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Fig. 1
This is a spacecraft image, showing an eclipse of a small icy moon of Saturn known as Enceladus.
Credit: NASA/JPL-Caltech/Space Science Institute
NASA recently published a wonderful image of two Saturnian moons, acquired by the Saturn-orbiting Cassini spacecraft. The moons are Enceladus, a small geologically active moon, and Titan, Saturn’s largest moon. Intriguingly, Enceladus (504 km across), shining above center, is partially eclipsed by the immense shadow of its giant parent planet. Titan (5,150 km across) is the pale apparently smaller object to the right.
When the photo was taken, the Cassini probe was at a distance of about 26,000 km from Enceladus and 1.1 million km from Titan. In 2005, Cassini discovered large plumes of icy material and cold vapors erupting from Enceladus into space. This is a rare type of volcanic activity, known as ice volcanoes or cryovolcanoes. Enceladus is therefore one of few Solar System objects, including Earth, which show ongoing volcanic activity.
In Fig. 1, Saturn projects its shadow across Enceladus’ lower half. The image was taken in visual light, with Cassini’s wide-angle camera, on 1 October 2011.
The Cassini spacecraft is a joint project of NASA, the European Space Agency, ESA, and the Italian Space Agency (ASI). It was placed into Saturn orbit in July 2004, to study the planet and its large family of moons. Cassini has acquired thousands of images, and conducted numerous startling discoveries that revolutionized scientists’ understanding of the magnificent Saturn system.
References:
NASA
www.nasa.gov/
NASA’s Photojournal
Further Reading
http://saturn.jpl.nasa.gov
Titan Eclipsed by Saturn
http://photojournal.jpl.nasa.gov/catalog/PIA11508