Elucidating the Rate of Volcanism on Venus: Detection of Lava Eruptions Using Near-Infrared Observations

Abstract

Lava eruptions can be observed remotely on Venus' nightside using a near-infrared window at a 1.0-micrometer wavelength, i.e., radiation at this wavelength emitted from the planetary surface traverses through the thick Venus atmosphere and clouds. Due to the strong dependence of the intensity of thermal emission on temperature, a hot surface produced by a lava eruption emits intense radiation, with the intensity of the excess radiation depending on the surface area and temperature of the lava flow. The excess emission from the hot surface is blurred by clouds, yet a 1-km 2 1500-K basaltic lava lake and a 50-km 2 1000-K lava flow are readily detected using this technique. Rapid cooling of exposed lava results in excess surface radiation that is detectable for just one Earth day after the end of an eruption; hence short-term eruptions are only detectable on the side of the planet where night is occurring. Eruptions lasting more than half a Venus day (i.e., more than about 60 Earth days), however, are detectable across the globe as nighttime occurs sometime during this period for every such event. Due to limited observational geometries, a complete global survey of active volcanos cannot be achieved from Earth, and in fact, only about 10% of short-lived major volcanic eruptions are observable. Alternatively, a satellite orbiting high above Venus (∼6 Venus radii) could detect virtually all short-lived nighttime volcanic events, or about half the events expected to occur across the globe.