Publication Date:
2009-06-26
Description:
The discovery of water vapour and ice particles erupting from Saturn's moon Enceladus fuelled speculation that an internal ocean was the source. Alternatively, the source might be ice warmed, melted or crushed by tectonic motions. Sodium chloride (that is, salt) is expected to be present in a long-lived ocean in contact with a rocky core. Here we report a ground-based spectroscopic search for atomic sodium near Enceladus that places an upper limit on the mixing ratio in the vapour plumes orders of magnitude below the expected ocean salinity. The low sodium content of escaping vapour, together with the small fraction of salt-bearing particles, argues against a situation in which a near-surface geyser is fuelled by a salty ocean through cracks in the crust. The lack of observable sodium in the vapour is consistent with a wide variety of alternative eruption sources, including a deep ocean, a freshwater reservoir, or ice. The existing data may be insufficient to distinguish between these hypotheses.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schneider, Nicholas M -- Burger, Matthew H -- Schaller, Emily L -- Brown, Michael E -- Johnson, Robert E -- Kargel, Jeffrey S -- Dougherty, Michele K -- Achilleos, Nicholas A -- England -- Nature. 2009 Jun 25;459(7250):1102-4. doi: 10.1038/nature08070.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory for Atmospheric & Space Physics, University of Colorado, Boulder, Colorado 80309, USA. nick.schneider@lasp.colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19553993" target="_blank"〉PubMed〈/a〉
Keywords:
Exobiology
;
Gases/*chemistry
;
*Moon
;
Planets
;
Sodium/*analysis
;
Spectrum Analysis
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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