Work

Reconciling near-infrared and microwave analyses of Neptune’s hydrogen sulphide distribution

Year: 2026

Type: article

Abstract: ABSTRACT Previous analysis of Neptune’s atmosphere using near-infrared Gemini/NIFS observations found the strongest spectral signature of hydrogen sulphide (H$_2$S) to be at the planet’s south pole. Conversely, analysis of microwave observations with the Atacama Large Millimeter/submillimeter Array in 2019 suggested a distribution of H$_2$S that peaks in the mid-latitudes 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 (CH$_4$) profile previously derived from visible light observations, we find general agreement with the microwave analysis, with an enhancement of H$_2$S by a factor of $\sim$4 at the southern mid-latitudes compared to polar latitudes. The stronger spectral signature at the pole is explained with a deeper cloud top, resulting in a higher cloud-top H$_2$S column abundance in this region. Our results are indicative of deep upwelling at the mid-latitudes, with downwelling at the pole and possibly near the equator.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag688

Authors: Joseph Penn, Patrick G J Irwin, Jack Dobinson, Leigh N Fletcher, Nicholas A Teanby, Michael T Roman

Institutions: University of Oxford, University of Leicester, University of Bristol, Adolfo Ibáñez University

Language: English

Topic: Astro and Planetary Science

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

SDG: Climate action

Open Access status: gold

Estimated APC paid: $3,046