Enceladus likely has vents and a vast ocean that may support life.
Move over Europa, another outer solar system moon is now in the spotlight as a potential harbour for extraterrestrial life. NASA scientists have discovered strong evidence that Saturn’s moon Enceladus not only has a massive sub-surface ocean, but also its bottom is warmed by hydrothermal vents, which on Earth are oases for complex life. These findings make Enceladus one of the strongest candidates for hosting life in our solar system, which create another target for future space missions seeking to discover life.
A team led by researchers from the Laboratory for Atmospheric and Space Physics at the University of Colorado analyzed data collected from NASA’s Cassini-Huygens spacecraft to make the discovery. They used Cassini-Huygens’s Cosmic Dust Analyzer to examine the dust that makes up Saturn’s E ring, a belt of Saturn’s iconic giant ring made of ice and dust that originates from Enceladus. They discovered two types of particles that indicate the moon has a warm ocean deep below its icy surface: sodium-rich ice grains and silicon dioxide. Sodium-rich ice grains would only form from liquid water that was in contact with rock, and silicon dioxide would only form in water temperatures above 90 degrees Celsius. The study was published on March 12 in the journal Nature.
Discovering silicon dioxide in Saturn’s ring led the researchers to conclude the ocean floors of Enceladus likely have hydrothermal vents, as this compound is created in these vents on Earth. Hydrothermal vents form when ocean water percolates into rock and gets superheated by geothermal activity, spouting back into the ocean at near-boiling temperatures and rich in chemical nutrients. On Earth, hydrothermal vents support a rich ecosystem based solely of bacteria that grow directly from the chemicals they spout. Because they occur too deep in Earth’s oceans for light to reach, hydrothermal vents are the only known ecosytems that exist entirely independent of the sun, and are considered potential sites for life’s beginning on this planet. This discovery makes Enceladus the only known body other than Earth to have hydrothermal vents.
Astronomers have suspected Enceladus might harbour an ocean since 2005, when NASA’s Cassini spacecraft captured images of giant icy geysers erupting from the moon’s surface. Last April, researchers led by an astronomer from the University of Rome confirmed that Enceladus has a 30 to 40-kilometer deep ocean based on observations of its gravity field from the Cassini-Huygens spacecraft. Aspects of the silicon dioxide particles discovered in the most recent study also concluded that the moon has a 40-kilometer deep ocean.
Enceladus is one of Saturn’s 62 known moons, and it is the sixth largest at one-seventh the diameter of Earth’s moon. The discovery of this evidence indicates the moon has hydrothermal vents and a warm ocean. It now makes Enceladus of comparable interest to Jupiter’s moon, Europa, in the search for life in our solar system. Europa has attracted widespread interest as a possible beacon of life since evidence was discovered that it had an ocean similar to Enceladus’s under a frozen surface, even becoming the subject of a science fiction movie, The Europa Report.