The NASA spacecraft tasked with uncovering the secrets of Jupiter, king of the planets, is running out of time. The Juno probe has already survived far longer than anticipated—its path around the solar system’s largest planet has repeatedly flown it through a tempest of radiation that should have corroded away its instruments and electronics long ago. And yet here it is: one of the greatest planetary detectives ever built, still pirouetting around Jupiter, fully functional.
But it may not be for long. September 2025 marks the end of Juno’s extended mission. Although it could get another reprieve—an extended-extended mission—the spacecraft cannot carry on forever. Eventually the probe is fated to plunge into Jupiter’s stormy skies, to lethal effect. Regardless of when that happens, the spacecraft’s legacy is indelible.
It revealed a whole different Jupiter than scientists thought they knew. Oddly geometric continent-size storms, in strange yet stable configurations, dance around its poles. Its heaviest matter seems to linger in its skies, while its abyssal heart is surprisingly light and fuzzy. Its innards don’t resemble the lasagnalike layers found in rocky worlds; they look more like mingling swirls of different kinds of ink.
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And Juno wasn’t simply trying to understand Jupiter. It set out to uncover how the entire solar system was born. Jupiter, after all, was the first planet to piece itself together after the sun exploded into existence. Hidden underneath the planet’s cloud tops, there is a recording of the beginnings of everything we see around us. “That’s the story behind why Juno was created: to go and look inside Jupiter every way we knew how, to try to figure out what happened in the early solar system that formed that planet—and what role that planet had in forming us,” says Scott Bolton, the mission’s principal investigator at the Southwest Research Institute in San Antonio, Tex.
Whenever a mission studies a planet or moon up close, “you’re going to be surprised” at what it finds, says Juno project scientist Steve Levin of NASA’s Jet Propulsion Laboratory. But what you really want is “to make the theorists throw everything out the window and start over.” Juno has torn up more textbooks than any other planetary science mission. “It’s been quite a ride,” Levin says. And scientists will never look at Jupiter, or the solar system, in the same way again.
Jupiter, the Roman god, was often up to no good. According to myth, he obscured his mischief with a blanket of clouds so that nobody could see what he was up to. His wife, though, had the power to see through these clouds and monitor his shenanigans. Her name was Juno.
In the late 1970s the two Voyager space probes gave humanity its first spectacularly detailed look at the gas giant. Unlike the deific Juno, they couldn’t see Jupiter’s buried secrets—but they were sufficiently inspiring for Bolton, who was a college student at the time. “I had been a huge Star Trek fan and had fantasized about traveling around and wondering what the rest of the universe was like,” he says. When someone from JPL gave a talk at his school and showcased Voyager 1’s jaw-dropping shots of Jupiter and its maelstroms, he was sold. “I’d never seen anything like it.”
Juno spotted numerous oval cyclones on Jupiter's southern pole. NASA/JPL-Caltech/SwRI/MSSS (image data); Betsy Asher Hall and Gervasio Robles (image processing)
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