NASA’s Juno mission reveals the depth and structure of Jupiter’s colorful bands and shrinking red spot

NASA’s Juno mission, the solar-powered robotic explorer of Jupiter, has completed its five-year prime mission to reveal the inner workings of the solar system’s biggest planet. Since 2016, the spacecraft has flown within a few thousand kilometers of Jupiter’s colorful cloud tops every 53 days, using a carefully selected array of instruments to peer deeper into the planet than ever before.

The most recent findings from these measurements have now been published in a series of papers, revealing the three-dimensional structure of Jupiter’s weather systems – including its famous Great Red Spot, a centuries-old storm big enough to swallow the Earth whole.

Before Juno, decades of observations had revealed the famous striped appearance of Jupiter’s atmosphere, with white bands known as zones, and red-brown bands known as belts. The bands are separated by powerful winds zipping east and west, known as the jet streams, and are punctuated by gigantic vortices, such as the red spot.

But scientists had long suspected that these weather patterns were the mere tip of the iceberg and that hidden and unforeseen phenomena might be shaping the atmosphere deep below the veil of clouds. Unlike the Earth, Jupiter’s atmosphere lacks a surface, so could be considered as a bottomless abyss.

Juno has three ways to peer down beneath the maelstrom of these cloudy upper layers. It can measure tiny changes to Jupiter’s gravity to sense the distribution of mass all the way down to the fuzzy core. It can measure Jupiter’s magnetic field to determine the flows within deep, magnetized fluid layers. And it can use microwave light to look straight through the clouds.

The Great Red Spot

Jupiter’s Great Red Spot has had a hard time in recent years. It has been steadily shrinking in the east-west direction for decades, and recent encounters with smaller vortices has led to enormous flakes of reddish material being drawn out of the spot itself. These flaking events, though troublesome for fans of the best-known storm in the solar system, do appear to be superficial, only affecting the reddish hazes that sit atop the vortex.

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