One of the most beautiful scenes on the Moon is the graceful Sinus Iridium, Latin for "Bay of Rainbows." It is actually the relic of a huge crater 160 miles in diameter. After this crater formed, a much larger impact excavated a basin called Mare Imbrium (Sea of Storms). The missing half of Sinus Iridium was probably destroyed in the impact. About 3.1 billion years ago, long after the impacts, lava from the Moon's interior flooded the Imbrium Basin and filled the remaining half of Sinus Iridium.
The rugged hills around Sinus Iridium are called the Jura Mountains, after a mountain range on Earth on the border between France and Switzerland. Unlike terrestrial mountains, lunar mountains are not created by plate tectonics and erosion. Instead, they are the rims of huge impact craters.
Created 17 December 2007, Last Update 25 May 2011
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