The Cassini-Huygens exploration of Saturn, a seven-year joint venture of NASA, the European Space Agency, and the Italian Space Agency, is realizing more surprising discoveries. The Cassini space probe achieved its closest approach of any Saturn moon with a 109 mile orbit of one of the most innermost moons of Saturn, Enceladus on November 26, 2005.
Enceladus is a small moon of 314 miles across that is so bright it reflects nearly one hundred percent of its heat. For this reason, it is a very cold moon, with a temperature of minus 330 degrees Fahrenheit. Its orbit is influenced under the large gravitational pull of Saturn as well as the gravitational influence of large nearby moons Tethys and Dione. Previous voyages by Voyager as well as Cassini have shown it to have at least five different geological terrains across its small surface.
What was discovered that makes Enceladus so unique for such a cold moon is that unlike nearby moon Mimas, which is basically a completely dead moon, Enceladus is currently geologically active. An emission of water vapor and minute ice particles from its south pole from some sort of internal heat source on Enceladus has been confirmed. The cause of the tremendous heat source that must be present to heat the ice of such a cold moon to emit such a plume of ice and water vapor into the atmosphere is unkown. On its nearest approach to Enceladus of 109 miles, Cassini was able to use infrared detection to prove the existence of this column of ice into the atmosphere and beyond.
Saturn's E ring is the broadest and faintest of any of Saturn's rings. It is composed of fine ice particles of 2.9 microns in average size. The average size of Cassini's emissions is 10 microns. The tiniest particles escaping from Enceladus are the source of the composition of Saturn's E ring. This was a major discovery in itself.
Cassini confirmed that the heat sources are coming from geological phenomena known as the tiger stripes of Enceladus. The tiger stripes are parallel fissures running down the planet approximately eighty miles long and separated by twenty-five miles on average. They seem to be extremely geologically young being of between 10 and 1000 years old. At their southern end Cassini detected the large emanations of heat that are responsible for the ice particle ejections.
The cause of the internal heating remains the big mystery. It is surmised that it is due to tidal activity or possibly radioactive phenomena. This riddle regarding Enceladus is not yet understood as of today. Enceladus is one of the rare geologically active moons found so far in the solar system along with Jupiter's Io and Neptune's moon Triton.
More light will be shed on Enceladus in March of 2008 when Cassini revisits Enceladus.
1) Enceladus Erupting – A Nasa Report – 12-7-05
2) Enceladus Plume – Jet Propulsion Laboratory – 12-6-05
3) Possible Source of E Ring – Bill Arnett – 2-17-05
4) Saturn: Moons: Enceladus – Nasa: Solar Systems Exploration – 10-6-03
5) Enceladus's Tiger Stripes are Really Cubs – Nasa Release
M.S. Physics - University of Minnesota
B.S. Computer Science - University of Oregon
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