Jupiter is the first planet other than Earth seen to host what appear to be atmospheric light shows called “sprites” or “elves.”
These two types of atmospheric glows form when lightning alters electric fields in the atmosphere above a storm. On Earth, these events cause high altitude nitrogen molecules to glow red for a moment. Sprites appear in the mesosphere, at heights of about 50 to 90 kilometers (31 to 56 miles). They can light up the sky for tens of kilometers (miles). Elves are far bigger. They can span hundreds of kilometers. They also form at greater heights — 75 to 105 km. That’s solidly within the lower thermosphere.
Scientists thought sprites and elves also might dance above other planets that crackle with lightning. But until now, no one had glimpsed these lights on another world.
NASA’s Juno spacecraft started orbiting Jupiter in 2016. Since then, Juno has seen 11 flashes of light on the gas giant that could be sprites or elves. These flares appeared above Jupiter’s water clouds, where most lightning forms. Juno saw several in regions known to be stormy.
Each flash lasted milliseconds. That’s about as long as sprites and elves last on Earth. And the flashes glowed in ultraviolet light. This is the wavelength band in which any sprites or elves on Jupiter would be expected to glow. It’s different from the red hues of sprites and elves on Earth. Why? Unlike Earth, Jupiter’s atmosphere is mostly hydrogen, not nitrogen.
Researchers reported the flashes online October 27 in the Journal of Geophysical Research: Planets.
Juno could confirm that these lights are sprites or elves with more observations, says Rohini Giles. She is a planetary scientist at the Southwest Research Institute in San Antonio, Texas. If Juno saw a lightning strike at the same place as one of these ultraviolet flashes, “that would prove it,” she says.
Juno may also reveal the size of those light shows if it manages a closer look at one of the flashes. Knowing how big they are could tell scientists which the lights are — sprites or elves. Or maybe even both.