Enceladus is the sixth biggest moon of Saturn. The moon that was discovered by William Herschel in 1789 is named after the giant Enceladus of Greek mythology. It won't live up to its name when it comes to size. With a diameter of 500 km, the moon would fit within the north sea. But it will live up to its name when it comes to being one of the strongest candidates for finding non-terrestrial microbial life in our Solar system. Studies have shown half of Earth's biomass lives long under the surface. As microbial life is not just a surface phenomenon the chances of finding this kind of organism outside the so-called goldilocks zone of a star increases. The strongest candidates are moons around gas giants that under their thick icy surface has oceans heated with volcanic activity. One of those candidates is Jupiter's moon Europa that I wrote about in this . And the other is Enceladus.
Image credit: NASA/JPL-Caltech
On January 16th, 2005 Nasa's probe Cassini's was on a flyby pass Saturn when it captured a very unusual event on Enceladus. There was a bright light coming from the south pole of the moon shining out into space. There were enormous geysers plumbing out vapor into space, more than 8000 times larger than geyser on Earth. Nasa immediately decided that Cassini should have a new mission. To study Enceladus. The probe was reprogrammed from earth to fly into these plumbs and find out was the vapor was made of. It took three years of reprogramming until Cassini was able to do that and the result showed that the vapor was liquid water. Some of the water will fall back on Enceladus as snow but the most will make of the material in Saturn's E ring. The result also showed that the water contains salt which is a very important ingredient for life. The chemicals in the water were very similar to earth and it also showed that something inside Enceladus was heating the water. On June 27, 2018, scientists reported the detection of complex organics compounds from the Cassini data. The Cassini mission ended in September 2017 with the probe crashing into Saturn's atmosphere.
It is very hard getting a probe to investigate Enceladus within a reasonable budget. Several future missions to Enceladus that have been proposed has been canceled. Here is are a list of candidates that are under study and could be our next mission to the icy moon: