One of the biggest impact craters on the moon is mysteriously shaped like a three-ringed bull’s-eye. After decades of deliberation, scientists said they may have finally figured out how those rings came to be. The crater in question, called the Orientale impact basin, is located on the edge of the moon’s near side, so the feature is barely visible from Earth. The crater formed about 3.8 billion years ago. Three concentric rings circle the basin, the biggest of which measures nearly 580 miles (930 kilometers) across. These strange circles have lacked a solid explanation until now.
http://www.space.com/34529-moon-giant-bulls-eye-crater-mystery-solved.html
