The physical chemical and mineralogical characterisation of meteorites is of paramount importance in the study of the formation of the Solar System. This study, published in JAAS, aimed to develop a new analytical protocol to investigate the elemental and mineralogical composition of meteorites, using a combination of surface and bulk techniques, including neutrons and muons.
This work enabled the researchers to establish a methodology to distinguish a meteorite from a “meteor-wrong", classify and characterise it non-destructively. The first stage for the research group to classify a sample as a meteorite was the detection of cosmogenic radionuclides, such as 26Al, by means of g-ray spectroscopy performed at Laboratori Nazionali del Gran Sasso (LNGS, Italy).
Once the group had confirmed this, they could use neutron and muon techniques to study the composition of the bulk of the sample. In parallel, lab-based techniques such as optical microscopy investigation, micro-Raman spectroscopy and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM/EDS) have been applied in a complementary way. This innovative combination looks at the elemental and mineralogical phase composition, with particular attention to the crystallinity state of the phases.
The crystalline phases were characterised using neutron diffraction on INES, and the combined results of diffraction on the bulk micro-Raman and SEM-EDS on a thin section provided a full mineralogical description of the meteorite. The main mineral phases identified were forsterite, enstatite, and magnetite. Furthermore, troilite and kamacite (Fe–Ni alloy with Fe : Ni ratio around 95 : 5, originating from Ni substitutions) have also been found.
Using neutron resonance capture analysis (NRCA) and neutron resonance transmission imaging (NRTI) on INES, the researchers were able to determine some of the elements present in the meteorite (Fe, Mn, Co), and its homogeneity on a millimetre scale. Thanks to muonic atom X-ray emission spectroscopy (μXES) at the RIKEN facility at ISIS, they could quantify the weight ratio of the main elements in the sample (O, Si, Mg, Fe).
This study proves that it is possible to identify a sample as being a meteorite and characterise the bulk of it non-destructively and is going to be applied for studying other meteorites belonging to museum collections, opening up a way to investigate new ones that will arrive to Earth from space in the future.
Further information
The full paper can be found at DOI 10.1039/d2ja00263a, and the study also featured on the back cover of the journal issue.
