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Detection of Negative Pickup Ions at Saturn's Moon Dione
Author(s) -
Nordheim T. A.,
Wellbrock A.,
Jones G. H.,
Desai R. T.,
Coates A. J.,
Teolis B. D.,
Jasinski J. M.
Publication year - 2020
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 - 10.1029/2020gl087543
Subject(s) - exosphere , pickup , ion , saturn , physics , ionization , mass spectrometry , plasma , astrobiology , astronomy , atomic physics , astrophysics , planet , nuclear physics , quantum mechanics , artificial intelligence , computer science , image (mathematics)
We investigate a possible negative ion feature observed by the Cassini Plasma Spectrometer (CAPS) during a flyby of Saturn's moon Dione that occurred on 7 April 2010. By examining possible particle trajectories, we find that the observed particles are consistent with negative pickup ions originating near the moon's surface. We find that the mass of the negative pickup ions is in the range of 15–25 u and tentatively identify this species as O − , likely resulting from ionization and subsequent pickup from Dione's O 2 ‐CO 2 exosphere. Our estimates show that the negative ion density is ~3 × 10 −3 cm −3 . This is comparable to, but slightly smaller than, that previously reported for the density of O 2 + pickup ions for the same flyby, indicating that negative pickup ions may represent a major loss channel for Dione's exosphere.