Vertical Structure and Color of Jovian Latitudinal Cloud Bands during the Juno Era

Emma K. Dahl,Erandi A. Wijerathna,James A. Sinclair,Nancy J. Chanover,Patrick G. J. Irwin,Glenn S. Orton,Paul D. Strycker,David G. Voelz,Kevin H. Baines

doi:10.3847/psj/abd400

Abstract

Abstract The identity of the coloring agent(s) in Jupiter’s atmosphere and the exact structure of Jupiter’s uppermost cloud deck are yet to be conclusively understood. The Crème Brûlée model of Jupiter’s tropospheric clouds, originally proposed by Baines et al. and expanded upon by Sromovsky et al. and Baines et al., presumes that the chromophore measured by Carlson et al. is the singular coloring agent in Jupiter’s troposphere. In this work, we test the validity of the Crème Brûlée model of Jupiter’s uppermost cloud deck using spectra measured during the Juno spacecraft’s fifth perijove pass in 2017 March. These data were obtained as part of an international ground-based observing campaign in support of the Juno mission using the New Mexico State University Acousto-optic Imaging Camera at the 3.5 m telescope at Apache Point Observatory in Sunspot, NM, USA. We find that the Crème Brûlée model cloud-layering scheme can reproduce Jupiter’s visible spectrum both with the Carlson et al. chromophore and with modifications to its imaginary index of refraction spectrum. While the Crème Brûlée model provides reasonable results for regions of Jupiter’s cloud bands such as the North Equatorial Belt and Equatorial Zone, we find that it is not a safe assumption for unique weather events, such as the 2016–2017 Southern Equatorial Belt outbreak that was captured by our measurements.

Highlights

Jupiter’s atmosphere is a dynamic, variable, and complicated system (Ingersoll et al 2004; West et al 2004)
Regardless, we found that the CB model was able to reproduce these longitudinally dependent North Equatorial Belt (NEB) spectra very well at both emission zenith angles, and we did not find the same discrepancy with the blue slope of the spectrum as Braude et al (2020)
It should be noted that while the extrapolated absorption of the Carlson et al (2016) chromophore extends to 350 nm and our New Mexico State University Acoustooptic Imaging Camera (NAIC) wavelength range stops at 470 nm, we found that our sensitivity to the location of the shoulder of the chromophore absorption and its slope was sufficient to interpret our results since the slope of the Carlson et al (2016) chromophore is close to linear shortwards of 500 nm

Summary

Introduction

Jupiter’s atmosphere is a dynamic, variable, and complicated system (Ingersoll et al 2004; West et al 2004). The measurements made by the Juno spacecraft since its arrival at Jupiter in 2016 July have wholly recontextualized the Jovian atmosphere, magnetosphere, interior, and system as a whole (Bolton et al 2017, 2019). The location and composition of Jupiter’s tropospheric cloud layers, while difficult to measure directly, have been predicted through the use of thermochemical equilibrium models. These models use temperature–pressure profiles, chemical abundances, chemical reaction paths, and temperature- and pressure-dependent reaction rates to predict the depths at which certain species will condense. Ammonium hydrosulfide, and ammonia have been predicted to condense into Jovian clouds at approximately 6, 2.2, and 0.7 bar, respectively (Lewis 1969; Weidenschilling & Lewis 1973; Atreya et al 1999)

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Conclusion