The Investigation of Geologically Relevant Metal Phosphites as a Plausible Source of Phosphorus in Prebiotic Chemistry

To understand the origin of life, the abiotic incorporation of phosphorus in energy-promoting molecules like adenosine triphosphate (ATP) need to be identified. However, a consensus has not been reached on the source of phosphorus for prebiotic chemistry on Archaean Earth. One hypothesis is that metal phosphites were an important source of phosphorus for prebiotic chemistry. The primary issue with this hypothesis is the lack of phosphites in the geological rock record, where different phosphorus compounds (mostly inorganic phosphates) are observed instead. Two geologically relevant metal phosphites with varying waters of hydration, CaHPO3 and MgHPO3, were synthesized, structurally characterized, and thermally processed to determine if the conditions on early Earth could explain the lack of phosphite in the geological record. The phosphites were characterized using Thermogravimetic Analysis, X-Ray Diffraction, and phosphorus Nuclear Magnetic Resonance. From these experiments, interstitial waters associated with the metal phosphites are dehydrated from the compounds, which influences their reactivity. From Thermogravimetric Analysis, and phosphorus Nuclear Magentic Resonance data, simultaneous polymerization and oxidation is observed defining reactivity. Also, X-Ray Diffraction data validated the synthesis of metal phosphites in the lab. Since they are subject to polymerize and oxidize at higher temperatures in different environments, metal phopshites may not easily preserved in the geological rock record. Preliminary data to support this investigation will be presented here

Identifying the Mineral Source of Phosphorus-Containing Molecules in Space

Only a few phosphorus-containing molecules have been identified in extraterrestrial environments, but the mineral source of these gas-phase molecules has yet to be identified. The objective of this project is to identify the conditions that cause small phosphorus-containing molecules to desorb from the surface of schreibersite, an iron-nickel phosphide mineral. To determine these conditions, we place a sample of schreibersite in an ultrahigh vacuum (UHV, with a pressure of less than 1 x 10-9 torr) chamber and measure its ability to react with small molecules (e.g., H2O, CH4, andCO2) using reflection-absorption infrared spectroscopy (RAIRS). While preparing to run these experiments, we encountered and troubleshot many issues that arose. One problem we ran into was the pressure not being low enough in the UHV chamber. We leak tested using a quadrupole mass spectrometer (QMS), found no leaks that were larger than 2 x 10-9 torr, but observed many peaks corresponding to hydrocarbons. To correct this, we disassembled the chamber, cleaning the interior with acetone, isopropanol, and then methanol. We also checked for metal shavings, loose pieces of fiberglass from the covering of our wires, and any other debris. Once everything was put back together, the pressure remained low enough to continue. Another issue we came across was the cooling of the sample. These experiments require temperatures of at least -173℃. This is crucial for small molecules to be able to stick to the surface of the schreibersite sample and to effectively model extraterrestrial environments like cometary coma and dense molecular clouds in the interstellar medium. To lower the temperature, we attached a cryogenic cooling system to the sample holder. The lowest temperature we’ve reached so far is -190.15℃ (83 K). Updates on sample imaging, RAIRS alignment, and preliminary data will also be presented

Evolution of Ephemeral Phosphate Minerals on Planetary Environments

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 \u3e 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

The Evolution of the Surface of the Mineral Schreibersite in Prebiotic Chemistry

We present a study of the reactions of the meteoritic mineral schreibersite (Fe,Ni)3P, 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 °C 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 Fe3P 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

Multimodal Vacuum-Assisted Plasma Ion (VaPI) Source with Transmission Mode and Laser Ablation Sampling Capabilities

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

Serpentinization as a Route to Liberating Phosphorus on Habitable Worlds

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

Serpentinization as a Route to Liberating Phosphorus on Habitable Worlds

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

Archean Phosphorus Liberation Induced by IRON Redox Geochemistry

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 (°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

Plant size, latitude, and phylogeny explain within-population variability in herbivory

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth