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NASA’s Juno spacecraft will peer into Jupiter’s planet-sized storm tonight

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Spotting the Great Red Spot

A picture of Jupiter’s Great Red Spot, taken by Voyager 1.

After spending more than a year at Jupiter, NASA’s Juno spacecraft is about to fly over the planet’s most iconic landmark: the Great Red Spot. It’s a giant storm twice as wide as Earth that’s been brewing on Jupiter for hundreds of years. Now, Juno is going to get the closest ever view of this extraterrestrial cyclone.

The Great Red Spot is the most recognizable part of Jupiter, but there’s still a lot of mystery surrounding this massive storm. It’s unclear exactly how long it’s been around, for instance. Stargazers first noticed a large spot on Jupiter in the 1600s, according to NASA, though we don’t know if they were actually looking at the same feature. Either, way, the Great Red Spot has been continuously monitored since the early 1800s — and since then, scientists have been trying to understand how the storm works.

One idea is that the Great Red Spot persists because of something called vertical flows. These features transport gas from above and below the storm into the Great Red Spot’s center, constantly replenishing the energy needed to keep the gases churning. But that’s all based on computer models, and we still don’t know what causes the storm’s reddish color or how deep the spot goes.

Figuring out the true nature of the storm has been tough because of how Jupiter is structured. The giant planet is covered in gas clouds that hide what’s going on underneath the surface. Various NASA spacecraft have snapped pictures of the Great Red Spot, such as the Voyager probes in 1979 and Galileo in the 1990s, but none have been able to deduce what the storm’s structure is like deep below.

A rendering of NASA’s Juno spacecraft.
A rendering of NASA’s Juno spacecraft.
Image: NASA

That’s what makes Juno’s flyby so exciting: the probe, which inserted itself into Jupiter’s orbit on July 4th of last year, is equipped with instruments specifically designed to peer through Jupiter’s clouds. Already, Juno’s instruments have been able to tell us a lot about Jupiter’s interior structure, and that the planet is a truly dynamic and complex world.

Juno is taking a while to study Jupiter, though, because its orbit around the planet takes 53 days to complete. Originally, the spacecraft was supposed to maneuver itself into a shorter two-week orbit, but that plan was scrapped due to a problem with the vehicle’s engine. Juno is in a highly elliptical path around the planet, too — one that takes the spacecraft close to Jupiter’s surface for a few hours each orbit. It’s only during these close passes, called perijove passes, when Juno can get the bulk of its data.

Tonight will mark Juno’s seventh perijove pass at Jupiter, and the sixth one where data is collected. (Data wasn’t collected during the second pass because the vehicle went into safe mode just beforehand.) The spacecraft will make its closest approach at 9:55PM ET, where it will be just 2,200 miles above the planet’s cloudy surface. Then 11 and a half minutes later, Juno will move over the Great Red Spot, passing within 5,600 miles of the storm’s surface. The mission team guarantees that all eight instruments will be on, including the spacecraft’s camera, JunoCam. So expect some amazing science, along with more stunning images of one of the biggest storms in the Solar System.