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A virtual tour of the Galilean Satellites

Galileo's imagination was quick to comprehend the importance of the 4 starry objects he observed near Jupiter in January 1610, not only for himself as a scientist but for our common understanding of the place of the Earth and our species in the cosmos. Even he, however, could not have imagined what those four objects would actually look like once humans got their first good look. Some 369 years the fast traveling Voyager 1 and 2 spacecraft provided that first good look during 1979, followed by an even closer look from the Galileo Orbiter beginning in 1996 through 2001. The following mosaics represent some of the best of those views. They include views of impact craters young and ancient, icy terrains that have been intensely faulted, eroded or disrupted, mountains towering 10 or more kilometers high, and volcanic eruptions hotter than those on Earth. Each of the four Galilean satellites is geologically distinct, betraying very diverse global histories and evolutions. Images and other observations of these 4 objects revealed the importance of tidal heating and subsurface water oceans in planetary evolution, but mapping is very incomplete. New missions to explore these planetary bodies are being planned and the images and observations of the missions that went before will lay the groundwork for these new explorations as we begin the 5th Galilean century.