7 January 1610
A Revolutionary Day
On a cold winters night in January of 1610 at his home in Padova, Northern Italy, Galileo pointed a telescope at the planet Jupiter for the first time and became the first human to see objects in orbit about another celestial object. These were the four planet-sized moons orbiting Jupiter, each similar in size to our own Moon or larger. It did not take Galileo very long to understand the importance (both to human evolution and to himself) of the 4 "stars" close to Jupiter he had discovered during his first observations of that planet in the cool italian winter of 1610. Indeed, as December 1609 drew to close, noone suspected that their universe was about to undergo a revolutionary change, but Galileo's discovery that January of 4 objects orbiting an object other than Earth (together with the phases of Venus) signaled the end of the Earth-centered view of the Universe.
A Second Galilean Revolution
Not even Galileo, however, could conceive of the true nature of these four planet-like bodies and the role gravity has played in their history (Galileo had some knowledge on this subject having also conducted simple experiments to test the nature of gravity). For 370 years, however, the nature of these moons remained largely unknown to us. At that point, two robot voyagers and a larger robotic "Galileo" came along to explore these 4 moons in earnest, and even learned scientists of our own time were not prepared for what they saw, including volcanoes on Io and subsurface oceans on Europa and the other icy satellites. What these spacecraft saw proved to be a second Galilean revolution, in our understanding of how planets operate and the (perhaps) universality of habitable environments in our universe.
Galileo at 400 Years: Looking Ahead
Four hundred years after Galileo ushered in a new era, serious plans are in preparations for a robotic return to the dynamic Jupiter system, with a focus on the large ice-rich moons Europa and Ganymede. As part of the special anniversary celebration, Cambridge University Press and Dr. Paul Schenk and pleased to announce the pending release of the Atlas of the Galilean Satellites. This is the first truly comprehensive Atlas and compendium of maps of these satellites ever compiled (details on the other pages). This volume will be of prime importance for those planning the next phase of exploration of Jupiter and its large planetary moons in the next decade and beyond.