Studies of water on Earth and in the asteroid belt

It is increasingly accepted that the fast diffusion of water in glass renders measurements of melt inclusions suspect except in very small tephra. Therefore there is much interest in the use of water measurements in nominally anhydrous minerals such as clinopyroxene and application of a partition coefficient as an alternative means to estimate magmatic water contents. Having experimentally determined appropriate partition coefficients we have calibrated water measurements on the SHRIMP SI against both FTIR and Cameca 6f measurements on independently analysed minerals. A detailed study of clinopyroxenes from the Azores islands demonstrates the potential of this mineral to provide accurate estimates of magmatic water contents and shows that the Azores islands reflect mantle wet-spots within an overall damp area of the upper mantle. Analyses of clinopyroxene from sub-arc mantle xenoliths shows that the arc lithosphere retains significant amounts of water in addition to an arc trace element signature. Clinopyroxene from continental flood basalts suggest that these lavas have similar water contents to arc lavas and could be derived from ancient sub-arc lithospheric domains. 
It has often been postulated that Earth’s water was at least in part, derived from carbonaceous chondrite meteorites, many of which contain abundant evidence for aqueous alteration. However, the age of this alteration is not well constrained and one recent model suggests that their parent bodies are frozen mud balls. A suite of carbonaceous chondrites has been analysed for U-series isotopes revealing extensive disequilibria that could be explained by fluid movement within the last 1 Myr or less. This could have been triggered by the impacts that broke these meteorites off their parent bodies.