Enceladus: Secrets of Saturn's Strangest Moon

Wrinkled landscapes and spouting jets on Saturn's sixth-largest moon hint at underground waters

[CASSINI GEYSER OBSERVATIONS] A thermal map shows temperatures up to 180 kelvins along the stripes, much too hot to be explained by solar heating. The jets originate in the very hottest regions (white circles). NASA/JPL/SPACE SCIENCE INSTITUTE
[CASSINI GEYSER OBSERVATIONS] The jets can be traced to specific locations on the tiger stripes. Oddly, these locations do not obviously differ from other parts of the stripes. NASA/JPL/SPACE SCIENCE INSTITUTE
[CASSINI GEYSER OBSERVATIONS] The jets feed Saturn's E ring, as Cassini saw from a distance of about two million kilometers. Some of the long, tendril-like structures seen in the vicinity of Enceladus are the extensions of the jets. Others are created by Enceladus's gravitational perturbations of passing particles in the E ring. NASA/JPL/SPACE SCIENCE INSTITUTE
[CASSINI GEYSER OBSERVATIONS] The tiny, icy grains sprayed into space are easiest to see when backlit by the sun. Mountains and valleys are visible along the edge of this silhouette. NASA/JPL/SPACE SCIENCE INSTITUTE
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[CASSINI SURFACE OBSERVATIONS] Close-up of the tiger-stripe region shows blocks of ice the size of houses (inset). Surrounding the stripes is a sinuous circumpolar chain of mountains that may be the Enceladan tectonic equivalent of the Himalaya. NASA/JPL/SPACE SCIENCE INSTITUTE
[CASSINI SURFACE OBSERVATIONS] On close inspection by Cassini, large regions on Enceladus that looked smooth to Voyager are actually highly textured (inset). Deep chasms extend northward into fractured terrains. Even craters are fractured, sliced and often degraded. NASA/JPL/SPACE SCIENCE INSTITUTE
[CASSINI SURFACE OBSERVATIONS] SOUTHERN HEMISPHERE of Enceladus was revealed by Cassini for the first time in 2005. This mosaic of images shows the surface as it would appear if our vision extended into the infrared and ultraviolet. (To the unaided eye, the surface looks uniformly white.) The "tiger stripes" near the bottom are warm, geologically active gashes across the south polar terrain. Their bluish colors arise because they are coated with larger than average ice grains that absorb infrared light. NASA/JPL/SPACE SCIENCE INSTITUTE
4 AS SEEN FROM CASSINI spacecraft, Enceladus slips in front of Dione, a larger and more distant moon whose gravity indirectly helps to drive Enceladus's activity. The outer part of Saturn's rings is in the foreground. NASA/JPL/SPACE SCIENCE INSTITUTE
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3 ENCELADUS (left of center) is a tenth the size of Saturn's largest moon, Titan. Bodies of its size lose their internal heat quickly; apart from Enceladus, they are all geologically dead. What keeps Enceladus active? NASA/JPL/SPACE SCIENCE INSTITUTE
2 FIRST FLYBY of Enceladus, by the Voyager 2 spacecraft in 1981, produced images of limited coverage and mediocre resolution. The smooth areas indicated geologic activity in the recent past. NASA/JPL/SPACE SCIENCE INSTITUTE
1 jets of steam and icy grains erupt from deep fractures in the south polar terrain of Enceladus, making this tiny body one of only four places in the solar system known to have geologic activity in the present day. This artist’s conception includes astronauts for scale. Ron Miller