NASA’s Juno spacecraft has been puttering around the Jovian system for the last few years, taking images and measurements of the solar system’s largest planet. Juno reached the end of its pre-planned mission recently, but NASA renewed it for at least a few more years. There’s a lot to see on and around Jupiter, like the asteroid impact that Juno captured in 2020.
Jupiter is a massive planet with correspondingly massive gravitational pull. As such, it gets hit 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 it’s uncommon to see them. Giles is the lead author of a new study published in Geophysical Research Letters that lays out the case for this rare impact detection.
According to Giles, the bright flash from late 2020 stood out in the data. Juno spent a lot of time scanning Jupiter’s powerful magnetic field and aurorae, but the flash on April 10, 2020 had a different spectral signature. It lasted just 17 milliseconds, but that was much longer than Transient Luminous Events (TLEs) that are common in Jupiter’s upper atmosphere. The spectral characteristics were also quite different, as indicated by the probe’s Ultraviolet Spectrograph (UVS).
The conclusion reached by Giles’ team is that this bright flash (shown above) came from an asteroid or comet that fell into Jupiter’s atmosphere and exploded as it heated up. Based on the brightness of the flash, the team estimated the object had a mass of 550 to 3,300 pounds (249 to 1,496 kilograms), making it far too small to leave signs on the gas giant. In 1994, the comet Shoemaker-Levy 9 smacked into Jupiter, but it was more than a mile across. Teams following up after that impact found visible scarring and X-ray emissions that took months to vanish.
These impacts can have major effects on even large planets. Fifteen years after Shoemaker-Levy 9, that object was still responsible for 95 percent of the water in Jupiter’s stratosphere. If the unnamed 2020 impactor caused any local effects, Juno couldn’t detect them. Juno has a few more years to keep an eye out for more space rocks running into the planet, though.
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