Janus, Prometheus and the Rings

A pair of Saturn's small, icy satellites accompany the planet's rings in this Cassini spacecraft snapshot.

Janus (179 kilometers, or 111 miles across) is farthest from Cassini here and occupies the top of the image. Prometheus (86 kilometers, or 53 miles across) orbits between the main rings and the thin F ring. The rings are between Janus and Prometheus. This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on April 9, 2010. The view was acquired at a distance of approximately 1 million kilometers (621,000 miles) from Prometheus and at a Sun-Prometheus-spacecraft, or phase, angle of 65 degrees. The view was acquired at a distance of approximately 1.1 million kilometers (684,000 miles) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 65 degrees. Image scale is about 6 kilometers (4 miles) per pixel on Prometheus and about 7 kilometers (4 miles) per pixel on Janus.

Photo credit: NASA/JPL/Space Science Institute