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Detection of exospheric O 2 + at Saturn's moon Dione
Author(s) -
Tokar R. L.,
Johnson R. E.,
Thomsen M. F.,
Sittler E. C.,
Coates A. J.,
Wilson R. J.,
Crary F. J.,
Young D. T.,
Jones G. H.
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl050452
Subject(s) - exosphere , saturn , physics , ion , astrobiology , plasma , astronomy , energetic neutral atom , planet , quantum mechanics
During a close pass of Cassini through the plasma wake of Saturn's moon Dione on April 7, 2010 the Cassini Plasma Spectrometer (CAPS) detected molecular oxygen ions (O 2 + ) on pick up ring velocity distributions, thus providing the first in situ detection of a neutral exosphere surrounding the icy moon. The density of O 2 + determined from the CAPS data ranges from 0.01 to 0.09 /cm 3 and is used to estimate the exosphere O 2 radial column density, obtaining the range 0.9 to 7 × 10 11 /cm 2 . CAPS was unable to directly detect pick up H 2 O + from the exosphere but the observations can be used to set an upper limit to their density of ∼10 times the O 2 + density.