The Cassini Imaging Team discovered Methone (pronounced me-thoh-nee) on June 1, 2004. This tiny moon orbits between two of Saturn's mid-sized icy moons, Mimas and Enceladus, at a radius of about 194,000 kilometers (120,456 miles) from its planet. Astronomers have suggested two differing theories to explain the presence of Methone and two other small sister moons, Pallene and Anthe. The first theory indicates that the three little moons may have fragmented off of either Mimas or Enceladus. The second theory, on the other hand, suggests that all five moons--the three small moons and the two mid-size ones--may be the sad remnants of a larger menagerie of moons that floated around in that area--which is situated close to Saturn. Methone orbits its gigantic parent planet in 24 hours.
Cassini is an unmanned spacecraft sent to the Saturn system. It is the fourth space probe to visit the ringed planet, as well as the first to enter orbit. It has been studying Saturn and its many moons since arriving there in 2004.
The findings of the two missions are presented in papers published on April 13, 2017, by planetary scientists with NASA's Cassini mission to Saturn and the venerable Hubble Space Telescope (HST). In one of the papers, Cassini scientists announced their discovery that a form of chemical energy life can feed on appears to exist on Enceladus. In the second paper, HST researchers report additional evidence of plumes erupting from Jupiter's moon, Europa, whose fascinating frozen crust of ice resembles a cracked eggshell. It has long been recognized by planetary scientists that beneath Europa's bizarre cracked shell of ice, there is a sloshing global ocean of liquid water.