Cassini UVIS Detection of Saturn's North Polar Hexagon in the Grand Finale Orbits

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Keywords :

Saturn; hexagon; aurora; ultraviolet; haze; Cassini

Abstract :

[en] Cassini's final orbits in 2016 and 2017 provided unprecedented spatial resolution of Saturn's polar regions from near-polar spacecraft viewing geometries. Long-wavelength channels of Cassini's Ultraviolet Imaging Spectrograph instrument detected Saturn's UV-dark north polar hexagon near 180 nm at planetocentric latitudes near 75°N. The dark polar hexagon is surrounded by a larger, less UV-dark collar poleward of planetocentric latitude 65°N associated with the dark north polar region seen in ground-based images. The hexagon is closely surrounded by the main arc of Saturn's UV aurora. The UV-dark material was locally darkest on one occasion (23 January 2017) at the boundary of the hexagon; in most Ultraviolet Imaging Spectrograph images the dark material more uniformly fills the hexagon. The observed UV-dark stratospheric material may be a hydrocarbon haze produced by auroral ion-neutral chemistry at submicrobar pressure levels. Ultraviolet Imaging Spectrograph polar observations are sensitive to UV-absorbing haze particles at pressures lower than about 10-20 mbar.

Research Center/Unit :

STAR - Space sciences, Technologies and Astrophysics Research - ULiège

Disciplines :

Space science, astronomy & astrophysics

Author, co-author :

Pryor, W. R.; Department of Science, Central Arizona College, Coolidge, AZ USA

Esposito, L. W.; Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO USA

Jouchoux, A.; Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO USA

West, R. A.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA

Grodent, Denis ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)

Gérard, Jean-Claude ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)

Radioti, Aikaterini ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)

Lamy, L.; LESIA, Observatoire de Paris, PSL, CNRS, UPMC, Université Paris Diderot, Meudon, France

Koskinen, T.; Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ USA)

Language :

English

Title :

Cassini UVIS Detection of Saturn's North Polar Hexagon in the Grand Finale Orbits

Publication date :

01 July 2019

Journal title :

Journal of Geophysical Research. Planets

ISSN :

2169-9097

eISSN :

2169-9100

Publisher :

Wiley, Hoboken, United States - New Jersey

Volume :

124

Pages :

1979-1988

Peer reviewed :

Peer Reviewed verified by ORBi

Additional URL :

https://ui.adsabs.harvard.edu/abs/2019JGRE..124.1979P

Available on ORBi :

since 27 August 2019

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