from its internal ocean straight into space through long fractures known as tiger stripes. Internal heating keeps the water liquid despite the frigid surface conditions. Tidal interactions between Enceladus and Dione, another of Saturn’s moons, help generate this internal energy. A previous 2011 study found that the south polar region of Enceladus pumps out 15.8 gigawatts of heat-generated power, an output equivalent to roughly 20 coal-fired power plants. Because the liquid water ocean remains in direct contact with a rocky seafloor, it theoretically permits the kinds of complex chemical reactions that supported the rise of life on Earth.
