Jupiter may be one of the planets we can spot with the naked eye, but scientists have long puzzled over what lies beneath its swirling clouds — or inside its stormy Great Red Spot.
Last July, NASA’s Juno mission slipped into orbit around Jupiter to uncover new details about our largest planetary neighbor. Its first scientific results were published in May (in 46 separate papers), and two mission scientists say the data have yielded revelations — and more questions.
“As we're trying to probe the interior of the planet, we're really starting to get some surprises about what's going on, on the inside,” says Juno program scientist Jared Espley, “interesting surprises about how the magnetic field is produced, interesting surprises about how the core is distributed on the inside of the planet and how the different atmospheric parts ... are distributed inside the planet.”
In one twist, Juno sent back photos of Earth-sized cyclones storming across both of Jupiter’s poles. “These are unexpected,” Espley says. “We've got these really powerful bands and belts that we're all familiar with, but we see these cyclones that don't really look anything like what we see at the equator.”
Before Juno entered Jupiter’s orbit, so little was known about the planet’s composition that scientists worried its radiation levels could be high enough to fry Juno’s instruments. “That was the real nail-biter for us because we're going someplace that nobody has ever flown before,” says Heidi Becker, Juno radiation monitoring investigation lead.
Becker says the craft was built with a 400-pound metal vault to protect mission electronics — but another revelation? Jupiter has a lot less radiation than her team initially predicted, “actually 10 times less than we modeled it to be, very close to the planet,” she says. “So Juno's doing just great.”
Jupiter’s core has also yielded some unexpected details: “The magnetic field that comes from that interior is thought to be planetwide, but it also looks like there's very small spatial scale features,” Espley says. “So, that means that there is something much closer to the surface that's contributing to the magnetic field.”
The planet’s weird magnetic field only adds to the pile of scientific questions: “Whether or not there's a secondary dynamo, a secondary source of magnetic field closer to the surface in a layer of conducting material, or whether or not that main core just has lots of small-scale features that manifest themselves close to the surface, we frankly don't know yet,” Espley says.
Scientists will know more soon, as Juno continues to trace its elliptical path around Jupiter. Each 53-day orbit gives the spacecraft a brief, slightly different perspective on the planet — building what Espley calls “a web of observations.”
“When we come screaming in super close to the planet it lasts just a few hours, and then we go way out far into the space around Jupiter, [what] we call the magnetosphere and make interesting observations of the charged particles, the plasmas,” he says. “Every time we come in, Jupiter has rotated slightly … so, we see a different part of the planet.”
This summer, Juno will fly over Jupiter’s Great Red Spot, the storm that’s been swirling “for hundreds of years,” Espley says. “We're really looking forward to getting good observations — both superficially with our camera, but also especially with our instruments that can look inside of the planet and try and get an understanding of what's going on inside.”
And, both scientists say Juno has quite a bit of life left. “We're expecting to see Juno continue for the next few years,” Espley says. Eventually, though, the spacecraft will meet a glorious end: plummeting into the planet it spent years examining, to avoid polluting other space locales.
“We're going to have to make sure that we don't smash into some other body in that system and contaminate it,” Becker explains. “We're not a perfectly clean spacecraft. We brought a little bit of us along with it.”
For now, Juno remains locked in its orbit, gathering the data to satisfy our Jovian curiosity. Espley admiringly calls Juno and other space probes our “robotic extensions into the solar system.”
“We humans have created these things — we took the ingredients that make up us and changed them into robots, and they're out there looking for those ingredients out in the cosmos,” he says.
“So, it really does kind of give you an emotional connection to the cosmos as you're exploring.”
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