Since the inception of mass spectrometry more than a century ago, the field has matured as analytical capabilities have progressed, instrument configurations multiplied, and applications proliferated. Modern systems are able to characterize volatile and nonvolatile sample materials, quantitatively measure abundances of molecular and elemental species with low limits of detection, and determine isotopic compositions with high degrees of precision and accuracy. Consequently, mass spectrometers have a rich history and promising future in planetary exploration. Here, we provide a short review on the development of mass analyzers and supporting subsystems (eg, ionization sources and detector assemblies) that have significant heritage in spaceflight applications, and we introduce a selection of emerging technologies that may enable new and/or augmented mission concepts in the coming decades.

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The influence of mass spectrometry is far‐reaching! In this issue of the Journal of Mass Spectrometry, Authors Arevalo, Ni and Danell describe the rich history and promising future applications of the mass spectrometer in the investigation of planetary bodies. Mass analyzers sent into space and deployed to planetary bodies are inherently different from the instruments used in a conventional laboratory setting. Payload instruments must be small and especially rugged, so that they survive the launch, cruise, and deployment phases of the mission. They must also provide a specific set of analytical objectives, including sensitive and quantitative measurements of chemical composition, and isotopic, elemental, and molecular abundances of both volatile and nonvolatile components. These systems must operate autonomously and provide unbiased information on planetary materials. In this month's Special Feature the authors discuss instrument types, their operational requirements, and highlight the expanding scope of mass spectrometry in interplanetary studies.

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Molybdenum (Mo) in marine sediments has been used as a paleoproxy to provide evidence for past oceanic euxinic and sulfidic conditions through its association with pyrite. Here, we examine the adsorption of Mo to the pyrite precursors mackinawite and greigite and assess the robustness of this association during iron sulfide phase transformations. Tetrathiomolybdate (MoS 4 2− ) adsorption experiments were done using mackinawite and greigite that had been characterized using powder X-ray diffraction and Raman spectroscopy. Adsorption of tetrathiomolybdate to mackinawite and to a primarily greigite mixture was similar. Both showed little change to the mineral phase upon adsorption. Relative to previously published data on pyrite, there was a much greater amount of Mo adsorption and a different mode of adsorption. A mackinawite/greigite mixture was also synthesized through an alternative method that more closely mimicked environmental conditions with a brief in situ aging to form an initial phase of iron sulfide, likely highly disordered mackinawite, and the near-immediate addition of MoS 4 2− . X-ray photoelectron spectroscopy results support the adsorption of tetrathiomolybdate and its concomitant reduction to Mo(IV). The Mo-adsorbed mackinawite/greigite mixture was transformed through heating into a greigite/pyrite mixture while monitoring Mo release to the aqueous phase. Here, the sorption of Mo on the solid phase promoted the transformation of mackinawite into pyrite upon heating without diagenetic loss of Mo to the aqueous phase. These results support the early capture of MoS 4 2− to less-stable forms of iron sulfide with negligible diagenetic loss during subsequent transformation. This work continues to point to Mo(VI) as a plausible oxidant of FeS to FeS 2 within natural euxinic settings.