Some 3.8 billion years ago, the moon was a dangerous place \u2013 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\u2019s eye with three round rings around it.<\/p>\n
Scientists have long tried to work out what what happened during the violent event that caused the Orientale Basin, but it\u2019s proven rather difficult. But new data and models<\/a> from the NASA GRAIL<\/a> (Gravity Recovery and Interior Laboratory) spacecraft has finally started to unveil the truth. This spacecraft flew just two kilometres above the crater\u2019s surface, giving researchers a chance to look at it with a resolution never achieved before.<\/p>\n The \u201cheavy bombardment\u201d era of the moon actually affected all bodies in the solar system. However, very large impacts were comparatively rare at this time and we therefore have only a few examples to study for details of their formation. The Orientale Basin on the moon is one, and the much smaller Chixculub Impact Crater<\/a> on Earth is another.<\/p>\n If you want an image of what happens during large impacts and have a full cup of tea nearby, you can do the following experiment. Drip a single drop of tea from a spoon held at some height above the cup into the tea and watch the circular ripples this causes. Then repeat the experiment and watch from the side. Can you spot the \u201chill\u201d that shoots up at the point of impact? Many things happen too fast to observe with the unaided eye, and high speed cameras would be required to capture the process fully.<\/p>\nThe science of rings<\/h2>\n