Chondrites and the Solar Nebula

摘要

For the inquisitive human mind, among the most tantalizing and inttiguing questions is that of how out solar system formed. The answer lies, at least in pan, within the asteroid belt, a zone 2 to 4 astronomical units from the sun, between the orbits of Mars and Jupiter, which contains hundred of thousands of small, rocky planetesimals. The asteroid belt is the source of an important group of meteorites, known as chondrites because they contain abundant millimeter-sized silicate spherules called chondrules (from the Greek word "khondros" meaning granule) (see figure). The chondrites formed 4.56 billion years ago within the solar nebula, a disk of collapsed dust and gas that was the birthplace of our sun and the planets (1). The chondrites have remained relatively unchanged since they formed and hence provide a record, albeit imperfect, of early solar nebular processes. One of the major challenges of mete -oriticists is to unravel this record to provide constraints on the type and duration of processes that occurred within the solar nebula. Such information is critical as input data for large-scale models of the solar nebula (2).