NASA’s Juno spacecraft detects an asteroid impact on Jupiter

NASA’s Juno spacecraft has been circling the Jovian system for the past few years, taking images and measurements of the largest planet in the solar system. Juno recently reached the end of its pre-planned mission, but NASA has renewed it for at least a few more years. There is a lot to see on and around Jupiter, such as the asteroid impact captured by Juno in 2020.

Jupiter is a massive planet with a corresponding massive gravitational pull. As such, it is affected by a lot of space debris. However, Rohini Giles of the Southwest Research Institute says most of these small impacts are tiny and so short-lived that they’re rare to see. Giles is the lead author of a new study published in Geophysical Research Letters that presents the case for this rare impact detection.

According to Giles, the Brilliant Flash of late 2020 stood out in the data. Juno spent a lot of time scanning Jupiter’s powerful magnetic field and aurora, but the April 10, 2020 flash had a different spectral signature. It only lasted 17 milliseconds, but it was much longer than the transient light events (TLE) that are common in Jupiter’s upper atmosphere. The spectral characteristics were also very different, as indicated by the probe’s ultraviolet (UVS) spectrograph.

The conclusion Giles’ team came to is that this bright flash (pictured above) was from an asteroid or comet that fell into Jupiter’s atmosphere and exploded while heating up. Based on the brightness of the flash, the team estimated the object to have a mass of 550 to 3,300 pounds (249 to 1,496 kilograms), making it far too small to leave any signs on the gas giant. In 1994, Comet Shoemaker-Levy 9 struck Jupiter, but it was over a kilometer in diameter. Teams that followed after this impact found visible scars and X-ray emissions that took months to disappear.

These impacts can have major effects even on large planets. Fifteen years after Shoemaker-Levy 9, this object was still responsible for 95% of the water in Jupiter’s stratosphere. If the unnamed 2020 impactor was causing local effects, Juno could not detect them. However, Juno still has a few years to keep an eye out for other space rocks entering the planet.

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