Variable oxygen airglow on Venus as a probe of atmospheric dynamics

THE venusian atmosphere exhibits two global-scale circulation patterns: an east–west super-rotation at altitudes above 100km and below 70 km, and a solar-locked circulation between these heights, in which material rises on the dayside of the planet, flows around to the nightside and descends near the antisolar point (local midnight). The region at which these two flows interact (∼95 km) is difficult to study, and existing data1 are either in conflict or indicate long-term dynamical changes. Here we present high-resolution images of an oxygen airglow that arises during down-welling at ∼95 km altitude on the nightside of Venus. Oxygen atoms are formed by photolysis of CO2 on the sunlit hemisphere, and are then transported to the nightside, where they recombine during descent. The newly formed molecular oxygen emits radiation to produce the airglow. We observe localized, short-lived regions of emission and neighbouring dark areas, demonstrating the potential of such observations to constrain atmospheric dynamics at this little-studied and important altitude in the venusian mesosphere.

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