Among the ringed gas giant planet Saturn's amazing collection of 62 diverse, bizarre, and beautiful moons and moonlets, sometimes one of them just seems to stand out in the crowd. Such a moon is little Methone. Looking like a shiny white egg in Space, and composed of very lightweight fluffy stuff, Methone is less dense than any other known moon or asteroid in our Solar System. In March 2013, astronomers announced at the 44th Lunar and Planetary Science Conference held in the Woodlands, Texas, that this strange little 5-kilometer-size moon is one of a batch of Space eggs in orbit around Saturn!
Ganymede: Ganymede is both the largest moon of Jupiter, our Solar System's planetary behemoth, as well as the largest moon in our entire Solar system. Observations of Ganymede by the HST in 2015 suggested the existence of a subsurface saline ocean. This is because patterns in auroral belts and rocking of the magnetic field hinted at the presence of an ocean. It is estimated to be approximately 100 kilometers deep with a surface situated below a crust of 150 kilometers.
A Moon Made Of Lightweight Fluff! Methone is small and oval--and unlike other tiny objects, composed of rock and ice, that scurry around our Solar System. Methone, which was observed up close for the very first time in 2012, is not pockmarked by impacts like other worldlets of its kind. Instead, this strange little moon, is very smooth--it shows not a hill nor an impact crater anywhere on its weirdly smooth surface. This shiny, white, icy egg in Space, residing in a peaceful nest of ice crystals, is an enigma wrapped in a bewildering mystery that some astronomers may have solved. The answer to the bewitching riddle of Methone? It is composed of lightweight fluff!