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Following the recent detection of the oxygen green line airglow on Mars, we have improved the statistical analysis of the data recorded by the NOMAD/UVIS instrument on board the ExoMars Trace Gas Orbiter mission by summing up hundreds of spectra to increase the signal-to-noise ratio. This led to the observation of the OI 630 nm emission, the first detection in a planetary atmosphere outside the Earth. The average limb profile shows a broad peak intensity of 4.8 kR near 150 km. Comparison with a photochemical model indicates that it is well predicted by current photochemistry, considering the sources of uncertainty. The red/green line intensity ratio decreases dramatically with altitude as a consequence of the efficient quenching of O(1D) by CO2. Simultaneous observations of the green and red dayglow will provide information on variations in the thermosphere in response to seasonal changes and the effects of solar events. © 2021. American Geophysical Union., B.H. is a research associate and S.A. is a postdoctoral researcher of the Belgian Fund for Scientific Research (FNRS). ExoMars is a space mission of the ESA and Roscosmos. The NOMAD experiment is led by the IASB-BIRA, assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (The Open University). This project acknowledges funding from BELSPO, with the financial and contractual coordination by the ESA PRODEX Office (PEA grant numbers 4000103401 and 4000121493). M.A.L.-V. and J.-J.L.-M. were supported by grant number PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU) and by the Spanish Science Ministry Centro de Excelencia Severo Ochoa Program under grant number SEV-2017-0709. M.R.P. and J.P.M were funded by the UK Space Agency under grants ST/V002295/1, ST/V005332/1, ST/S00145X/1, and ST/R005761/1. G.B. thanks the Italian Space Agency through grant number 2018-2-HH.0.

info:eu-repo/semantics/published

CASTAway is a mission concept to explore our Solar System’s main asteroid belt. Asteroids and comets provide a window into the formation and evolution of our Solar System and the composition of these objects can be inferred from space-based remote sensing using spectroscopic techniques. Variations in composition across the asteroid populations provide a tracer for the dynamical evolution of the Solar System. The mission combines a long-range (point source) telescopic survey of over 10,000 objects, targeted close encounters with 10–20 asteroids and serendipitous searches to constrain the distribution of smaller (e.g. 10 m) size objects into a single concept. With a carefully targeted trajectory that loops through the asteroid belt, CASTAway would provide a comprehensive survey of the main belt at multiple scales. The scientific payload comprises a 50 cm diameter telescope that includes an integrated low-resolution (R = 30–100) spectrometer and visible context imager, a thermal (e.g. 6–16 μm) imager for use during the flybys, and modified star tracker cameras to detect small (~10 m) asteroids. The CASTAway spacecraft and payload have high levels of technology readiness and are designed to fit within the programmatic and cost caps for a European Space Agency medium class mission, while delivering a significant increase in knowledge of our Solar System.