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!
Galilean Moons Of Jupiter. One dark, clear January night in 1610, Galileo Galilei climbed to the roof of his house in Padua. He looked up at the sky that was speckled with the flickering fires of a multitude of starry objects, and then aimed his small, primitive "spyglass"--which was really one of the first telescopes--up at that star-blasted sky above his home. Over the course of several such starlit, clear winter nights, Galileo discovered the four large Galilean moons that circle around the largest planet in our Sun's family, the enormous, gaseous world, Jupiter. This intriguing quartet of moons--Io, Europa, Ganymede, and Callisto--were named for four of the numerous mythic lovers of the King of the Roman gods.
Earlier theories suggested that the craggy outline of a region of the lunar surface, named Oceanus Procellarum--or the Ocean of Storms--had resulted from a large asteroid impact. If this theory had been correct, the basin it had dug out would represent the largest asteroid impact basin scarring the lunar surface. However, mission scientists, scrutinizing GRAIL data, now believe that they have discovered new evidence that the craggy outline of this rectangular region--approximately 1,600 miles across--was actually caused by the formation of ancient rift valleys.