ACS Earth and Space Chemistry最新文献

Investigating the habitability of ocean worlds is a priority of current and future NASA missions. The Europa Clipper mission will conduct approximately 50 flybys of Jupiter’s moon Europa, returning a detailed portrait of its interior from the synthesis of data from its instrument suite. The magnetometer on board has the capability of decoupling Europa’s induced magnetic field to high precision, and when these data are inverted, the electrical conductivity profile from the electrically conducting subsurface salty ocean may be constrained. To optimize the interpretation of magnetic induction data near ocean worlds and constrain salinity from electrical conductivity, accurate laboratory electrical conductivity data are needed under the conditions expected in their subsurface oceans. At the high-pressure, low-temperature (HPLT) conditions of icy worlds, comprehensive conductivity data sets are sparse or absent from either laboratory data or simulations. We conducted molecular dynamics simulations of candidate ocean compositions of aqueous NaCl under HPLT conditions at multiple concentrations. Our results predict electrical conductivity as a function of temperature, pressure, and composition, showing a decrease in conductivity as the pressure increases deeper into the interior of an icy moon. These data can guide laboratory experiments at conditions relevant to icy moons and can be used in tandem to forward-model the magnetic induction signals at ocean worlds and compare with future spacecraft data. We discuss implications for the Europa Clipper mission.

Hydrogen cyanide (HCN)-derived molecules and polymers are featured in several hypotheses on the origin of life. Over half a century of investigations into HCN self-reactions have led to many suggestions regarding the structural nature of the products and an even greater number of proposed polymerization pathways. A comprehensive overview of possible reactions and structures is missing. In this work, we use quantum chemical calculations to map the relative Gibbs free energy of most HCN-derived molecules and polymers that have been discussed in the literature. Our computed free energies indicate that several previously considered polymerization pathways are not spontaneous and should be discarded from future consideration. Among the most thermodynamically favored products are polyaminoimidazole and adenine.

Reactive transport modeling is a critical tool for elucidating the coupling among geochemical reactions, transport processes, and fracture permeability. This study explores the implications of preferential clay-rich regions near fracture surfaces of a Mancos shale sample on the reactive evolution of the fracture by using reactive transport simulations. These simulations utilized heterogeneous mineralogy data obtained from an in-depth analysis of a clay-rich region near the fracture surface, sourced from a mechanically induced fracture. We compared these simulations with counterparts assuming homogeneous mineral distributions based on bulk X-ray diffraction (XRD) data and prior imaging of the sample matrix. The results consistently show increased reactivity in cells near the inlet and fracture surface across all scenarios. The most significant changes in the porosity, mineral composition, and ion concentration occur in cells adjacent to the fracture at the system inlet. Comparative analysis reveals variations in mineral and porosity evolutions among the three systems. Over longer simulation periods, dissolution and porosity increase occur more rapidly in simulations, reflecting mineral heterogeneity, particularly within the clay-rich region near the fracture. A sensitivity analysis of mineral surface area (SA) values shows consistent trends using both low and high Brunauer–Emmett–Teller (BET) SA values over short time scales (days) but substantial disparities over longer time scales (years). These findings hold promise for improving our ability to predict the evolution of reactive fractures, with implications for subsurface CO₂ sequestration and oil recovery. In summary, this study advances our understanding of reactive transport in fractured systems, offering new avenues for predictive modeling.

Laser-induced breakdown spectroscopy (LIBS) offers a noninvasive, label-free technique for chemical analysis in challenging environments, including for deep-sea mineral resource evaluation and extra-terrestrial geology. We aim to improve the usefulness of LIBS spectral analysis in these applications. We propose an efficient, systematic procedure that uses calibration-free LIBS (CF-LIBS) to quantitatively estimate chemical compositions. This method combines baseline estimation and denoising using sparsity with the spectrum-adapted expectation–conditional maximization algorithm, enabling nonlinear background subtraction and high-throughput peak fitting. In addition, we introduce a Boltzmann plot regression based on Student’s t-distribution that is robust against outliers. These techniques allow the chemical composition of metal and rock samples to be estimated using the CF-LIBS method, demonstrating its potential for use in comprehensive geological surveys in deep-sea and extra-terrestrial environments.

