Trace-element analysis of mineral grains in Ryugu rock fragment sections by synchrotron-based confocal X-ray fluorescence

A fundamental parameter-based quantification scheme for confocal XRF was applied to sub-micron synchrotron radiation X-ray fluorescence (SR-XRF) data obtained at the beamline P06 of the Deutsches Elektronen-Synchrotron (DESY, Hamburg, Germany) from two sections C0033-01 and C0033-04 that were wet cut from rock fragment C0033 collected from Cb-type asteroid (162173) Ryugu by JAXA's Hayabusa2 mission. Trace-element quantifications show that C0033 bulk matrix is Cl-like, whereas individual mineral grains (i.e., magnetite, pyrrhotite, dolomite, apatite and breunnerite) show, depending on the respective phase, minor to strong deviations. The non-destructive nature of SR-XRF coupled with a new PyMca (a Python toolkit for XRF data analysis)-based quantification approach, performed in parallel with the synchrotron experiments, proves to be an attractive tool for the initial analysis of samples from return missions, such as Hayabusa2 and OSIRIS-REx, the latter returning material from a B-type asteroid (101955) Bennu in 2023.

Automated summary

In this study, a fundamental parameter-based quantification scheme for confocal XRF was used to analyze sub-micron synchrotron radiation X-ray fluorescence (SR-XRF) data obtained from rock fragments collected from the Cb-type asteroid Ryugu. The results showed that the bulk matrix of the rock sample is similar to chlorine, while individual mineral grains exhibited varying deviations depending on their respective phases. The non-destructive nature of SR-XRF and the new PyMca-based quantification approach proved to be important tools for the initial analysis of samples from return missions.