Nature Astronomy, Published online: 24 August 2023; doi:10.1038/s41550-023-02047-0

The visible–near-infrared spectrum of the dark spot that appeared on Neptune in 2018 indicates the presence of material that makes the aerosol layer at 5 bar darker at visible wavelengths. Such material can come from deeper layers via upwelling or by sublimation of H2S ice that reveals the darker condensation nuclei.

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