Jupiter in the Ultraviolet: Acetylene and Ethane Abundances in the Stratosphere of Jupiter from Cassini Observations between 0.15 and 0.19 μm
Abstract
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 ± 0.07 ppm for acetylene and 20.8 ± 5.1 ppm for ethane. Finally, we perform a sensitivity study for the JUICE ultraviolet spectrograph, which has extended wavelength coverage out to 0.21 μm, enabling the retrieval of ammonia and phosphine abundances, in addition to acetylene and ethane.
- Publication:
-
The Astronomical Journal
- Pub Date:
- June 2020
- DOI:
- 10.3847/1538-3881/ab91a6
- arXiv:
- arXiv:2005.09895
- Bibcode:
- 2020AJ....159..291M
- Keywords:
-
- Jupiter;
- Ultraviolet astronomy;
- Planetary atmospheres;
- Outer planets;
- Solar system planets;
- Spectroscopy;
- 873;
- 1736;
- 1244;
- 1191;
- 1260;
- 1558;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for publication in The Astronomical Journal 28 pages, 23 figures, 3 tables