A Giant Among Moons


Our solar system’s largest moon, Ganymede. © Ted Stryk.

With so much focus these days on Saturn’s many varied moons, I thought I’d post a beautiful image of Jupiter’s lesser-seen – but anything but lesser-sized – moon, Ganymede.

The largest of Jupiter’s 63 named moons – as well as the largest moon in our solar system – Ganymede has twice the mass of our moon and is even larger than the planet Mercury. At 3,280 miles wide Ganymede is nearly as large as Mars! Its surface is marked by dark regions which are  full of craters and lighter areas lined with grooves and ridges. Ganymede has a thin oxygen atmosphere as well as a magnetosphere. It is likely generated by a molten core made up of heavy conductive metals.

This image was taken by the Galileo spacecraft on February 27, 1997 and color-processed by Ted Stryk. It is currently featured on his blog Planetary Images from Then and Now.

Discovered in 1610, Ganymede is visible from Earth as one of the four Galilean moons seen alongside Jupiter (with Callisto, Io and Europa). All that’s needed is a small telescope or decent pair of binoculars mounted on a stand and a clear night sky…right now, with Jupiter so visible in the northern night sky, Ganymede can easily be seen with just a small amount of magnification.

Read more about Ganymede on The Planetary Society’s blog.

Image: NASA / JPL. Processed by Ted Stryk.