Io at Sunset

How tall are mountains on Jupiter 's moon Io ? One way to find out is to view them at sunset . Tall structures facing the Sun are then better-lit and cast long shadows . The above image highlights Mongibello Mons on the far left, a sharp ridge rising so high it would rank among the highest mountains on Earth . The violently changing surface of Io shows not only classic volcano cinder cones but also many thrust faults where the ground has fractured and created dramatic shear cliffs . The grayscale image was taken two years ago by the robot spacecraft Galileo currently orbiting Jupiter .