Page 19 - Curriculum Visions Dynamic Book

The Galilean satellites
The Galilean satellites, Io, Europa, Ganymede, and Callisto, have been an intense source of curiosity for hundreds of years. Callisto and Ganymede are as big as the planet Mercury. But it was the Voyager missions in 1979 that first showed them to be some of the most spectacular bodies in the solar system—and showed that they were each completely different and unique. Europa, for example, is coated with ice, which may cover a liquid ocean. Io is the most active volcanic body we know about in the solar system. Both
Io and Europa are denser than Callisto and Ganymede. These outer bodies must be made up of at least half water.
condensation The change of state from a gas or vapor to a liquid.
galilean satellites The four
large satellites of Jupiter discovered by astronomer Galileo Galilei in 1610. They are Callisto, Europa, Ganymede, and Io.
galileo A U.S. space probe launched in October 1989 and designed for intensive investigation of Jupiter.
satellite An object that is in an orbit around another object, usually a planet.
voyager A pair of U.S. space probes designed to provide detailed information about the outer regions of the solar system.
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