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Space Topics: Saturn

PAN (S/1981 S13)

The Encke Gap Moon

Pan in the Encke gap
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Pan in the Encke gap
Cassini snapped a series of images of Pan on June 7, 2005, from a distance of about 420,000 kilometers. Pan orbits within the Encke gap, within Saturn's A ring. Source Credit: NASA / JPL / SSI / Emily Lakdawalla

Size: Roughly 20 kilometers
Orbital radius: 133,583 kilometers - 2.22 Saturn radii - within the Encke gap in the A ring
Orbital period: 0.575 days - about 1/28 of Titan’s
Discovery: 1990 by Mark R. Showalter

Pan orbits within the Encke gap, inside Saturn’s A ring. However, Pan wasn't discovered by taking images of this gap -- it was discovered because its tiny gravitational tugs cause wave patterns in the A ring.  From the wave patterns, scientists deduced the existence of a ring, and discovered it by returning to Voyager images of the rings.  Images that Cassini captured during its closest-ever approach to the rings, when it was entering Saturn orbit, show stunning details in the density waves raised by Pan on the inner edge of the Encke gap.