Chemistry induced by the impacts: Observations

Summary

This paper reviews spectroscopic measurements relevant to the chemical modifications of Jupiter's atmosphere induced by the Shoemaker-Levy 9 impacts. Such observations have been successful at all wavelength ranges from the UV to the centimeter. At the date this paper is written, newly detected or enhanced molecular species resulting from the impacts include H₂O, CO, S₂, CS₂, CS, OCS, NH₃, HCN and C₂H₄. There is also a tentative detection of enhanced PH₃ and a controversial detection of H₂S. All new and enhanced species were detected in Jupiter's stratosphere. With the exception of NH₃ (and perhaps H₂S and PH₃), apparently present down to the 10–50 mbar level, the minor species are seen at pressures lower than 1 mbar or less, consistent with a formation during the plume splashback at 1–100 microbar. NH₃ may result from upwelling associated with vertical mixing generated by the impacts. The main oxygen species is apparently CO, with a total mass of a few 10¹⁴ g for the largest impacts, consistent with that available in 400–700 m radius fragments. The observed O/S ratio is reasonably consistent with cometary abundances, but the O/N ratio (inferred from CO/HCN) is much larger, suggesting that another N species was formed but remained undetected, presumably N₂. The time evolution of NH₃, S₂, CS₂ shows evidence for photochemical activity taking place during and after the impact week.