Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure |
| |
Authors: | Waite J Hunter Combi Michael R Ip Wing-Huen Cravens Thomas E McNutt Ralph L Kasprzak Wayne Yelle Roger Luhmann Janet Niemann Hasso Gell David Magee Brian Fletcher Greg Lunine Jonathan Tseng Wei-Ling |
| |
Institution: | Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA. |
| |
Abstract: | 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. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|