Climate models for Venus rely heavily on theoretical modeling and laboratory experimentation due to the extreme surface conditions of the planet and limited in situ surface data. To better explore the relative importance of reactions between the surface and the atmosphere on Venus, we exposed representative volcanic glasses and basaltic minerals to a large‐scale simulation of Venus surface conditions with a realistic atmospheric composition. This study consistend of two experiments of 42 and 80 days that replicated both physical conditions and atmosphere composition derived from available in situ near‐surface data using the Glenn Extreme Environment Rig (GEER) at the NASA Glenn Research Center. These experiments revealed significant reactivity of common Ca‐bearing pyroxenes (diopside and augite) to form anhydrite. Olivine and labradorite showed minimal reactivity. Volcanic glasses, including both natural and synthetic samples, were exceptionally reactive, rapidly forming both anhydrite and thénardite (Na2SO4), as well as transition metal sulfates (i.e., Cu, Cr), halite (NaCl), and sylvite (KCl). Our results document chemical and textural alteration of sample surfaces and provide sufficient evidence for an active sulfur sink on multiple samples, with sulfates as the dominant secondary mineralogy. These experiments suggest likely surface mineralogies and solid phases present on Venus' surface with significant implications for upcoming missions and provide new data for comparison to high‐temperature mineral–gas reactions prevalent on Venus, Earth, and Io.

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The lower Venusian atmosphere is the region from the surface to the cloud deck or about 0–50 km. Early modeling studies of the atmosphere were primarily based on thermodynamics; more recent modeling studies are based on kinetics of the elementary reactions. In this paper, we take the accepted nominal composition of near-surface gases at ∼42 km and show some of the constituents are indeed at thermodynamic equilibrium. We impose a small oxygen gradient and use a thermodynamic free energy minimization code to describe the vertical gradients of mixing ratios for the primary gases in the lower atmosphere. The oxygen gradient is within the measurement errors on oxygen and thus maintains mass conservation. Reasonable agreement is found between our calculations and the vertical profiles of H2O, H2SO4, OCS, H2S, and S n (n = 1–8). We then did a kinetic analysis of kinetic expressions for the formation of these species. Consistent with other investigators, we find that very few if any reactions should be at equilibrium in the lower atmosphere. Yet our equilibrium calculations do show some agreement with observations. We conclude that the available kinetic expressions likely need improvement and factors such as catalysis must be included to reflect actual Venus conditions.

Crust/atmosphere interactions are thought to play an important role in the Venus greenhouse climate [1]. Limited in situ analyses of the surface of Venus and minimal determination of major and minor constituents in the lower atmosphere provide inadequate insight into possible dominant solid/gas reactions that can occur. Prior experimental modeling provides conflicting hypotheses as to the importance and chemical stability of geologic mineral phases on the surface of Venus [2,3,4]. For this study, we exposed a matrix of geologic material including minerals, rocks, and glasses for 42 days to Venus surface conditions using the Glenn Extreme Environment Rig (GEER) at NASA Glenn Research Center.We exposed a total of 35 phases in carefully prepared sample chips, which weighed on average 40 mg and were roughly 1 square cm in size. Two opposing faces of each sample were polished to create a common surface texture for pre-and post-exposure electron microscopy. These samples were then attached to 316 stainless steel mounts using gold wire. We verified the mineralogy and crystallinity of each sample through powder x-ray diffraction for structure and crystallinity.The Glenn Extreme Environment Rig (GEER) at the NASA Glenn Research Center in Cleveland, OH, provides unparalleled high fidelity simulation of Venus atmospheric pressure, temperature and chemistry. The temperature and pressure for this experiment were kept at 460°C and 92 bar (1334 psi) for 42 days, thereby keeping the simulated atmosphere above the supercritical point for CO 2 and within accepted near-surface temperature and pressure conditions for Venus. The gas fill for the experiment included CO 2 , N 2 , SO 2 , OCS, H 2 O, CO, H 2 S, HCl, and HF (in descending order of abundance).We analyzed exposed and representative unexposed sample chips with secondary electron (SE) and electron backscatter imagery (BSE) on a FEI Helios 650 instrument along with an Oxford Inc. XEDS chemical analysis and FIB to determine if any alteration occurred. Each sample was removed from the stainless steel mounts and mounted with carbon tape to an aluminum SEM mount and coated with approximately 10 nm of palladium. The majority the alteration for the silicate phases was very minimal (on the sub-micron level) suggesting that if these phases are present on the surface of Venus, they apparently are likely slow to react and involved only in longer-term reactions.The most common secondary minerals formed in our experiments are sulfur-bearing compounds, suggesting that although sulfur-bearing gases are relatively minor atmospheric components, they play an exceptionally active role in crust/atmosphere interactions. For the synthetic amorphous phases, including synthetic glass manufactured to mimic surface XRF chemical abundances from the Venera 13 lander 2188