Figure 8.

Comparison of the CI chondrite-normalized estimated volatile abundances in Earth and Venus. The Venus abundances assume that its interior has entirely degassed. The relative depletions in Venus's C and ⁴⁰Ar (from decay of ⁴⁰K) suggest that this was not always the case. The large relative enrichments in Ne and ³⁶Ar indicate that Venus did not have the same mix of sources as Earth (see the text for discussion). The data for the Earth are from Marty [47], and those for Venus from Fegley [113] except for Xe which is from Bogard [114] but its value is very uncertain.