Formation Constraints on Jupiter’s Great Red Spot chromophore from Microphysical Modelling

The composition and formation mechanisms of the compounds responsible for the reddish colouration of Jupiter’s Great Red Spot (GRS) – the so-called chromophores – remain unknown. In recent years, the laboratory-produced chromophore proposed by Carlson et al. (2016) has been shown to satisfactorily reproduce the observed visible spectra not only of the GRS but also of various regions across Jupiter’s disk, with little to no modification (Sromovsky et al., 2017; Baines et al., 2019; Pérez-Hoyos et al., 2020; Braude et al., 2020; Dahl et al., 2021; Fry & Sromovsky, 2023). More recently, Anguiano-Arteaga et al. (2021, 2023) independently retrieved a dominant chromophore agent in the GRS (Figure 1) via radiative transfer modelling of long-term HST/WFC3 observations (225–900 nm), which showed reasonable spectral agreement with the Carlson candidate. The retrieved chromophore particle sizes and column densities were found to be broadly consistent with those reported in earlier GRS studies (e.g., Baines et al., 2019; Braude et al., 2020).

Here, we present results from microphysical modelling of the GRS upper atmosphere (pressures < 1 bar), applying constraints on chromophore mass and particle size derived by Anguiano-Arteaga et al. (2021, 2023). Our simulations, based on the model by Toon et al. (1988), explore the vertical evolution of particle size and distribution (see Figure 2) due to sedimentation, eddy diffusion, and coagulation - following a methodology similar to that of Toledo et al. (2019, 2020) for Uranus and Neptune. These results allow us to constrain the chromophore mass production rates required to maintain a stable, long-lived chromophore layer at the expected levels. This study provides new insights into the origin and persistence of the GRS red colouration.

Figure 1. Illustrative layout of the cloud and haze structure within the Great Red Spot, as retrieved by Anguiano-Arteaga et al. (2023)

Figure 2. Simulated evolution of particle size and vertical distribution in the upper atmosphere of the Great Red Spot, as calculated using the microphysical model described in Toon et al. (1988).

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