A reanalysis of ISO-SWS Jupiter observations: preliminary results

Jupiter still has some unanswered questions regarding its formation history and atmospheric processes (Taylor et al., Cambridge Planetary Science, 2006). With this work, we hope to contribute to the progress of unravelling some of these questions.

We used the observations of Jupiter from the ESA mission Infrared Space Observatory (ISO) (Kessler et al., A&A 315, L27, 1996) in the 793.65-3125 cm^-1 (3.2-12.6 µm) region using the Short-Wave Spectrometer (SWS) (de Graauw et al, A&A 315, L49-L54, 1996). Our work is focused on the 793.65-1492.54 cm^-1 (6.7-12.6 µm) region of the spectrum. We argue that it warrants a revisit and reanalysis since it was an important step in the study of Jupiter’s atmosphere and there have been advancements in atmospheric models and line data, despite the age of this dataset.

Firstly, as a way to verify the validity of our method, we used the NEMESIS radiative transfer suite (Irwin et al., Journal of Quantitative Spectroscopy & Radiative Transfer 109, 1136–1150, 2008) to reproduce the results from Encrenaz et al., Planetary and Space Science 47, 1225-1242, 1999. This study is done using the CIRS NEMESIS template as a base adapted to the ISO-SWS data.  We use correlated k-tables compiled from line data from Fletcher et al., Nature communications 9.1, 1-14, 2018 for a NH₃, PH₃, ¹²CH₃D, ¹²CH₄, ¹³CH₄, C₂H₂, C₂H₆, He, H₂, C₂H₄ and C₄H₂ model atmosphere, with our results showing good agreement.

Having verified our method, we present here our preliminary results of the study of abundances of ¹²CH₃D, ¹²CH₄, ¹³CH₄, C₂H₂ and C₂H₆ of Jupiter’s atmosphere as well as our initial study of the pressure-temperature profile of Jupiter. We use the NEMESIS suite to determine the abundances as a function of altitude and retrieve the pressure-temperature profile. We compare our results with the profiles and abundances from Neimann et al., Journal of Geophysical Research Atmospheres 103(E10):22831-45, 1998 and Fletcher et al., Icarus 278, 128–161, 2016 with the aim to constrain the number of possible best fit profiles.

We also present our initial study the H/D and ¹²C/¹³C isotopic ratio of the Jovian atmosphere from the abundances of ¹²CH₃D, ¹³CH₄ and ¹²CH₄ following the methodology from Fouchet et al., Icarus 143, 223–243, 2000.

With this preliminary work we hope to further advance the knowledge about the chemical processes that happen in Jupiter, as well as the chemical and temperature vertical distribution. As future work, we expect to extend our frequency domain to the full range of ISO/SWS observations and study the ¹⁵N/¹⁴N ratio.

 

 

Acknowledgements

We thank Thérèse Encrenaz, from LESIA, Observatoire de Paris, for providing the data for this work and Patrick Irwin, from the University of Oxford (UK), for the help with the NEMESIS radiative transfer suite.

 

We acknowledge support from the Portuguese Fundação para a Ciência e a Tecnologia (FCT)/MCTES through the research grants UIDB/04434/2020, UIDP/04434/2020, (ref. PTDC/FIS-AST/29942/2017) through national funds and by FEDER through COMPETE 2020 (ref. POCI-01-0145 FEDER-007672) and through a grant of reference 2021.04584.BD.