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Extended Analysis of a Potential Jovian Chromophore

Presentation #505.02 in the session Origin and Evolution of Giant Planet Systems I (Oral Presentation)

Published onOct 23, 2023
Extended Analysis of a Potential Jovian Chromophore

Identifying the coloring agent, or chromophore, that causes the reddish hues in Jupiter’s atmosphere has been an area of active study for several decades (e.g., Simon et al. 2015, J. Geophys. Res. 120, 483-494). In 2016, Carlson et al. (2016, Icarus 274, 106-115) published the results of a laboratory experiment meant to develop a new potential Jovian chromophore formed by UV photolysis of ammonia and acetylene gas mixtures. In that work, the authors measured the transmission spectra of the deposited thin films at various time intervals, ranging from 0 to 328 hours; due to the absence of significant interference fringes in the 70-hour exposure transmission spectrum, it was used to derive the optical properties of this potential chromophore using a real index of refraction of 1.4 and a film thickness of 0.7 microns. Here, we present Carlson’s effort to eliminate some incorrect assumptions in the previous work by (1) deriving the changing thickness of the sample as a function of time and (2) solving for the wavelength dependence of the sample’s real index of refraction. As a result, he produced a series of complex indices of refraction of the chromophore sample as a function of irradiation exposure time. He found that the imaginary index of the sample increased with UV exposure time and that the blue slope steepened, which is consistent with the results of similar experiments (e.g., Faure et al. 2021, Icarus 364). The final optical constants can provide new invariable inputs to models of Jupiter’s clouds at wavelengths sensitive to the color of the chromophore, thereby decreasing the amount of degeneracy that normally plagues that wavelength regime. We also provide an example of the application of these data to optical spectra of Jupiter’s atmosphere.

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