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.