The Juno spacecraft has now completed 10 of its 12 currently planned science orbits around Jupiter—and astronomers are finally starting to share what they're learning about the largest planet in our solar system.
So far, we've mostly just enjoyed breathtaking photographs sent back from the JunoCam instrument, a crowd-guided camera designed primarily to fill our never-ending thirst for the beauty of the universe. But the spacecraft is carrying a host of scientific instruments that are gathering precious data about Jupiter, trying to solve some of its longstanding mysteries.
We've already learned that the aurora that circle Jupiter's poles don't work the way we expected. They're incredibly bright, so scientists had assumed they were caused by basically the same natural mechanism that causes the brightest aurora we have on Earth. But Juno findings suggest that the phenomenon is actually caused by what makes Earth's very faintest light shows.
That realization has come thanks to a pair of instruments: the Jupiter Energetic Particle Detector Instrument, nicknamed JEDI, and the Jupiter Auroral Distribution Experiment, or JADE. But the duo is just one of seven different sets of instruments and experiments on board Juno.
One of those instruments studies the same region of Jupiter, the poles—and because Juno orbits from pole to pole rather than around the planet's middle, this tool is uniquely poised to make new discoveries about what's happening there. That's the Jovian Infrared Auroral Mapper, or JIRAM, which studies the polar atmosphere, trying to learn more about the mysterious "hot spots" that mark the planet.
Or consider the gravity detector, which is using a radio signal beamed back and forth between Earth and Juno in order to pick up tiny changes in the spacecraft's orbit (marked by the signal traveling a tiny bit more or less distant than expected). Those minute changes are caused by patches of Jupiter that have slightly higher or lower gravity. Measuring the fluctuations can tell scientists about the planet's inner structure.
That's one of the biggest mysteries about Jupiter right now: We aren't sure if the planet is gas and liquid through and through or if there's something solid buried deep within it. We've spent so long only being able to see the striped glory of the very top layer of its atmosphere that it's hard to think Juno and its suite of instruments won't learn something we never even imagined.
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