Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure

J. Hunter Waite*, Michael R. Combi, Wing Huen Ip, Thomas E. Cravens, Ralph L. McNutt, Wayne Kasprzak, Roger Yelle, Janet Luhmann, Hasso Niemann, David Gell, Brian Magee, Greg Fletcher, Jonathan Lunine, Wei Ling Tseng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

538 Citations (Scopus)


The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (<1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby.

Original languageEnglish
Pages (from-to)1419-1422
Number of pages4
Issue number5766
Publication statusPublished - 2006 Mar 10
Externally publishedYes

ASJC Scopus subject areas

  • General


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