The Solar System


What is Jupiter’s moon Ganymede like?

Ganymede is the largest moon in the solar system, about one-and-a-half times the diameter of Earth’s Moon. It has a very thin atmosphere and its own magnetic field. Measurements taken by the Galileo spacecraft showed atomic hydrogen gas escaping from Ganymede’s surface; and other measurements made using the Hubble Space Telescope showed excess oxygen on the surface of Ganymede’s thick icy crust. Scientists think that the hydrogen and oxygen may come from molecules of frozen water ice on Ganymede’s surface, which are then broken up into their component atoms by radiation from the Sun. These and other observations suggest that, like Europa, Ganymede may also have a vast underground sea of water.


This is a web preview of the "The Handy Astronomy Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App