Hydration of initially anhydrous silicates and oxides is a common and significant early solar system processes recorded by the carbonaceous chondrites We present new data constraining the hydrogen isotope geochemistry of the CM chondrites, which are characterised by a wide range in degree
of hydration. Our study makes use of a recently developed method for analysis of D/H ratios of 10^(-9) mol quantities of water released by heating small (10's of microgram) solid samples
