The element phosphorus (P) is central to ecosystem growth and is proposed to be a limiting nutrient for life. The Archean ocean may have been strongly phosphorus-limited due to the selective binding of phosphate to iron oxyhydroxide. Here we report a new route to solubilizing phosphorus in the ancient oceans: reduction of phosphate to phosphite by iron(II) at low (<200 °C) diagenetic temperatures. Reduction of phosphate to phosphite was likely widespread in the Archean, as the reaction occurs rapidly and is demonstrated from thermochemical modeling, experimental analogs, and detection of phosphite in early Archean rocks. We further demonstrate that the higher solubility of phosphite compared to phosphate results in the liberation of phosphorus from ferruginous sediments. This phosphite is relatively stable after its formation, allowing its accumulation in the early oceans. As such, phosphorus, not as phosphate but as phosphite, could have been a major nutrient in early pre-oxygenated oceans.

aWe present a study of the reactions of the meteoritic mineral schreibersite (Fe,Ni) 3 P, focusing primarily on surface chemistry and prebiotic phosphorylation. In this work, a synthetic analogue of the mineral was synthesized by mixing stoichiometric proportions of elemental iron, nickel and phosphorus and heating in a tube furnace at 820 1C for approximately 235 hours under argon or under vacuum, a modification of the method of Skála and Drábek (2002). Once synthesized, the schreibersite was characterized to confirm the identity of the product as well as to elucidate the oxidation processes affecting the surface. In addition to characterization of the solid product, this schreibersite was reacted with water or with organic solutes in a choline chloride-urea deep eutectic mixture, to constrain potential prebiotic products. Major inorganic solutes produced by reaction of water include orthophosphate, phosphite, pyrophosphate and hypophosphate consistent with prior work on Fe 3 P corrosion. Additionally, schreibersite corrodes in water and dries down to form a deep eutectic solution, generating phosphorylated products, in this case phosphocholine, using this synthesized schreibersite.

Carbonyl and nitrogen complexes with Rh are produced in a molecular beam using laser ablation and a pulsed-nozzle source. Mass-selected ions of the form Rh(CO) and Rh(N) are investigated via infrared laser photodissociation spectroscopy. The fragmentation patterns and infrared spectra provide information on the coordination and geometries of these complexes. The shifts in vibrational frequencies relative to the uncoordinated ligands give insight into the nature of the bonding interactions involved. Experimental band positions and intensities are compared to those predicted by density functional theory (DFT). Rh coordinates only four nitrogen molecules, whereas it can accommodate five carbonyl ligands. The fifth CO ligand resides in an axial site with bonding intermediate between coordination and solvation. The carbonyl stretch in Rh(CO) (2160 cm) is blue-shifted with respect to the molecular CO vibration (2143 cm). Conversely, the N-N stretch in Rh(N) (2297 cm) is red-shifted with respect to the free N vibration (2330 cm). The opposite directions of these frequency shifts is explained by a combination of σ donation and electrostatic ligand polarization.

The surface of an analogue to the meteoritic mineral schreibersite or (Fe,Ni) 3 P was investigated to provide insight into the interaction of the mineral surface with prebiotic molecules such as water, methanol, and formic acid. A protocol for creating synthetic metal-phosphide samples with a surface reflectivity suitable for reflection−absorption infrared spectroscopy (RAIRS) was developed and is outlined in this paper. Scanning electron microscopy coupled with energy dispersive spectroscopy revealed an average defect size less than 1 μm and evidence of subsurface phosphorus segregation. At surface temperatures between 120 and 140 K, RAIRS spectra indicate that water and formic acid interact molecularly with surface atoms, while methanol appears to dissociate into methoxy and protons upon adsorption. The observed infrared spectra provide insight into the adsorption geometries of these prebiotic molecules on synthetic schreibersite. This data suggests the importance of the schreibersite mineral surface in aqueous-phase schreibersite-mediated phosphorylation experiments that have been performed by others and strengthens the argument that schreibersite-induced chemistry could occur in astrochemical environments.

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The detection of ammonium-bearing compounds in meteorites, comets, and in Earth’s geologic record is challenging due to the volatilization of ammonia during heating. Struvite (MgNH4PO4·6H2O) is an ammonium-bearing phosphate mineral considered to be relevant to the origin of organophosphates on the early Earth, and it is possible that this mineral may have formed on the early Earth and in meteorites in favorable environments. However, in contrast to other phosphate minerals such as those within the apatite mineral group, there is little evidence of struvite on the early Earth and no detection of it in meteorites, where such high-N (nitrogen) and low-H2O conditions may be more commonplace. Here, we demonstrate that struvite quickly loses ammonia and transforms into a new suite of minerals; hence, this mineral is ephemeral. This ephemerality is demonstrated by the thermal decomposition reactions of struvite that lead to the mineral newberyite (MgHPO4·3H2O), an acidic phosphate mineral. Both struvite and newberyite transform into magnesium pyrophosphate and magnesium triphosphate, which are the final products of thermal decomposition (T > 200 °C). However, magnesium pyrophosphate itself reacts with calcium-bearing minerals such as calcite or gypsum and transforms into orthophosphate minerals and polyphosphate salts. Such reactions could have occurred in meteorites as well as on the early Earth. The present research helps identify how ephemeralbut prebiotically relevantminerals may be lost from the geologic record, but still could have played a role in the development of life.

Abstract Planetary habitability is in part governed by nutrient availability, including the availability of the element phosphorus. The nutrient phosphorus plays roles in various necessary biochemical functions, and its biogeochemical cycling has been proposed to be extremely slow due to a strong coupling to the rock cycle via mineral weathering. Here we show a route to P liberation from water-rock reactions that are thought to be common throughout the Solar System. We report the speciation of phosphorus in serpentinite rocks to include the ion phosphite (HPO32- with P3+) and show that reduction of phosphate to phosphite is predicted from thermodynamic models of serpentinization. As a result, as olivine in ultramafic rocks alters to serpentine minerals, phosphorus as soluble phosphite should be released under low redox conditions, liberating this key nutrient for life. Thus, this element may be accessible to developing life where water is in direct contact with ultramafic rock, providing a source of this nutrient to potentially habitable worlds.

Abstract. We have developed a multimodal ion source design that can be configured on the fly for various analysis modes, designed for more efficient and reproducible sampling at the mass spectrometer atmospheric pressure (AP) interface in a number of different applications. This vacuum-assisted plasma ionization (VaPI) source features interchangeable transmission mode and laser ablation sampling geometries. Operating in both AC and DC power regimes with similar results, the ion source was optimized for parameters including helium flow rate and gas temperature using transmission mode to analyze volatile standards and drug tablets. Using laser ablation, matrix effects were studied, and the source was used to monitor the products of model prebiotic synthetic reactions.