The spectrum of Jupiter's Great Red Spot: The case for ammonium hydrosulfide (NH4SH)

Here we present new ultraviolet-visible spectra of irradiated ammonium hydrosulfide (NH₄SH), a reported jovian atmospheric cloud component, for a range of temperatures and radiation doses and make assignments to the spectral features. We show that the combination of radiolysis and thermal annealing of NH₄SH causes the originally featureless ultraviolet-visible reflectance spectrum to evolve into one that absorbs in the ultraviolet-visible region. Furthermore, we find that our laboratory spectra resemble HST spectra below 500 nm, suggesting that the more stable reaction products of NH₄SH radiolysis are likely an important component of the Great Red Spot.