Research Division Seminar
Solar system elemental abundances: The importance of CI chondrites

Solar system elemental and isotopic abundances are widely used as a reference composition in astronomy, planetary sciences, and cosmochemistry. Since the earliest developments about a century ago the quest for quantitative solar system abundances evolved rapidly in two disciplines:

Stellar spectroscopy and meteoritics. The solar system abundances are ideally derived from the solar photospheric spectrum and appropriate solar atmospheric modelling, but a full and well-determined set of abundances of all 83 stable and long-lived elements currently is still not possible. Therefore meteorites, and recently, returned samples from asteroids Ryugu and Bennu, will continue to serve as additional proxies for the solar system composition because all elements can be accurately quantified in them. The talk gives a historical perspective on how and why the small class of CI chondrites (five known falls among about 1100 recorded meteorite falls) was selected as solar abundance proxy, and describes some of the common challenges of these mineralogically highly complex meteoritic and returned samples which, however, seemed to have retained the primitive elemental composition for elements for refractory than water ice.