2006/03/09 by J. H. Waite, M. R. Combi, W.-H. Ip +11 · 13 citations
Physics and Astronomy · Chemistry · #Astro and Planetary Science #Planetary Science and Exploration #Astrophysics and Star Formation Studies #Enceladus #Plume #Saturn #Atmospheric sciences #Mass spectrometry #Ion #Icy moon #Methane #Astrobiology #Chemistry #Environmental science #Astrophysics #Physics #Meteorology
paper · doi:10.1126/science.1121290
openalex publication_date 2006/03/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
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.