It was 400 years ago today that Galileo discovered smaller planets attending the planet Jupiter. Jason Perry is doing a far better job than I could of writing about the momentous discovery on his blog, the Gish Bar Times. This post serves as an index to his thoroughly researched history, and he's also maintaining an index to other bloggers' writings on the topic here.
In addition to Jason, I also want to highlight the ongoing work of Paul Schenk, who will soon be publishing an Atlas of the Galilean Satellites. He's been studying outer planet moons -- more specifically, the topography of outer planet moons (and what that says about their geology) -- since the 1980s. While in Padua for an event celebrating the anniversary, he uploaded a bunch of spectacular 3D flyovers of the Galilean moons to his Youtube channel; numerous screen grabs from his movies can be viewed at his blog, Dr. Schenk's 3D House of Satellites. My favorites include this one, showing a nine-kilometer-high mountain peak next to a caldera on Io:
Tohil Mons, Io Paul Schenk generated this 3D flyover of Tohil Mons, a nine-kilometer-high mountain peak next to a caldera on Io.Video: NASA / JPL-Caltech / Paul Schenk
Eroded plains of Callisto Paul Schenk generated this 3D flyover of the rumpled, peaky terrain of Callisto's plains.Video: NASA / JPL-Caltech / Paul Schenk
Both are vertically exaggerated, the Callisto one much more than the Io one.