Publication Date:
2006-03-11
Description:
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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waite, J Hunter Jr -- Combi, Michael R -- Ip, Wing-Huen -- Cravens, Thomas E -- McNutt, Ralph L Jr -- Kasprzak, Wayne -- Yelle, Roger -- Luhmann, Janet -- Niemann, Hasso -- Gell, David -- Magee, Brian -- Fletcher, Greg -- Lunine, Jonathan -- Tseng, Wei-Ling -- New York, N.Y. -- Science. 2006 Mar 10;311(5766):1419-22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16527970" target="_blank"〉PubMed〈/a〉
Keywords:
Ammonia/analysis
;
Atmosphere
;
Carbon Dioxide/analysis
;
Evolution, Planetary
;
*Extraterrestrial Environment/chemistry
;
Mass Spectrometry
;
Methane/analysis
;
*Saturn
;
Spacecraft
;
Water/analysis
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