Methoxymethanol (CH₃OCH₂OH), an oxygenated volatile organic compound of low stability detected in the interstellar medium, represents an example of nonrigid organic molecules showing various interacting and inseparable large-amplitude motions. The species discloses a relevant coupling among torsional modes, strong enough to prevent complete assignments using effective Hamiltonians of reduced dimensionality. Theoretical models for rotational spectroscopy can improve if they treat three vibrational coordinates together. In this paper, the nonrigid properties and the far-infrared region are analyzed using highly correlated ab initio methods and a three-dimensional vibrational model. The molecule displays two gauche–gauche (CGcg and CGcg′) and one trans–gauche (Tcg) conformers, whose relative energies are very small (CGcg/CGcg′/Tcg = 0.0:641.5:792.7 cm^–1). The minima are separated by relatively low barriers (1200–1500 cm^–1), and the corresponding methyl torsional barriers V₃ are estimated to be 595.7, 829.0, and 683.7 cm^–1, respectively. The ground vibrational state rotational constants of the most stable geometry have been computed to be A₀ = 17233.99 MHz, B₀ = 5572.58 MHz, and C₀ = 4815.55 MHz, at ΔA₀ = −3.96 MHz, ΔB₀ = 4.76 MHz, and ΔC₀ = 2.51 MHz from previous experimental data. Low-energy levels and their tunneling splittings are determined variationally up to 700 cm^–1. The A/E splitting of the ground vibrational state was computed to be 0.003 cm^–1, as was expected given the methyl torsional barrier (∼600 cm^–1). The fundamental levels (100), (010), and (001) are predicted at 132.133 and 132.086 cm^–1 (methyl torsion), 186.507 and 186.467 cm^–1 (O–CH₃ torsion), and 371.925 and 371.950 cm^–1 (OH torsion), respectively.

Wildfires are increasing in frequency and intensity, with increasing impacts on air quality and climate. A main component of smoke is biomass-burning organic aerosol, BBOA, including both primary OA (POA) and secondary OA (SOA). Here, we provide wildfire-relevant SOA yields for the reactions of 5 BB volatile organic compounds (VOCs) that have been predicted to lead to substantial SOA formation (phenol, catechol, styrene, furfural, and methyl furfural). Reactions were conducted in a large Teflon chamber with OH under high-NO conditions. We focus specifically on providing SOA yields and volatility basis sets (VBSs) that can be applied to ambient data, including at high OA concentrations in large plumes. We introduce a new method for obtaining VBSs while accounting for Teflon environmental chamber wall effects and for changes in temperature during experiments. Vapor wall loss corrections increase SOA by ∼30% across different systems. The SOA from this work is estimated to evaporate faster upon dilution than POA. We also analyze mass spectra from particle-phase measurements, which confirm the presence of SOA species identified by other researchers, and report nitrocatechol mass yields for phenol (38%) and styrene (0.45%).

Hydrogen cyanide (HCN), a key molecule of significant importance in contemporary perspectives on prebiotic chemistry, originates in planetary atmospheres from various processes, such as photochemistry, thermochemistry, and impact chemistry, as well as from delivery by impacts. The resilience of HCN during periods of heavy bombardment, a phenomenon caused by an influx of material on unstable trajectories after accretion, remains relatively understudied. This study extensively investigates the stability of HCN under impact conditions simulated using a laboratory Nd:YAG laser in the ELISE experimental setup. High-resolution infrared spectroscopy was employed to monitor the gas phase composition during these simulations. Impact chemistry was simulated in bulk nitrogen atmospheres with varying mixing ratios of HCN and water vapor. The probed range of compositions spans from ∼0 to 1.8% of HCN and 0 to 2.7% of H₂O in a ∼1 bar nitrogen atmosphere. The primary decomposition products of HCN are CO and CO₂ in the presence of water and unidentified solid phase products in dry conditions. Our experiments revealed a range of initial HCN decomposition rates between 2.43 × 10¹⁵ and 5.17 × 10¹⁷ molec J^–1 of input energy depending on the initial composition. Notably, it is shown that the decomposition process induced by the laser spark simulating the impact plasma is nonlinear, with the duration of the irradiation markedly affecting the decomposition rate. These findings underscore the necessity for careful consideration and allowance for margins when applying these rates to chemical models of molecular synthesis and decomposition in planetary atmospheres.

