A Giant Among Moons

Jupiter's Largest Moon
Ganymede as seen by New Horizons

The largest of Jupiter’s 63 known moons and the largest moon in our solar system, Ganymede has twice the mass of our own moon and is even larger than the planet Mercury. Its surface is marked by dark regions which are  full of craters and lighter areas lined with ridges.

This image was taken by the New Horizons spacecraft’s Long Range Reconnaissance Imager (LORRI) in February 2007 while on its way to Pluto. New Horizons is scheduled to pass by Pluto in 2015…it is still en route and is currently between the orbits of Saturn and Uranus, over 1.2 billion miles from Earth.

Ganymede has a thin oxygen atmosphere as well as a magnetosphere, and is the only moon currently known to have one. It is likely generated by a molten core made up of heavy conductive metals.

Discovered in 1610, Ganymede is easily visible from Earth as one of the four Galilean moons seen alongside Jupiter. All that’s needed is a small telescope or decent pair of binoculars mounted on a stand and a clear night sky.

Image: NASA/JHU/APL