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Mesonian

Temperate giant planets

Mesonian (Harriot)
Image from AstroChara
Harriot, a mesonian gas giant
In NoLWoCS, Mesonians (prefix: Meso-; eg. MesoNeptunian, MesoJovian) are temperate giant planets, with tropopause temperatures between 200 K, below which ammonium hydrosulfide and ammonia clouds dominate and the planet becomes a Psychronian, and 350 K, above which water clouds dissipate and the planet becomes a Zestonian. Mesonians are characterized by the presence of clouds of water (H2O), which gives them a white colour. On Mesonians receiving sufficient high energy radiation, photochemical haze forms, producing a beige tint much like on Psychronians.

Colour variations on Mesonians are broadly similar to Psychronians, often featuring numerous bands and storms with varying colours, as well as bluer regions arising from cooler temperatures or storms, although the former may also result in formation of high altitude ammonium hydrosulfide clouds in some cases.

Mesonians can be found in a wide range of masses, from neptunians to superjovians. Owing to their common formation location near the water frost line coinciding with a distance suitable for this temperature type, as well as their internal heat flux, most jovian planets are either Mesonians or Psychronians.
 
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Development Notes
Text by AstroChara
John M. Dollan, with comments by Steve Bowers
Initially published on 31 December 2007.

Overhauled 2025-10-14 by AstroChara
 
 
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