VfOx: Venus Oxygen Fugacity, the DAVINCI Student Collaboration Experiment

Knowledge of the atmospheric composition very near the Venus surface is required for assessing the stable mineralogy of the rocks present there. Oxygen fugacity (O2) of the near-surface atmosphere plays a key role in rock-gas chemical interactions. Current knowledge Venus near-surface O2 is not based on direct measurement, but on derivations from atmospheric observations of CO by Pioneer and Venera descent probes (to altitudes no lower than 12 km), extrapolations of CO gradients, knowledge of CO, O2, CO2 equilibrium chemistry, laboratory experiments on Earth, and kinetic modeling, resulting in a possible range of -19 to -22 (log10 O2). While DAVINCIs primary instruments will measure atmospheric constituents such as CO to high precision down to the lowest scale height of the atmosphere, from which O2 may be derived, the Venus Oxygen Fugacity (VOx) instrument will provide a direct measurement of oxygen partial pressure, independently corroborating atmospheric composition and constraining the stability zones of surface mineralogy. VOx measurements will be used to determine O2 below the clouds. Frequent measurements (on the order of 1/sec) will generate a profile down through the last hundreds of meters above the touchdown surface, where the atmosphere and surface should be in thermodynamic equilibrium and at the surface itself, should the Descent Sphere (DS) survive contact. VOx, DAVINCIs Student Collaboration Experiment (SCE), is a small single-objective sensor used to measure the partial pressure of molecular oxygen (O2) in Venus lower atmosphere. VOx is a simple sensor derived from off-the-shelf ceramic oxygen sensors and will be mounted on the outside of the DAVINCI DS. Throughout the duration of the mission, VOx will be designed, fabricated, tested, operated, and its results analyzed by undergraduate and graduate students mentored by the DAVINCI team in partnership with Johns Hopkins University and other programs, with an emphasis on building and encouraging STEM careers for underserved student populations. Learning through participation in an end-to-end experience is the objective for SCE participants. VOx flies to Venus as part of DAVINCI at the end of the 2020s, supported by several college generations of student scientists and engineers.