The absolute chronology and thermal processing of solids in the solar protoplanetary disk

Dating the First Solids The solar system's first solids: calcium-aluminum–rich inclusions and chondrules are found in meteorites and provide a direct record of the dynamics of the solar protoplanetary disk that led to the formation of the solar system. Previous results indicate that chondrules formed 1 to 2 million years after the inclusions—an age difference that has been used in constructing models of chondrule formation. Based on uranium- and lead-isotope measurements of a collection of these primitive materials, Connelly et al. (p. 651 ) show that chondrules in fact started to form at the same time as the inclusions, 4.567 billion years ago, and that their formation took about 3 million years.