We present here new experimental data on H 2 O-CO 2 solubility in mafic melts with variable chemical compositions (alkali basalt, lamproite and kamafugite) that extend the existing database. We show that potassium and calcium-rich melts can dissolve ~ 1 wt% CO 2 at 3500 bar (350 MPa) and 1200°C, whereas conventional models predict solubilities of 0.2-0.5 wt%, under similar P-T conditions. These new data, together with those in the literature, stress the fundamental control of melt chemical composition on CO 2 solubility. We present a semiempirical H 2 O-CO 2 solubility model for mafic melts, which employs simplified concepts of gas-melt thermodynamics coupled with a parameterization of both chemical composition and structure of the silicate melt. The model is calibrated on a selected database consisting of 289 experiments with 44 different mafic compositions. Statistical analyses of the experimental data indicate that, in mafic melts, the chemical composition and therefore the structure of the melt plays a fundamental role in CO 2 solubility. CO 2 solubility strongly depends on the amount of non-bridging oxygen per oxygen (NBO/O) in the melt, but the nature of the cation bonded to NBO is also critical. Alkalis (Na+K) bonded to NBO result in a strong enhancement of CO 2 solubility, whereas Ca has a more moderate effect. Mg and Fe bonded to NBO have the weakest effect on CO 2 solubility. Finally, we modelled the effect of water and concluded that H 2 O dissolution in the melt enhances CO 2 solubility most likely by triggering NBO formation. In contrast with CO 2 but in agreement with earlier findings, H 2 O solubility in mafic melts is negligibly affected by melt composition and structure: it only shows a weak correlation with NBO/O.
On the NASA 2020 rover mission to Jezero crater, the remote determination of the texture, mineralogy and chemistry of rocks is essential to quickly and thoroughly characterize an area and to optimize the selection of samples for return to Earth. As part of the Perseverance payload, SuperCam is a suite of five techniques that provide critical and complementary observations via Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), visible and near-infrared spectroscopy (VISIR), high-resolution color imaging (RMI), and acoustic recording (MIC). SuperCam operates at remote distances, primarily 2–7 m, while providing data at sub-mm to mm scales. We report on SuperCam’s science objectives in the context of the Mars 2020 mission goals and ways the different techniques can address these questions. The instrument is made up of three separate subsystems: the Mast Unit is designed and built in France; the Body Unit is provided by the United States; the calibration target holder is contributed by Spain, and the targets themselves by the entire science team. This publication focuses on the design, development, and tests of the Mast Unit; companion papers describe the other units. The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data.
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