Sprite discharges on Venus, Jupiter and Saturn: a Laboratory Investigation in Planetary Gas Mixtures

Lightning was detected on several planets in the solar system, where it could also produce sprites in the upper layers of these atmospheres. Large sprite discharges at mesospheric altitudes on Earth have been found to be physically similar to streamer discharges in air at sea level density. Based on this understanding, we investigate possible sprite discharges on the Gas Giant planets and on Venus through laboratory experiments on streamers in H2-He and CO2-N2 mixtures. Streamer diameters, velocities, radiance and overall morphology are investigated for sprites on Jupiter, Saturn and Venus, by means of a fast ICCD camera. The spectra of the streamer discharges are measured; they are dominated by the minority species N2 on Venus, and by radiative dissociative continuum radiation of H2 in the Gas Giants. The spectrum of a fully developed spark on Venus and Saturn is also measured.