Saturn's largest and second largest moons, Titan and Rhea, appear to be stacked on top of each other in this true-color scene from NASA's Cassini spacecraft released on Dec. 23, 2013. The north ...

An image from Cassini of Saturn's icy moon Rhea A mystery on Saturn’s moon Rhea may have finally been solved. When NASA’s Cassini spacecraft flew past the planet’s second-largest moon before ...