Opsmeltning og Impact mixing af tidlige asteroider.

Large-scale melting of asteroids and planetesimals is now known to have taken place ex-tremely early in solar system history [1]. The first-generation bodies produced by this process would have been subject to rapid collisional reprocessing, leading in most cases to fragmentation and/or accretion into larger-sized bodies [2]. Achondritic meteorites provide a unique source of information about the nature of these early events. However, the fragmentary character of this record makes it difficult to interpret. High-precision oxygen isotope analysis has proved to be an important technique in understanding the relationship between the different groups of achondrites [3, 4]. Here we present new oxygen isotope evidence con-cerning the role of large-scale melting and subsequent impact mixing in the evolution of three important achondrite groups: the main-group pallasites, meso-siderites and HEDs.