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Janus Hides in Plain Sight
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Janus Hides in Plain Sight

August 23, 2006

Tiny, dust-sized particles in Saturn's rings become much easier to see at high phase angle -- the angle formed by the Sun, the rings and the spacecraft. The brightest ring at the right is the F ring; the next feature to the left is the outer edge of the A ring. Inward of that, and very bright, are the ringlets in the Encke gap.

Epimetheus (116 kilometers, or 72 miles across) is easy to spot just right of the outer F ring edge. Janus (181 kilometers, or 113 miles across), however, is quite a bit harder to make out; it is the dark spot located directly to the left of Epimetheus, above the gap between the A and F rings.

Within the space between the A and F rings there are two faint rings seen previously by the Cassini spacecraft. The inner faint ring (called R/2004 S1) coincides with the orbit of Atlas. The outer one forms the inner boundary of the orbit of Prometheus.

The narrow G ring is visible above and below the bright F ring.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 15, 2006 at a distance of approximately 2.7 million kilometers (1.7 million miles) from Epimetheus and 2.8 million kilometers (1.7 million miles) from Janus. The view was acquired at a Sun-Epimetheus-spacecraft, or phase, angle of 164 degrees. Image scale is 16 kilometers (10 miles) per pixel.