Jupiter in the Ultraviolet: Acetylene and Ethane Abundances in the Stratosphere of Jupiter from Cassini Observations between 0.15 and 0.19μm
journal contributionposted on 2020-07-02, 10:27 authored by Henrik Melin, LN Fletcher, PGJ Irwin, SG Edgington
At wavelengths between 0.15 and 0.19 μm, the far-ultraviolet spectrum of Jupiter is dominated by the scattered solar spectrum, attenuated by molecular absorptions primarily by acetylene and ethane, and to a lesser extent ammonia and phosphine. We describe the development of our radiative transfer code that enables the retrieval of abundances of these molecular species from ultraviolet reflectance spectra. As a proof-of-concept we present an analysis of Cassini Ultraviolet Imaging Spectrograph (UVIS) observations of the disk of Jupiter during the 2000/2001 flyby. The ultraviolet-retrieved acetylene abundances in the upper stratosphere are lower than those predicted by models based solely on infrared thermal emission from the mid-stratosphere observed by the Composite Infrared Spectrometer (CIRS), requiring an adjustment to the vertical profiles above 1 mbar. We produce a vertical acetylene abundance profile that is compatible with both CIRS and UVIS, with reduced abundances at pressures $<$1 mbar: the 0.1 mbar abundances are $1.21 \pm 0.07$ ppm for acetylene and $20.8 \pm 5.1$ ppm for ethane. Finally, we perform a sensitivity study for the JUICE UVS instrument, which has extended wavelength coverage out to 0.21μm, enabling the retrieval of ammonia and phosphine abundances, in addition to acetylene and ethane.
This work is supported by a European Research Council Consolidator Grant under the European Unionʼs Horizon 2020 research and innovation program, grant agreement 723890 at the University of Leicester, by a Royal Society Research Fellowship, and by UK Science and Technology Facilities Council (STFC) grant ST/N000749/1. T
CitationAstronomical Journal , 2020
Author affiliationSchool of Physics and Astronomy
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