Enceladus [en-SELL-ah-dus] is one of the innermost moons of Saturn. It is quite similar in size to Mimas, but has a smoother, brighter surface. Enceladus reflects almost 100 percent of the sunlight that strikes it. Unlike Mimas, Enceladus displays at least five different types of terrain. Parts of Enceladus shows craters no larger than 35 km in diameter. Other areas show regions with no craters, indicating major resurfacing events in the geologically recent past. There are fissures, plains, corrugated terrain and other crustal deformations. All of this indicates that the interior of the moon may be liquid today, even though it should have frozen aeons ago. It is postulated that Enceladus is heated by a tidal mechanism similar to Jupiter's moon Io. Enceladus is perturbed in its orbit by Saturn's gravitational field and by the large neighboring satellites Tethys and Dione.
Because Enceladus reflects so much sunlight, the surface temperature is only -330 degrees Fahrenheit (-201degrees Celsius).
Since early 2005, the Cassini-Huygens Mission to Saturn has uncovered many mysteries about Enceladus. Below is a discovery timeline for this intriguing moon.
February and March 2005
Enceladus has an atmosphere:
The Cassini spacecraft makes two trips by Enceladus.
- Cassini's magnetometer discovers an atmosphere around Enceladus, evidence that gases may be originating from the moon's surface or interior.
- The cosmic dust analyzer records thousands of hits from tiny particles of dust or ice, possibly coming from a cloud around the moon or from the adjacent E ring.
- The science teams plan to go back for a closer look.
Warm fractures on Enceladus:
Cassini flies within 175 km (109 miles) of Enceladus, the closest it comes to any of Saturn's moons.
- The imaging team sees unusual geology on the moon's southern pole, including house-sized ice boulders and evidence of recent geological activity.
- The visual and infrared mapping spectrometer determines that the large dark cracks, called "tiger stripes," at the south pole are very young and seem to have a continual supply of fresh ice.
- The composite infrared spectrometer shows that the south pole is much warmer than expected, suggesting an internal heat source.
- The ion and neutral mass spectrometer and the ultraviolet imaging spectrograph detect water vapor in the atmosphere, which appears to come from a localized source.
- The cosmic dust analyzer detects a large increase in the number of particles near Enceladus, confirming that Enceladus is the source of Saturn's E ring.
Spray above Enceladus:
- Cassini's visual and infrared mapping spectrometer measures the spectrum of the plumes originating from the south pole of the icy moon, capturing a very clear signature of small ice particles.
- The imaging team produces the first pictures of the plume of icy material streaming from Enceladus' south pole, possible evidence of Yellowstone-like geysers fed by reservoirs of liquid water.