Jupiter's Dark Side - April 9, 2007
During its seven-day orbit, Jupiter’s moon Ganymede ducks behind its host planet and hides from astronomers on Earth. Though a speck next to the gas giant, Ganymede is our solar system’s largest moon, larger than the planet Mercury. It is made of rock and ice, and has noticeable impact craters. Visible in this natural-color Hubble image is Ganymede’s surface as well as Jupiter's Great Red Spot, a storm the size of two Earths that has been raging for more than 300 years.