An assessment and test of Enceladus as an important source of Saturn's ring atmosphere and ionosphere

Wei-Ling Tseng, Wing Huen Ip

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The existence of an oxygen exosphere and ionosphere in Saturn's main ring region has been confirmed by the Saturn Orbital Insertion (SOI) observations of the Cassini spacecraft. Through the ion-molecule collisions, the ring atmosphere could serve as a source of O2+ ions throughout Saturn's magnetosphere. If photolysis of ice in the main rings is the dominant source of O2, then the complex structure of the ring atmosphere/ionosphere and the injection rate of neutral O2 will be subject to modulation by the seasonal variation of Saturn along its orbit (Tseng, Wei-Ling, Ip, W.-H., Johnson, R.E., Cassidy, T.A., Erlod, M.K. [2010]. Icarus 206, 382-389). In addition, the radio and plasma wave science (RPWS) instrument onboard Cassini found that a large amount of the Enceladus-originated water-group plasma would be deposited on the outer edge of the A ring (Farrell, W.M., Kaiser, M.L., Gurnett, D.A., Kurth, W.S., Persoon, A.M., Wahlund, J.E., Canu, P. [2008]. Geophys. Res. Lett. 35, L02203). A large amount of Enceladus' plume neutrals (water-group neutrals) would collide with the main rings through collisional interaction with the ambient neutrals and plasma ions (Jurac, S., Richardson, J.D. [2007]. Geophys. Res. Lett. 34, L08102; Cassidy, T.A., Johnson, R.E. [2010]. Icarus, in press). These absorbed ions and neutrals could be recycled to neutral oxygen molecules via grain-surface chemistry to contribute the ring oxygen atmosphere. In this work, we have examined the mass budget of the ring oxygen atmosphere of Saturn taking into account such an " exogenic" source. The maximum O2 source rate from recycling of Enceladus-originated plasma and neutrals is probably comparable or higher to the one from photolytic decomposition of ices. In the above case, the neutral O2 source rate would be independent of the solar insolation angle. Therefore, even at Saturn's Equinox, the extended oxygen atmosphere still could be an important supplier of oxygen ions in the saturnian magnetosphere. We have performed several studies for different recycling source rates from Enceladus. These predictions need further the Cassini Plasma Spectrometer (CAPS) and the Magnetospheric Imaging Instrument (MIMI) observations to be verified in future.

Original languageEnglish
Pages (from-to)294-299
Number of pages6
JournalIcarus
Volume212
Issue number1
DOIs
Publication statusPublished - 2011 Mar 1

Fingerprint

Enceladus
Saturn rings
Saturn
ionospheres
ionosphere
atmospheres
oxygen
atmosphere
rings
plasma
ion
magnetosphere
recycling
magnetospheres
ice
ions
photolysis
insolation
exosphere
test

Keywords

  • Enceladus
  • Magnetospheres
  • Rings

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

An assessment and test of Enceladus as an important source of Saturn's ring atmosphere and ionosphere. / Tseng, Wei-Ling; Ip, Wing Huen.

In: Icarus, Vol. 212, No. 1, 01.03.2011, p. 294-299.

Research output: Contribution to journalArticle

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