Five-stage multielement separation procedure: A unique and essential tool for the multi-isotopic analyses of precious (< 30 mg) extraterrestrial materials

Abstract

The latest and ongoing sample return missions from extraterrestrial objects present an opportunity to expand our knowledge of the chemical composition and subsequent evolution of the Solar System, beyond the information that can be obtained from the study of meteorites. Nevertheless, a potential limitation of such missions, at least in the foreseeable future, would be the recovery of a limited amount of sample. In light of these considerations, we have developed a multi-element chemical separation protocol utilizing a sample amount of approximately 25 mg. With this sample amount (and less), we can successfully separate elements including Mg, K, Ca, Ti, Cr, Fe, Ni, Zn, Sr, Zr, Mo, Ba, REEs, Hf, W, Pb, and U. This includes the crucial elements Ti and Cr, whose isotopic compositions are used for the latest classification of meteorites, and in turn the parent asteroidal materials. The new method achieved chemical yields for these elements after separation of greater than 90% for both major and trace elements in the Murchison meteorite (with an exception for Pb with 85%). The corresponding total procedural blanks were negligible, representing less than 0.1% for the majority of the elements. This method was specifically designed for the analysis of small samples (< 30 mg) of extraterrestrial materials from sample return missions, such as Hayabusa2 and OSIRIS-REx. It will be of significant application in future missions such as MMX and Artemis where limited quantities of asteroidal, cometary, planetary, and other primitive Solar System solids will be returned.