New results from NASA’s Juno mission to Jupiter suggest that the sprites may have appeared in the upper atmosphere of the solar system’s largest planet. This is the first time that these bright, unpredictable, and extremely short bursts of light – formally known as transient light events or TLEs – have been observed on a planet other than Earth. The mission results are published in the Journal of Geophysical Research: Planets.
Sprites are a type of electrical discharge of cold plasma beating in the mesosphere and thermosphere. The sprites are difficult to distinguish, but they appear in a strong thunderstorm at an altitude of about 50 to 130 kilometers (the height of the formation of “ordinary” lightning is no more than 16 kilometers) and reach a length of up to 60 km and up to 100 km in diameter. The appearance of sprites was recorded only on Earth. They are often jellyfish-like in shape.
Scientists had previously predicted that these bright, ultra-fast flashes of light would be present in Jupiter’s vast, turbulent atmosphere, but their existence remained theoretical. Then, in the summer of 2019, researchers working with data from Juno’s Ultraviolet Spectrograph (UVS) discovered something unexpected: a bright, narrow band of ultraviolet radiation that disappeared in a flash.
The appearance of sprites and elves on Jupiter has been predicted by several previously published studies. According to these predictions, 11 large-scale bright events detected by the UVS Juno instrument occurred in the region where lightning is known to form. Juno scientists could also rule out that they were just mega-lightning, because they were found about 300 kilometers above the site where most of Jupiter’s lightning occurs. And UVS recorded that hydrogen emissions predominated in the spectra of bright flares, which is typical for sprites.
Comparing sprites from Jupiter to those from Earth will help scientists better understand electrical activity in planetary atmospheres.