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Exospheric signatures of alkali abundances in Europa's regolith
Author(s) -
Cipriani F.,
Leblanc F.,
Witasse O.,
Johnson R. E.
Publication year - 2009
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 - 10.1029/2009gl038636
Subject(s) - regolith , potassium , exosphere , astrobiology , sodium , alkali metal , physics , astrophysics , galilean , orbiter , analytical chemistry (journal) , mineralogy , chemistry , astronomy , ion , environmental chemistry , classical mechanics , quantum mechanics , organic chemistry
The sodium and potassium exospheres of Europa are described as well as the variations of the Na/K ratio from Europa's surface up to about 20 Europa radii. Observations carried out by M. E. Brown (2001) are used to constrain the Na and K source terms. We find that an average source rates ratio of 17 ± 2 at the surface and loss rates ratio of 26 ± 2 reproduce well the observations. These values are consistent with the conclusions by R. E. Johnson et al. (2002) on its most probable origin. Moreover, we here show that a local increase of the surface Na/K ratio by a factor 2 in a 20° × 30° wide region should induce an observable exospheric signature between 80 and 300 km above the surface. Therefore simultaneous observations of sodium and potassium from an Europa orbiter would allow one to derive important properties of the surface and subsurface of the Galilean moon.