¹Juulia-Gabrielle Moreau,¹Argo Jõeleht,¹Jaan Aruväli,²Mikko J. Heikkilä,³Aleksandra N. Stojic,²Thomas Thomberg,¹Jüri Plado,⁴Satu Hietala
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13782]
¹Department of Geology, Institute of Ecology and Earth Science, University of Tartu, Ravila 14A, Tartu, 50411 Estonia
²Department of Chemistry, University of Helsinki, P.O. Box 55 (A.I. Virtasen aukio 1), FI-00014 Finland
³Institut für Planetologie, Westfälische Wilhelms Universität Münster, Wilhelm-Klemm-Str. 10, Münster, 48149 Germany
⁴Geological Survey of Finland, Neulamäentie 5, Kuopio, FI-70211 Finland
Published by arrangement with John Wiley & Sons

Stoichiometric troilite (FeS) is a common phase in differentiated and undifferentiated meteorites. It is the endmember of the iron sulfide system. Troilite is important for investigating shock metamorphism in meteorites and studying spectral properties and space weathering of planetary bodies. Thus, obtaining coarse-grained meteoritic troilite in quantities is beneficial for these fields. The previous synthesis of troilite was achieved by pyrite or pyrrhotite heating treatments or chemical syntheses. However, most of these works lacked a visual characterization of the step by step process and the final product, the production of large quantities, and they were not readily advertised to planetary scientists or the meteoritical research community. Here, we illustrate a two-step heat treatment of pyrite to synthesize troilite. Pyrite powder was decomposed to pyrrhotite at 1023–1073 K for 4–6 h in Ar; the run product was then retrieved and reheated for 1 h at 1498–1598 K in N2 (gas). The minerals were analyzed with a scanning electron microscope, X-ray diffraction (XRD) at room temperature, and in situ high-temperature XRD. The primary observation of synthesis from pyrrhotite to troilite is the shift of a major diffraction peak from ~43.2°2θ to ~43.8°2θ. Troilite spectra matched an XRD analysis of natural meteoritic troilite. Slight contamination of Fe was observed during cooling to troilite, and alumina crucibles locally reacted with troilite. The habitus and size of troilite crystals allowed us to store it as large grains rather than powder; 27 g of pyrite yielded 17 g of stochiometric troilite.

¹William S.Cassata,²Kevin J.Zahnle,^1,3Kyle M.Samperton,¹Peter C.Stephenson,¹Josh Wimpenny
Earth and Planetary Science Letters 580, 117349 Link to Article [https://doi.org/10.1016/j.epsl.2021.117349]
¹Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, L-235, Livermore, CA 94550, USA
²Space Science Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA
³Trace Nuclear Measurement Technology Group, Savannah River National Laboratory, Aiken, SC 29808, USA
Copyright Elsevier

Trapped, paleoatmospheric xenon (Xe) in the Martian regolith breccia NWA 11220 is mass-dependently fractionated relative to solar Xe by 16.2 ± 2.7‰/amu. These data indicate that fractionation of atmospheric Xe persisted for hundreds of millions of years after planetary formation. Such a protracted duration of atmospheric Xe mass fractionation, which is particularly striking when compared to the non-fractionated state of Martian atmospheric krypton (Kr), cannot be easily reconciled with Xe escape as a neutral atom in a neutral hydrodynamic hydrogen wind. However, Xe escape as an ion coupled to a partially ionized hydrogen or oxygen wind provides a simple solution to problems associated with the neutral escape hypothesis. Ionic Xe escape requires a sufficiently high escape flux of a carrier ion (H+ or O+) and probably requires a structured planetary magnetic field to channel the flow. The end of Xe escape from Mars could be attributed to waning hydrogen sources from volcanic outgassing or from interactions of reduced impactors with surface water and ice. Alternatively, if Xe ions were driven off by O+, the end of Xe escape could be attributed to the decay of solar extreme ultra-violet radiation.