Credit: NASA/JPL/Space Science Institute

Saturn is a ringed giant planet that dominates a mini solar system of moons, rings and one artificial satellite, the Cassini spacecraft. This magnificent image, acquired by Cassini, shows a Saturnian moon, and the shadow of another, cast upon the orb of the planet.

The bizarre moon Mimas (397 km across) is visible at upper left as point source of light. The shadow of Enceladus (504 km across), Saturn’s geologically-active moon, appears as a dark dot on Saturn’s colorful cloud bands, but Enceladus itself is not visible in the picture.

Saturn’s graceful rings also cast their immense shadows upon Saturn, and block sunlight from the low latitudes of the planet’s northern hemisphere.

On 30 June 2008, Cassini will complete its primary four-year mission to Saturn, but a two-year mission extension was approved in April 2008. Therefore, on 1 July 2008, the Saturn orbiter will begin its new mission, termed the Cassini Equinox Mission, as Saturn will pass its northern vernal equinox, which marks the beginning of spring in the northern hemisphere of Satrun, during this mission extension.

The ring shadows will drift past the planet's equator and into the southern hemisphere as Saturn passes through its northern vernal equinox on 11 August 2009, and the Sun moves northward through the ring plane.

This view looks down on the dark side of the rings, from about 22 degrees above the ring plane. This natural color image was composed by combining images taken in red, green and blue filters. The images were acquired with the Cassini spacecraft wide-angle camera on 16 December 2007, at a distance of approximately 1.4 million km from Saturn. Image scale is 86 km per pixel.

Further Reading

The Cassini-Huygens Mission to Saturn
http://saturn.jpl.nasa.gov/home/index.cfm

Aymen Mohamed Ibrahem
Senior Astronomy Specialist