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Saturn's little moon with the big crater, Mimas (396 kilometers, 246 miles across), is the star of this movie which consists of 37 individual frames taken over 20 minutes, while Cassini remained sharply pointed at the icy worldlet. On the right-hand, or eastern, limb of the moon is the distinctive profile of the 130 kilometer (80 mile) –wide crater Herschel, for which Mimas is well-known (see PIA06582). The crater takes up a large portion of the moon’s surface and makes central part of the limb appear flattened from this viewing angle. Mimas appears to rotate very slightly this sequence of images, as the Sun-Mimas-spacecraft, or 'phase', angle changes from 87 to 88 degrees. Mimas always presents the same hemisphere toward Saturn so that, like our Moon, the length as its day is the same as the period it takes to orbit its planet (approximately 22.5 hours for Mimas). The images were taken in visible light with the narrow angle camera on February 20, 2005 from a distance of approximately 1.7 million kilometers (1.1 million miles) from Mimas. The image scale is approximately 10 kilometers (6 miles) per pixel. |