Of all known planets and moons in the galaxy, Venus remains the most Earth-like in terms of size, composition, surface age, and distance from the Sun [1]. Although not currently habitable, Venus lies within the Sun's 'Goldilocks zone', and may have been habitable before Earth [2]. What caused Venus to follow a divergent path to its present hostile environment, devoid of oceans, magnetic field, and plate tectonics that have enabled Earth's long-term habitability? The proposed Venus Origins Explorer (VOX) would determine how the evolution of Earth's twin diverged, and enable breakthroughs in our understanding of terrestrial planet evolution and habitability in our own solar system - and others. The VOX mission concept consists of two flight elements: 1) an Atmosphere Sampling Vehicle (ASV), and 2) an Orbiter that accommodates the ASV and also provides global reconnaissance of Venus using just two instruments and a gravity science investigation. The ASV would be released shortly after Venus Orbit Insertion and dips into the well-mixed atmosphere at 112 km. It delivers an in situ atmospheric sample to the Venus Original Constituents Experiment (VOCE) to measure noble gases, revealing the source and evolution of Venus' volatiles. The Orbiter uses the Venus Emissivity Mapper (VEM) to map global surface mineralogy and search for active or recent volcanism. Venus Interferometric Synthetic Aperture Radar (VISAR) generates long-awaited high-resolution imaging and digital elevation models, and possible deformation maps with repeat-pass interferometry, a new tool for planetary science. Ka-band tracking increases the gravity field resolution, enabling global elastic thickness estimates. Using a low risk implementation and just three instruments plus gravity science, VOX conducts a comprehensive global investigation of Venus' dynamic surface. As described below, VOX meets and exceeds the science objectives prescribed in the National Academy of Sciences most recent Planetary Science Decadal Survey. VOX is the logical next mission to Venus because it: 1) addresses top priority atmosphere, surface, and interior science objectives; 2) produces key global datasets to enable comparative planetology; 3) provides high-resolution global topography, composition, and imaging necessary to optimize future landed missions; 4) creates opportunities for revolutionary discoveries and observations of ongoing Venus geological activity, over a three-year period from an orbital platform plus an in situ atmospheric sampling vehicle; and 5) fuels the next generation of scientists by providing 44 Tb of science data. Additionally, VOX offers NASA the ability to select and fly small sats at Venus by providing relay and the ability to trade aerobraking duration for additional mass capability.
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