The uptake of glyoxal (Gly) on 28 different samples with varying mineralogical origins, such as clays, mineral proxies, and natural dusts from the major arid regions of the Earth, was determined. Experiments were performed at ambient temperature inside a Knudsen flow reactor coupled to a molecular-beam-sampling mass spectrometer. The objective of using a such high number of mineral surfaces (screening approach) was to identify composition–activity relationships (CAR) that link the elemental composition of the mineral samples with the Gly uptake and to evaluate the impact of particle size on Gly uptake. Three parameters were measured to meet these objectives: (i) the initial uptake coefficient (γ₀), (ii) the quasi-steady-state uptake coefficient (γ_q–ss), and (iii) the number of Gly molecules taken up (or uptake quantity, Ns, in molecules cm^–2). In all of the various investigated Gly-surface systems, Gly uptake was found to be predominantly irreversible. The γ₀ values measured indicate that Gly is selectively uptaken on surface sites terminated with hydroxyl groups. The abundance of elements, such as Ti, Al, and Ca, was evidenced to play a dominant role in the uptake of Gly on mineral dusts. In particular, the CAR trends observed were: ${\gamma }_0=(0.05\pm 0.02)+(7.2\pm 2.0)\times \frac{Ti}{\mathrm{Si}}$, ${\gamma }_{q‐\mathrm{ss}}=(16.7\pm 2.2)\times {10}^{-7}-(20.0\pm 6.5)\times \mathrm{ex}{p}^{[(-15\pm 9)\times (\mathrm{Al}+\mathrm{Ca})/\mathrm{Si}]}$, where the relative abundance of the elements is expressed in % wt for a constant Gly concentration of 70 ppb. Our results suggest that Gly is taken up on mineral dust particles, and thus, this heterogeneous process can contribute to the formation of secondary organic aerosols (SOA) in the atmosphere. Furthermore, our results reveal the need of composition–activity relationships for atmospheric pollutants that if implemented in atmospheric models will assist in better simulating the atmospheric aging of mineral dust. Finally, the steady-state uptake coefficients of Gly on Gobi natural dust were determined as a function of Gly concentration and results were found to be well represented by the expression γ_q–ss = (1.3 ± 0.4) × 10^–6 + (5.1 ± 0.2) × 10^–5 [Gly]^{−(0.85±0.04)}, wher

Locating and developing ideal sites for large-scale capture and storage of carbon dioxide has become increasingly necessary due to increasing global emissions and warming. Mafic–ultramafic rocks present a unique geologic setting as they can trap injected CO₂ in pore space, mineralize that CO₂ to permanently store it as carbonate minerals, and simultaneously release critical minerals. However, these reservoirs are undercharacterized relative to sedimentary carbon storage settings. In this study, we execute a methodology for determining carbonation and critical mineral recovery potential in mafic–ultramafic reservoirs. Using an olivine-rich basalt from the island of Hawai’i, we performed petrologic and geochemical analyses to determine its chemistry, mineralogy, and pore network architecture. We use this data to first quantify the nonreactive storage resource potential and determine the bulk storage of 50 MMT of CO₂ in the pore space of a basalt volume test case, along with realistic P10, P50, and P90 scenarios for that same volume. Then, using the chemistry and mineralogy, we both estimate the total mineralization and critical mineral recovery potential, as well as more realistic values based on dissolution–precipitation reactions at the surface areas of pores. This storage resource estimate methodology can assist in accelerating the global commercialization of geologic carbon storage and critical mineral recovery.

The adsorption of rare earth elements (REEs) to iron oxides can regulate the mobility of REEs in the environment and is heavily influenced by water chemistry. This study utilized batch experiments to examine the adsorption of Nd, Dy, and Yb to goethite under varying pH, electrolyte (type and concentration), and concentrations of dissolved inorganic carbon and citrate. REE adsorption was strongly influenced by pH, with an increase from essentially no adsorption at pH 3.0 to nearly complete adsorption at pH 6.5 and higher. Citrate enhanced the adsorption of REEs at low pH (<5.0), likely by forming goethite-REE-citrate ternary surface complexes. However, citrate inhibited the adsorption of REEs at higher pH (>5.0) by forming aqueous REE-citrate complexes. Ionic strength had a small influence on REE adsorption, and the presence of dissolved inorganic carbon had no discernible effect. Equilibrium adsorption was interpreted with a triple-layer surface complexation model (SCM). The selection of surface complexation reactions was guided by extended X-ray absorption fine structure spectra. An SCM with a single bidentate inner-sphere surface complexation reaction for Nd and two inner-sphere surface complexation reactions (one monodentate and one bidentate reaction) for Dy and Yb effectively simulated adsorption across a broad range of conditions in the absence of citrate. Accounting for the effects of citrate on REE adsorption required the addition of up to two ternary REE-citrate-goethite surface complexes. The SCM can enable predictions of REE transport in subsurface environments that have goethite as an important adsorbent mineral. This predictive capability could contribute to identifying potential REE sources and facilitating efficient extraction of REEs.