This plot shows results from Cassini's Ion Neutral Mass Spectrometer (INMS) and Cosmic Dust Analyzer (CDA), obtained during the spacecraft's close approach to Enceladus on July 14th, 2005.
Within a minute of closest approach to Enceladus, the two instruments aboard the Cassini spacecraft detected material coming from the surface of the moon. INMS measured a large peak in the abundance of water vapor at approximately 35 seconds before closest approach to Enceladus, as it flew over the south polar region at an altitude of 270 kilometers (168 miles).
The High Rate Detector (HRD) of the CDA observed a peak in the number of fine, powder-sized icy particles coming from the surface approximately a minute before reaching closest approach at an altitude of 460 kilometers (286 miles).
The character of these detections is very similar to the venting of vapor and fine, icy particles from the surfaces of comets when they are warmed by sunlight as they near the Sun. On Enceladus however, it is believed that internal heat, possibly from tidal forces, is responsible for the activity. The close but different occurrences of the two detections is yielding important clues to the location of the vents and even the venting process.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.