Ganymede: The Largest Moon

Explanation: What does the largest moon in the Solar System look like? Jupiter 's moon Ganymede , larger than even Mercury and Pluto , has an icy surface speckled with bright young craters overlying a mixture of older, darker, more cratered terrain laced with grooves and ridges. The large circular feature on the upper right, called Galileo Regio , is an ancient region of unknown origin . Ganymede is thought to have an ocean layer that contains more water than Earth and might contain life . Like Earth's Moon, Ganymede keeps the same face towards its central planet, in this case Jupiter. The featured image was taken about 20 years ago by NASA's Galileo probe , which ended its mission by diving into Jupiter's atmosphere in 2003. Currently, NASA's Juno spacecraft orbits Jupiter and is studying the giant planet's internal structure, among many other attributes.