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Enceladus is one of the most interesting worlds in our solar system. It is a moon of Saturn with a surface comprised entirely of bright ice. Why is the ice so reflective? Because it is constantly replenished from a subsurface ocean of salt water, which gushes through cracks in the surface as geysers.<\/p>\n
That is intriguing enough, but the implications are even more interesting – most significantly, there is liquid water beneath the frozen surface of Enceladus. Liquid water means a couple of things. First, it means the core of Enceladus is warm. The moon is not frozen solid through. A moon that size should have frozen solid by now, so there must be some source of energy keeping it warm.<\/p>\n
The first thought was that tidal forces from Saturn were responsible, but scientists could not make computer models fit. However, a 2017 paper hypothesized<\/a> that the core of Enceladus may be porous, and this model works. The core flexes, grinding rocks together, creating heat through friction. Further, liquid water would seep into the porous rock, heat to near boiling (90 C) and then rise to the surface and gush out through cracks. Heating would be greatest at the poles, and this is therefore also where the ice is thinnest. The model fits our observations.<\/p>\n Further, ice spewing from Enceladus appears to be responsible for Saturn’s E ring. The Cassini probe gave us a close-up view of the E ring, and according to JPL<\/a>:<\/p>\n The E ring is mostly made of ice droplets, but among them are peculiar nanoparticles. Cassini detected these passing silica nanograins, which can only be generated where liquid water and rock interact at temperatures above 90 degrees Celsius (about 200 degrees F). This points to hydrothermal vents deep beneath Enceladus\u2019 icy shell, not unlike the hydrothermal vents that dot the ocean floor here on Earth.<\/p><\/blockquote>\n That fits the new model too. All of this has astronomers interested in finding the signs of life outside of Earth very excited. Enceladus has a subsurface ocean of warm salty water. Sure, in some parts it’s really warm, but in others, farther from the pole, it may be just right.<\/p>\n Cassini found more than silica nanograins in the geysers of Enceladus and E ring of Saturn – it found simple organic molecules. In this context “organic” simply means containing carbon. Organic molecules, of course, are the basis for life, getting scientists even more excited. So we have water, heat, minerals, and organic molecules. It’s looking pretty good for critters crawling around beneath the surface of Enceladus.<\/p>\n