Abstract:
:A plume of water vapour escapes from fissures crossing the south polar region of the Saturnian moon Enceladus. Tidal deformation of a thin surface crust above an internal ocean could result in tensile and compressive stresses that would affect the width of the fissures; therefore, the quantity of water vapour released at different locations in Enceladus' eccentric orbit is a crucial measurement of tidal control of venting. Here we report observations of an occultation of a star by the plume on 24 October 2007 that revealed four high-density gas jets superimposed on the background plume. The gas jet positions coincide with those of dust jets reported elsewhere inside the plume. The maximum water column density in the plume is about twice the density reported earlier. The density ratio does not agree with predictions-we should have seen less water than was observed in 2005. The ratio of the jets' bulk vertical velocities to their thermal velocities is 1.5 +/- 0.2, which supports the hypothesis that the source of the plume is liquid water, with gas accelerated to supersonic velocity in nozzle-like channels.
journal_name
Naturejournal_title
Natureauthors
Hansen CJ,Esposito LW,Stewart AI,Meinke B,Wallis B,Colwell JE,Hendrix AR,Larsen K,Pryor W,Tian Fdoi
10.1038/nature07542subject
Has Abstractpub_date
2008-11-27 00:00:00pages
477-9issue
7221eissn
0028-0836issn
1476-4687pii
nature07542journal_volume
456pub_type
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