Extended Data Fig. 1: Steady-state mean mixing ratios for PH₃ (left) and GeH₄ (right) as a function of water enrichment at different pressure levels in our simulations.

The squares represent mean values while the triangles represent final states. The vertical bars signify the 1σ standard deviations, and the gray dashed lines demarcate the minimum observed values with their uncertainty ranges given by the arrows^7,9. There is a distinct trend to lower mixing ratios as a function of increasing water enrichment, highlighting the overall effect of increased convective inhibition near the LCL. As the mean mixing ratios at ~ 4.5 bars (purple) are unable to match the observed values, particularly for ≥7.5 × solar oxygen enrichment, this suggests an upper bound for the Jovian water content. For the lower water enrichment cases, the mean mixing ratios across various pressure levels exhibit very close values, which is particularly true for GeH₄. As such, PH₃ and GeH₄ lose their sensitivity to the water enrichment if Jupiter hosts too little water in its deep atmosphere. Coupled with the requirement from CO for at least an enrichment of 2.5 × being necessary to match observations, this limits the deep water content to a supersolar oxygen enrichment between 2.5-5.0.