Saturn's moon Mimas, as imaged by the Cassini spacecraft. It was discovered on 17 September 1789 by English astronomer William Herschel, and was named after Mimas, a son of Gaia in Greek mythology, by Herschel's son John. The large Herschel Crater is the dominating feature of the moon. With a diameter of 396 km (246 mi), it is the smallest astronomical body that is known to be rounded due to self-gravitation.Photo: NASA/JPL/SSI
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