Look up on a clear night and you can see some circular formations on the face of our lunar neighbor. These are impact craters, circular depressions found on planetary surfaces.
Some 3.8 billion years ago, the moon was a dangerous place – constantly bombarded with asteroids and comets. Our celestial neighbour still bears the scars of this time, in the shape of craters. The biggest of these are called basins, and one is the mysterious, 930km-diameter Orientale Basin, which looks like a bull’s eye with three round rings around it.