Abstract
Abstract Due to its proximity to Earth, Jupiter of the solar system serves as a unique case study for gas-giant exoplanets. In the current Letter, we perform fits of ab initio, reflective, semi-infinite, homogeneous model atmospheres to 61 phase curves from 0.40 to 1.00 μm, obtained from the Cassini spacecraft, within a Bayesian framework. We reproduce the previous finding that atmospheric models using classic reflection laws (Lambertian, Rayleigh, single Henyey–Greenstein) provide poor fits to the data. Using the double Henyey–Greenstein reflection law, we extract posterior distributions of the single-scattering albedo and scattering asymmetry factors and tabulate their median values and uncertainties. We infer that the aerosols in the Jovian atmosphere are large, irregular, polydisperse particles that produce strong forward scattering together with a narrow backscattering lobe. The near-unity values of the single-scattering albedos imply that multiple scattering of radiation is an important effect. We speculate that the observed narrow backscattering lobe is caused by coherent backscattering of radiation, which is usually associated with solar system bodies with solid surfaces and regolith. Our findings demonstrate that precise, multiwavelength phase curves encode valuable information on the fundamental properties of cloud/haze particles. The method described in this Letter enables single-scattering albedos and scattering asymmetry factors to be retrieved from James Webb Space Telescope phase curves of exoplanets.
Highlights
Named after the Roman god of the sky and thunder, Jupiter is the most massive planet of our Solar System, has been studied for several centuries and was the subject of close scrutiny by recent space missions (Porco et al 2004; Bolton et al 2017)
We speculate that the observed narrow backscattering lobe is caused by coherent backscattering of radiation, which is usually associated with Solar System bodies with solid surfaces and regolith
The method described in this Letter enables single-scattering albedos and scattering asymmetry factors to be retrieved from James Webb Space Telescope phase curves of exoplanets
Summary
Named after the Roman god of the sky and thunder, Jupiter is the most massive planet of our Solar System, has been studied for several centuries and was the subject of close scrutiny by recent space missions (Porco et al 2004; Bolton et al 2017). The visible and near-infrared phase curves of Jupiter are of particular interest, because they quantify the fraction of sunlight reflected by the Jovian atmosphere as a function of the orbital phase angle. Using data from the Cassini space mission, Dyudina et al (2016) and Mayorga et al (2016) previously showed that the Jovian phase curves are “cuspy” and peak more sharply towards zero phase angle than classic laws of reflection (Lambertian, Rayleigh).
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