Published online by Cambridge University Press: 12 April 2016
On the basis of 180/160 and 170/160 ratios, meteorites and planets can be grouped into at least nine categories, as follows (in order of increasing 1°0): (1) type L and LL ordinary chondrites; (2) type H ordinary chondrites, type HE irons, and CI carbonaceous chondrites; (3) the nakhlites and Shergotty; (4) the earth, moon, and enstatite chondrites and achondrites; (5) basaltic achondrites, hypersthene achondrites, mesosiderites, pallasites and type IRB irons; (6) the ureilites; (7) C2 carbonaceous chondrite matrix, Bencubbin, Weatherford, and Kakangari; (8) C3 carbonaceous chondrites; (9) pallasites Eagle Station and Itzawisis. Objects of one category cannot be derived by fractionation or differentiation from the source materials of any other category, but must represent samples of different regions of an i nhomogeneous solar nebula. The isotopic classification, together with major-element abundances, provides a powerful method for recognition of interrelationships of the various meteorites and their parent bodies.