The chemical impossibility of some previous retrievals
Kevin and Jim just submitted a paper to the Astrophysical Journal, which presented a novel analytical solution for systems in chemical equilibrium that include carbon dioxide, carbon monoxide, water, methane and acetylene. They used this solution, alongside analytical solutions of temperature-pressure profiles, to show that carbon dioxide is almost always the minor species compared to carbon monoxide and water. They further explored how atmospheric mixing (it does not) and metallicity (requires temperatures hotter than 1000 K and extreme enhancements) affect this conclusion. This implies that previously reported retrievals by Madhusudhan et al. (2011) and Line et al. (2014) are chemically impossible.