THE EARTHS MISSING XENON: A COMBINATION OF EARLY DEGASSING AND OF RARE GAS LOSS FROM THE ATMOSPHERE

Abstract

The under-abundance of Xe in the Earth's atmosphere relative to solar system abundances has been long recognised and is usually referred to as the “missing xenon problem”. It is suggested here that this feature of the Earth's composition is the result of processes operative during its accretion and earliest degassing history. In essence, it arises from several competing processes. One of these is sorption of rare gases onto the accreting material, which favours an excess of Xe relative to lighter rare gases. Another is the subsequent fractional degassing of melts formed during or shortly after accretion, which favours preferential degassing of Xe over lighter rare gases from the Earth's interior. These two processes are combined with a major loss of rare gas from the Earth's early atmosphere, possibly accompanying hydrogen hydrodynamic escape.