The origin of meteorites and the constrained equilibrium condensation theory

Abstract Microscopic examination and microprobe analyses were made in individual chondrules in unequilibrated meteorites. Our observations as well as published data are compared with the predictions and consequences of the “constrained equilibrium” theory of Blander and Katz. The large variety of textures of chondrules is shown to be consistent with the postulate that chondrules were formed as subcooled liquid drops. The distribution and concentrations of oxidized and metallic iron in equilibrated and unequilibrated chondrites are consistent with constraints imposed by nucleation kinetics and the consequent supersaturation of iron vapor during the condensation process. The different contents of volatile elements of different chondrites fits the theory in a simple manner consistent with the calculations of Larimer and Anders by taking into account the relative rates of accretion and rates of cooling of the gas which governed the condensation and incorporation of elements of different volatility. Most of the compositional and textural features in chondrites thus could have been formed during the condensation and accretion processes in a cooling nebula.