Enceladus

**Enceladus**, discovered in 1789 by William Herschel, is the sixth-largest moon of Saturn.  Until the two *Voyager* spacecraft and *Pioneer 11* passed near it in the early 1980s, very little was known about this small moon besides the identification of water ice on its surface. The Voyagers showed that Enceladus is only 500 kilometers in diameter and reflects almost 100% of the sunlight that strikes it. *Voyager 1* found that Enceladus orbited in the densest part of Saturn's diffuse E ring, indicating a possible association between the two, while *Voyager 2* revealed that despite the moon's small size, it had a wide range of terrains ranging from old, heavily cratered surfaces to young, tectonically-deformed terrain.

The *Cassini* spacecraft of the mid- to late 2000s acquired additional data on Enceladus, answering a number of the mysteries opened by the *Voyager* spacecraft and starting a few new ones. *Cassini* performed several close flybys of Enceladus in 2005, revealing the moon's surface and environment in greater detail. In particular, the probe discovered a water-rich plume venting from the moon's south polar region. This discovery, along with the presence of escaping internal heat and very few (if any) impact craters in the south polar region, shows that Enceladus is geologically active today. Moons around gas giants are typically more active, and warmer than one might otherwise expect, because of the significant tidal forces and magnetic disruption produced by orbiting such large bodies so closely.

Enceladus is one of only three outer solar system bodies (along with Jupiter's moon Io and Neptune's moon Triton) where active eruptions have been observed. Analysis of the outgassing suggests that it originates from a body of sub-surface liquid water, which along with the unique chemistry found in the plume, has fueled speculations that Enceladus may be important in the study of astrobiology.  The discovery of the plume has added further weight to the argument that material released from Enceladus is the source of the E-ring.

## External Links

* General information
	+ Calvin Hamilton's Enceladus page
	+ The Nine Planets: Enceladus
	+ The Planetary Society: Enceladus information
	+ CHARM: Cassini-Huygens Analysis and Results from the Mission page, contains presentations on recent Enceladus results
	+ Cassini Mission Enceladus Page. Contains catalog of released Cassini Images of Enceladus

* Images
	+ Catalog of NASA images of Enceladus
	+ Small Bodies Atlas: Enceladus. Phil Stooke's Atlas page for Enceladus containing a catalog of Voyager Enceladus images as well as maps based on Voyager Images
	+ Enceladus Basemap from Voyager and Cassini images

* Press releases
	+ JPL: Saturn's Moons Titan and Enceladus Seen by Cassini
	+ JPL: Cassini Finds an Atmosphere on Saturn's Moon Enceladus
	+ JPL/Univ. of Chicago: Cassini Finds Particles Near Saturn's Moon Enceladus
	+ NASA/JPL/CICLOPS: Cassini Finds Recent and Unusual Geology on Enceladus
	+ NASA/JPL: Cassini Finds an Active, Watery World at Saturn's Enceladus
	+ NASA/JPL: Cassini Finds Enceladus Tiger Stripes are Really Cubs
	+ SSI/UM/Max Planck: Cassini Findings Suggest Complex Story of Venting at the South Pole of Enceladus
	+ NASA/JPL/CICLOPS: NASA's Cassini Images Reveal Spectacular Evidence of an Active Moon
	+ NASA/JPL: Multiple Cassini Instruments Capture Enceladus Plume
	+ CICLOPS: Press Release: Cassini Images Of Enceladus Suggest Geysers Erupt Liquid Water At The Moon’s South Pole
	+ NASA/JPL: NASA's Cassini Discovers Potential Liquid Water on Enceladus
	+ LANL: Cassini measures geysers of Saturn's moon Enceladus
	+ Max Planck/APL/Imperial College: A Little Moon of Saturn Makes its Presence Known
	+ Max Planck: Volcanoes on Saturn’s Moon Enceladus
	+ JPL/UCSC/Univ. of Colorado: NASA-funded Study Says Saturn's Moon Enceladus Rolled Over

* News articles
	+ NOVA article `Life on a Tiny Moon'
	+ BBC Article Saturn's moon 'best bet for life'
	+ Images show Enceladus is a 'geologist's paradise' from New Scientist
	+ BBC article on atmosphere
	+ Liquid water on Saturn moon could support life
	+ BBC: Saturn moon 'may have an ocean'
	+ Commentary: Why Enceladus discovery matters (James Oberg, MSNBC)
	+ Encore For Enceladus! Saturn Moon Ripe For Astrobiology Exploration (Leonard David, Space.com)

## See also

* Europa
* Category:Moons of Saturn
* Saturn

## References

1. ↑ Planetary Body Names and Discoverers. Retrieved March 22, 2006.
2. ↑ Cassini Images Of Enceladus Suggest Geysers Erupt Liquid Water At The Moon’s South Pole. Retrieved March 22, 2006.