Differences in emission spectra resulting from melt vaporisation into a volatile atmosphere. The black spectrum represents the PO- and CO-rich atmospheric composition showcased in Figure 1, assuming f = 1/4. The green spectrum corresponds to an identical composition, but for a dayside-confined temperature regime ( f = 2/3). The other coloured spectra illustrate the effects of melt vaporisation for each heat redistribution value, modelled using LavAtmos. Bright spectra represent a 1 bar volatile atmosphere, while faded spectra correspond to a 10 bar volatile atmosphere. The shown JWST data is the Eureka! reduction of the NIRCam and MIRI observations from Hu et al. (2024). The two photometric points are the Spitzer data from Demory et al. (2016b).