Exploration Fortuitously, Cassini flew through this gas cloud during the July 14 encounter, allowing instruments like the Ion and Neutral Mass Spectrometer ( INMS ) and the cosmic dust analyzer (CDA) to directly sample the plume. INMS measured the composition of the gas cloud, detecting mostly water vapor, as well as minor components like molecular nitrogen , methane , and carbon dioxide .  CDA "detected a large increase in the number of particles near Enceladus," confirming the satellite as the primary source for the E ring.  Analysis of the CDA and INMS data suggest that the gas cloud Cassini flew through during the July encounter, and observed from a distance with its magnetometer and UVIS, was actually a water-rich cryovolcanic plume, originating from vents near the south pole.  Visual confirmation of venting came in November 2005, when ISS imaged geyser-like jets of icy particles rising from the moon's south polar region. 
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.