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The lightning phenomenon known as a sprite depicted on Jupiter in this illustration. Jupiter’s hydrogen-rich atmosphere would likely make them appear blue. In the Earth’s upper atmosphere, the presence of nitrogen gives them a reddish color. Credit: NASA / JPL-Caltech / SwRI
An instrument on the spacecraft may have detected transient light events – bright flashes of light in the gas giant’s upper atmosphere.
New results of POTJuno mission in Jupiter suggest that “goblins” or “elves” could be dancing in the upper atmosphere of the largest planet in the solar system. It is the first time that these extremely brief, unpredictable, bright flashes of light, formally known as Transient Light Events, or TLEs, have been observed on another world. The findings were published on October 27, 2020, in the Journal of Geophysical Research: Planets.
Scientists predicted that these bright, ultra-fast flashes of light should also be present in Jupiter’s immense turbulent atmosphere, but their existence remains theoretical. Then, in the summer of 2019, researchers working with data from Juno’s ultraviolet spectrograph (UVS) instrument discovered something unexpected: a bright, narrow band of ultraviolet emission that disappeared in an instant.
Jupiter’s south pole and a possible transient light event – an extremely brief, unpredictable, bright flash of light – are seen in this annotated image of data acquired on April 10, 2020 from Juno’s UVS instrument. Credit: NASA / JPL-Caltech / SwRI
“UVS was designed to characterize the beautiful northern and southern lights of Jupiter,” said Giles, a Juno scientist and lead author on the paper. “But we found UVS images that showed not only the Jovian aurora, but also a bright flash of ultraviolet light in the corner where it was supposed to be. The more our team investigated, the more we realized that Juno may have detected a TLE on Jupiter. “
Short and bright
The sprites, named after a mischievous and resourceful character from English folklore, are transient light events triggered by lightning discharges from thunderstorms far below. On Earth, they occur up to 60 miles (97 kilometers) above intense and high thunderstorms and illuminate a region of the sky tens of miles wide, but last only a few milliseconds (a fraction of the time it takes you to blink).
Almost like a jellyfish, sprites feature a central light patch (on Earth, it is 15 to 30 miles, or 24 to 48 kilometers wide), with long tendrils that extend downward and upward. Elves (short for Light Emission and Very Low Frequency Disturbances Due to Electromagnetic Pulse Sources) appear as a flat disk shining in the Earth’s upper atmosphere. They also light up the sky for just milliseconds, but they can grow larger than sprites, up to 200 miles (320 kilometers) across on Earth.
Their colors are also distinctive. “On Earth, goblins and goblins appear reddish in color due to their interaction with nitrogen in the upper atmosphere,” Giles said. “But on Jupiter, the upper atmosphere is made up mostly of hydrogen, so they are likely to appear blue or pink.”
With three giant swords extending about 20 meters (66 feet) from its six-sided cylindrical body, the Juno spacecraft is a marvel of dynamic engineering, spinning to stay stable while making oval orbits around Jupiter. See the full interactive experience at Eyes on the Solar System.
Location, location, location
The appearance of goblins and elves on Jupiter was predicted by several previously published studies. Synchronizing with these predictions, the 11 large-scale bright events that Juno’s UVS instrument has detected occurred in a region where thunderstorms are known to form. Juno scientists were also able to rule out that these were simply mega-rays because they were found about 186 miles (300 kilometers) above the altitude where most of Jupiter’s rays form – its layer of water clouds. And UVS recorded that the spectra of the bright flashes were dominated by hydrogen emissions.
A rotating spacecraft powered by solar energy, Juno, arrived at Jupiter in 2016 after taking a five-year journey. Since then, it has made 29 scientific flybys of the gas giant, each orbit taking 53 days.
“We keep looking for more telltale signs of elves and goblins every time Juno takes a science pass,” Giles said. “Now that we know what we are looking for, it will be easier to find them on Jupiter and on other planets. And comparing the goblins and elves of Jupiter with those of Earth will help us better understand electrical activity in planetary atmospheres. “
Reference: “Possible Transient Light Events Observed in Jupiter’s Upper Atmosphere” by Rohini S. Giles, Thomas K. Greathouse, Bertrand Bonfond, G. Randall Gladstone, Joshua A. Kammer, Vincent Hue, Denis C. Grodent, Jean-Claude Gérard, Maarten H. Versteeg, Michael H. Wong, Scott J. Bolton, John EP Connerney and Steven M. Levin, October 27, 2020, Journal of Geophysical Research: Planets.
DOI: 10.1029 / 2020JE006659
More about the mission
JPL, a division of Caltech in Pasadena, California, manages the Juno mission for principal investigator Scott Bolton of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is administered at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. Lockheed Martin Space in Denver built and operates the spacecraft.
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