First discovered in 1789, Enceladus is the sixth-largest moon of Saturn, a sizable distinction for a planet that has sixty-two known moons of which only fifty-three are officially named.
Previous data from NASA’s Cassini spacecraft in 2005 showed “eruptions of water geysers” at the surface of Enceladus suggesting that the moon might have water beneath its frozen crust, likely in an area surrounding its core. Because the presence of water serves as a kind of litmus test for the potential of life in space, scientists dubbed the moon, “one of the best potential sites for hosting life in the solar system” along with the moon Mimas and Titan.
Now, a new report published in the March 12th issue of the prestigious journal Nature, takes Cassini’s previous findings further. According to the authors, detected “grains [of] nanometer-sized SiO2 (silica) particles, [were] initially embedded in icy grains emitted from Enceladus’ subsurface waters and released by sputter erosion.” Moreover, they determined that because of the composition and size of the particles, they would have to come from “high-temperature (>90 degrees C) hydrothermal reactions” capable of quickly transporting products from the ocean floor to approximately 24 miles above. As reported by Space.com, this mechanism is similar to the action of hydrothermal vents on Earth’s seafloor and thus, Enceladus now has the distinction of being the first location outside of earth where scientists have detected ongoing hydrothermal activity.
To arrive at their conclusion, the team of scientists used computer models to determine the path of the silica grains. Their models showed that the particles likely came from Saturn’s E ring; however, Saturn’s E ring is made up of mostly small ice grains and so the scientists realized that “the source of the particles in the E ring [was] Enceladus.”
Lab tests then confirmed that these particles could only be generated under very specific physical conditions, namely very high temperatures, depths of at least 24 miles and a pH greater than 8.5.
Interestingly, the localization of the first non-Earth hydrothermal vent proved surprising to the authors. As lead author Hsiang-Wen Sean Hsu said in a statement, “It is the existence of high-temperature rock-water reactions at the present time that surprises me the most, as we would expect Enceladus to be a frozen world…It means that there is still a big knowledge gap in understanding how solar system bodies evolve.”
Hsu continued that the main source of heat is likely an effect known as “tidal heating.” In the case of Enceladus, Saturn’s gravitational pull so deforms the moon that rocks are heated, though to generate the high levels of heat predicted to be at Enceladus’ core, there must be another source of heat, potentially a radioactive material.
This finding is sure to increase interest in Enceladus as a potential harbor for life. In his statement, Hsu mentions that hydrothermal systems fulfill three criteria to sustain life, namely they produce energy, nutrients and liquid water. Surprisingly, we might come closer to finding life in space by examining extreme areas of the solar system, so unlike our own.
(Photo courtesy of NASA)