'We preserve them embedded in at least many of the rock to help make that transportation process as Secure as possible, and after that the exertions of receiving them out with the rock happens again in the lab.' ?18O=18Rsample-18Rstandard/18RstandardwhereR18=18O/16O?17O=17Rsample-17Rstandard/17RstandardwhereR17=17O/16O some time of accretion for