Chondrites are a type of stony meteorite consisting of an agglomeration of millimeter-sized globules called chondrules, and the are thought to be unchanged since the original condensation out of the nebula from which the sun and solar system formed. .... ... Connelly and Love (2 installations, US) review present ideas concerning the formation of chondrules in a process of repeated, localized, brief (minutes to hours) melting of cold aggregates of mineral dust in the protoplanetary nebula that was the precursor to the solar system. Astrophysical models of chondrule formation have been unable to explain the petrologically diverse nature of chondrites, of which there are many types. However, a nebular shock-wave model for chondrule formation is consistent with many of the observed petrological and geochemical properties of chondrules, and explains various structural properties of the particles. Identifying the source of the shock-wave heating is still a problem, but the author suggests several possibilities.

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