Analysis of gaseous ammonia (NH3) absorption in the visible spectrum of Jupiter - Update

Abstract

An analysis of currently available ammonia (NH 3 ) visible-to-near-infrared gas absorption data was recently undertaken by Irwin et al. (Icarus, 302 (2018) 426) to help interpret Very Large Telescope (VLT) MUSE observations of Jupiter from 0.48 -0.93 µm, made in support of the NASA/Juno mission. Since this analysis a newly revised set of ammonia line data, covering the previously poorly constrained range 0.5 -0.833 µm, has been released by the ExoMol project, "C2018" , which demonstrates significant advantages over previously available data sets, and providing for the first time complete line data for the previously poorly constrained 5520-and 6475-Å bands of NH 3 . In this paper we compare spectra calculated using the ExoMol-C2018 data set with spectra calculated from previous sources to demonstrate its advantages. We conclude that at the present time the ExoMol-C2018 dataset provides the most reliable ammonia absorption source for analysing low-to medium-resolution spectra of Jupiter in the visible/near-IR spectral range, but note that the data are less able to model high-resolution spectra owing to small, but significant inaccuracies in the line wavenumber estimates. This work is of significance not only for solar system planetary physics, but for future proposed observations of Jupiter-like planets orbiting other stars, such as with NASA's planned Wide-Field Infrared Survey Telescope (WFIRST). Subject headings: planets and satellites: atmospheres -planets and satellites: individual (Jupiter) Yurchenko 2012; Tennyson et al. 2016). The new line list covers an extended wavelength

The 2020 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

“…CoYuTe, which also uses MARVEL energy levels [188] , is both more accurate and more extensive than the BYTe line list [179] it replaces. In particular, CoYuTe was found to provide a good model of the Jovian optical absorption spectrum due to ammonia [34] although with a shift in positions of the main bands. More laboratory work or analysis of existing laboratory work on the visible spectrum of ammonia will be required to resolve this issue.…”

“…In addition the ExoMol database has been used to support a variety of other studies. Examples including the analysis of gaseous ammonia in Jupiter [34] , tentative detection of H 2 S in Uranus [35] , detection of CaO in meteors [36] and SiO in B[e] Supergiants [37] , Late-type stars [38] or circumstellar environment [39] . Detections in the atmospheres of exoplanets are discussed below.…”

Colour and tropospheric cloud structure of Jupiter from MUSE/VLT: Retrieving a universal chromophore

“…Each absorption band was approximated with a Goody-Voigt band model (Goody and Yung, 1995), and then k-tables computed through exponential line fitting (Irwin et al, 2018). Ammonia absorption data were obtained from the new Coles et al (2018) line list, with k-distributions computed as in Irwin et al (2019a). The presence of hydrogen gas in Jupiter also induces substantial absorption around 810-830 nm, primarily due to collision-induced absorption (CIA) of H 2 -He and H 2 -H 2 , which we modelled according to Borysow and Frommhold (1989) and Borysow et al (2000) respectively, as well as some additional, very narrow quadrupole absorption lines for which we used the line lists found in the HITRAN database (Rothman et al, 2013).…”

The ExoMol project: An update

“…This illustrates the iterative nature by which line lists can be improved. One interesting early application of the CoYuTe line list was made by Irwin et al (2019) who used the preliminary, room temperature version (see Fig. 2) to analyse the visible absorption spectrum of gaseous ammonia in of Jupiter; a region not addressed by the earlier BYTe line list.…”