Hybrid X-ray Diffraction for Planetary Mineralogical Analysis of Unprepared Samples

A new type of X-ray diffraction (XRD) planetary instrument is being developed based on an innovative hybrid concept that allows performing both powder and single-crystal XRD measurements, mak-ing it possible to analyze minerals with limited or no sample preparation. Powder XRD (pXRD), the tech-nique used by the CheMin instrument of MSL [1], will be used when fine-grained samples are presented to the instrument, either in their native state or after prepara-tion with a grinding tool. Single-crystal XRD (sXRD) using polychromatic radiation (Laue diffraction) will be applied when samples are too coarse for pXRD. Laue analysis will allow identification of minerals in unprepared samples and enable ab-initio determination of crystalline phases unknown to current crystallo-graphic databases. In parallel to either diffraction analysis, the instrument will provide X-ray fluores-cence (XRF) data for chemical analysis of the sample. A possible implementation of the instrument concept is presented in Figure 1 in the form of a contact instru-ment fitted to the robotic arm of a rover. Alterna-tively, the instrument could be installed inside a rover/lander for analysis of delivered unprepared sam-ples.