Abstract Previous analysis of Neptune’s atmosphere using near-infrared Gemini/NIFS observations found the strongest spectral signature of hydrogen sulphide (H2S) to be at the planet’s south pole. Conversely, analysis of microwave observations with ALMA in 2019 suggested a distribution of H2S that peaks in the midlatitudes and is strongly depleted towards the pole. We analyse near-infrared observations from VLT-SINFONI in 2018 and fit a parametrized cloud model to the data using nested sampling. By prescribing a latitudinally-varying methane (CH4) profile previously derived from visible light observations, we find general agreement with the microwave analysis, with an enhancement of H2S by a factor of ∼4 at the southern midlatitudes compared to polar latitudes. The stronger spectral signature at the pole is explained with a deeper cloud top, resulting in a higher cloud-top H2S column abundance in this region. Our results are indicative of deep upwelling at the midlatitudes, with downwelling at the pole and possibly near the equator.
penn et al. (Mon,) studied this question.