Planetary noble gas abundance patterns

The lower terrestrial Xe/Kr ratio has since usually been considered a feature of the Earth (see, however, Ozima and Podosek 1999 and Rayleigh distillation section below). Although relative abundances in chondrites were historically called the planetary pattern based on similarities with the Earth s atmosphere, and this in turn drove the search for the missing Xe , it is now clear that these trapped meteoritic gases do not have such direct relevance to the planets, and so are no longer properly termed planetary . However, the reason why the Earth does not exhibit a systematic depletion pattern relative to solar gases (Fig. 2) still requires explanation. 

The pattern exhibited by Mars closely follows that of the Earth, with a near-solar Xe/Kr ratio. The available data for Venus likewise suggest solar-like Xe/Kr, although uncertainties are large. Despite these uncertanties, however, it seems clear that Venus differs markedly from the other two terrestrial planets in having an Ar/Kr ratio that is also close to solar. 

Rayleigh distillation and planetary noble gases. It has been suggested that the abundance pattern of trapped Q-phase noble gases— the most abundant and widely distributed primordial component in meteorites (Wider 1994 Busemann et al. 2000  

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