Investigation of schreibersite and intrinsic oxidation products from Sikhote-Alin, Seymchan, and Odessa meteorites and Fe3P and Fe2NiP synthetic surrogates

This work presents a comprehensive investigation of schreibersite inclusions within iron-poor and iron-rich meteorites, and of the associated intrinsic low-temperature oxidation products observed after exposure to terrestrial weathering. First, a thermodynamic equilibrium modeling of the oxidation of schreibersite was carried out and showed that oxidation is mostly limited to the surface in the absence of other ions and/or water. This oxidation occurs rapidly (less than a few weeks) and is mediated by the atmosphere, forming primarily iron oxides and iron phosphates. Second, detailed analyses of meteorite schreibersite inclusions and synthetic schreibersite surrogates (Fe3P and Fe2NiP) were performed using surface characterization techniques such as micro-Raman spectroscopy, atomic force microscopy (AFM), electrostatic force microscopy (EFM), electron microprobe analysis (EPMA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Such thorough analyses are required as many prebiotic reactivity studies performed use meteoritic samples that have been somewhat exposed to Earth weathering. We find that, while the meteorite samples have not been introduced directly into water, they all bear significant oxidation signatures that appear to be similar for both short-term and long-term natural weathering corrosion processes. In addition, we find that synthetic schreibersite samples have similar surface and sub-surface chemistry and are reasonable chemical proxies for natural schreibersite. The thorough analytical studies detailed in this paper provide a chemical model for schreibersite oxidation products.