NASA's Juno spacecraft unveils dark origins of Jupiter's mysterious auroral storms for first time

The Juno spacecraft of the National Aeronautics and Space Administration (NASA) has revealed the dark origins of Jupiter's mysterious auroral storms, in a recent study.

The findings of the research, published in the journal AGU Advances state that the Ultraviolet Spectrograph instrument of the Juno mission, the gas-giant orbiter is illuminating the provenance of Jovian polar light.

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It reveals for the first time the birth of auroral dawn storms – the early morning brightening unique to Jupiter’s spectacular aurorae. These immense, transient displays of light occur at both Jovian poles and had previously been observed only by ground-based and Earth-orbiting observatories, notably NASA’s Hubble Space Telescope.

First discovered by Hubble’s Faint Object Camera in 1994, dawn storms consist of short-lived but intense brightening and broadening of Jupiter’s main auroral oval – an oblong curtain of light that surrounds both poles – near where the atmosphere emerges from the darkness in the early morning region.

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Before Juno, observations of Jovian ultraviolet aurora had offered only side views, hiding everything happening on the nightside of the planet. 

According to Bertrand Bonfond, a researcher from the University of Liège in Belgium and lead author of the study, “Observing Jupiter’s aurora from Earth does not allow you to see beyond the limb, into the nightside of Jupiter’s poles. Explorations by other spacecraft – Voyager, Galileo, Cassini – happened from relatively large distances and did not fly over the poles, so they could not see the complete picture.”

 “That’s why the Juno data is a real game-changer, allowing us a better understanding of what is happening on the nightside, where the dawn storms are born.”

Researchers found dawn storms are born on the nightside of the gas giant. As the planet rotates, the soon-to-be dawn storm rotates with it into the dayside, where these complex and intensely bright auroral features grow even more luminous, emitting anywhere from hundreds to thousands of gigawatts of ultraviolet light into space.

The jump in brightness implies that dawn storms are dumping at least 10 times more energy into Jupiter's upper atmosphere than typical aurora.

The interior of Jupiter is just as intriguing as the planet’s dazzling surface, with a swirling mixture of liquid hydrogen and helium at its centre, vast atmospheric jet streams and exotic gravitational properties.

Data from NASA’s Juno spacecraft, orbiting the solar system’s largest planet since 2016, is providing researchers with what they called unprecedented insight into Jupiter’s internal dynamics and structure. Until now, scientists have had scant information about what lies below Jupiter’s thick red, brown, yellow and white clouds.

Jupiter is a type of planet called a gas giant, as opposed to rocky planets like Earth and Mars, and its composition is 99 percent hydrogen and helium. Juno’s data showed that as you go deeper under the surface, Jupiter’s gas becomes ionized and eventually turns into a hot, dense metallic liquid.