Accretion Dynamics and Timescales: Relation to Chondrites

摘要: In this chapter we consider aspects of the formation a presumed initial population approximately kilometer-sized planetesimals and their accretion to form larger bodies in asteroid belt, including parent meteorites. Emphasis is on timescales predicted from dynamical models comparison with measured ages meteoritic components. simplest models, for planetesimal protoplanetary embryos are not consistent apparent age difference between CAIs chondrules, inferred duration chondrule formation, or expected degree heating metamorphism due 26Al. We suggest alternative scenarios that may delay and/or produce chondrites recycled debris first-generation were collisionally disrupted after Jupiter formed. discuss collisional evolution during accretion, consequences lithification The region solar nebula corresponded belt originally contained ~103× its present mass solid matter. does represent an unbiased sample material. Meteorites preferentially derived few tens hundreds kilometers size; these sufficiently small numerous leave remnant depletion but large enough survive subsequent 4.5 G.y. evolution.