Reference : Hubble Space Telescope Observations of Variations in Ganymede's Oxygen Atmosphere and...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/223813
Hubble Space Telescope Observations of Variations in Ganymede's Oxygen Atmosphere and Aurora
English
Molyneux, P. M. [Southwest Research Institute > > > >]
Nichols, J. D. [University of Leicester > > > >]
Bannister, N. P. [University of Leicester > > > >]
Bunce, E. J. [University of Leicester > > > >]
Clarke, J. T. [Boston University > > > >]
Cowley, S. W. H. [University of Leicester > > > >]
Gérard, Jean-Claude mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO) >]
Grodent, Denis mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) >]
Milan, S. E. [University of Leicester > > > >]
Paty, C. [Georgia Institute of Technology, Atlanta, GA, USA > > > >]
30-Apr-2018
Journal of Geophysical Research. Space Physics
Wiley
123
Yes (verified by ORBi)
International
2169-9380
2169-9402
Hoboken
NJ
[en] Ganymede ; Atmosphere ; Aurora
[en] We present high‐sensitivity Hubble Space Telescope (HST) Cosmic Origins Spectrograph and HST Space Telescope Imaging Spectrograph measurements of atmospheric OI 130.4‐nm and OI] 135.6‐nm emissions at Ganymede, which exhibit significant spatial and temporal variability. These observations represent the first observations of Ganymede using HST Cosmic Origins Spectrograph and of both the leading and trailing hemispheres within a single HST campaign, minimizing the potential influence of long‐term changes in the Jovian plasma sheet or in Ganymede's atmosphere on the comparison of the two hemispheres. The mean disk‐averaged OI] 135.6‐nm/OI 130.4‐nm observed intensity ratio was 2.72 ± 0.57 on the leading hemisphere and 1.42 ± 0.16 on the trailing hemisphere. The observed leading hemisphere ratios are consistent with an O2 atmosphere, but we show that an atomic oxygen component of ~10% is required to produce the observed trailing hemisphere ratios. The excess 130.4‐nm emission on the trailing hemisphere relative to that expected for an O2 atmosphere was ~11 R. The O column density required to produce this excess is determined based on previous estimates of the electron density and temperature at Ganymede and exceeds the limit for an optically thin atmosphere. The implication that the O atmosphere is optically thick may be investigated in future by observing Ganymede as it moves into eclipse or by determining the ratio of the individual components within the 130.4‐nm triplet.
Space sciences, Technologies and Astrophysics Research - STAR
Researchers ; Professionals
http://hdl.handle.net/2268/223813
10.1029/2018JA025243
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JA025243
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