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A solar-powered spacecraft that spans the width of a basketball court and makes long, looping orbits around giant planet Jupiter. Its cloud-piercing instruments unlock a variety of secrets hiding within: how Jupiter came to be, its deep structure, its evolution over billions of years.

Science discoveries: Top 10

10. Water mystery, solved

The now-departed Galileo spacecraft dropped a probe into Jupiter’s atmosphere in 1995 and found it unexpectedly dry. Did Jupiter’s atmosphere possess 10 times less water than scientists expected? Juno’s answer: No. Nearer Jupiter’s equator, water is much more abundant.

Jupiter
The JunoCam imager aboard NASA's Juno spacecraft captured this image of Jupiter's southern equatorial region on Sept. 1, 2017. The image is oriented so Jupiter's poles (not visible) run left-to-right of frame.
Credits: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill
Full image and caption

9. New cyclone

On a close flyby, passing less than 2,200 miles (3,500 kilometers) above Jupiter’s cloud tops, Juno dodged Jupiter’s shadow to avoid freezing. Then the spacecraft discovered a new, giant cyclone at Jupiter’s south pole. A pattern of six cyclones, with one in the center, had seemed locked in place, but a new cyclone had somehow muscled in. (December 2019)

8. Lightning

Earlier NASA spacecraft — Voyagers 1 and 2, Galileo and Cassini — found lightning in Jupiter’s clouds by listening for their radio noise. Unlike Earthly lightning, Jupiter’s strikes were detected only at lower radio frequencies. But Juno — probably thanks to its closer approach — picked up higher-frequency lightning as well, resolving a 40-year-old conundrum. (June 2018)

7. Nine-storm north pole

A central cyclone at Jupiter’s north pole is surrounded by eight more, as if they’re bowing in tribute.These cyclones range from 2,500 to 2,900 miles across (4,000 to 4,600 kilometers). Their spiral arms smack together as they spin, but the storms don’t merge, Juno data shows. (March 2018)

composite infrared image of cyclones on Jupiter
This composite infrared image, derived from data collected by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard NASA’s Juno mission to Jupiter during a Feb. 2, 2017, pass over the planet, shows the central cyclone at the planet’s north pole and the eight cyclones that encircle it.

6. The Great Red Spot — in 3D

Maybe the most iconic storm in the solar system, Jupiter’s Great Red Spot has been swirling for centuries. But it appears to be slowly shrinking, from twice Earth’s size in 1979 to 1.3 times now. Juno plumbed the Great Red Spot’s depths, showing that its roots are 200 miles (320 kilometers) deep — 50 to 100 times as deep as Earth’s oceans. (December 2017)

5. Jolts from the poles

High-voltage electrical charges contribute to the formation of auroras at Jupiter’s poles, just as they do on Earth. But Jupiter is the solar system’s Texas: everything’s bigger. The most powerful energies there come to 400,000 electron volts, while our most powerful auroras on Earth hit only a few thousand volts. (September 2017)

4. Swarms of storms

Ranking high among the spectacular discoveries by the JunoCam imager, which takes pictures in visible light, are clusters of swirling, Earth-size storms at both of Jupiter’s poles. (May 2017)

3. Jupiter’s beltways

The cloud bands, or belts and zones, we can see from Earth have an intricate structure up close. Near the equator, they penetrate into the deepest parts of Jupiter’s atmosphere. But as you move closer to the poles, these belts tend to shapeshift into other structures. (May 2017)

2. Outstanding in its field

Scientists knew Jupiter had an intense magnetic field. Juno showed it is far more intense than anyone expected — and also bumpier. This field is 10 times stronger than Earth’s strongest, according to Juno’s magnetometer investigation instrument. (May 2017)

1. First close glimpse of the north pole

As Juno moved into its polar orbit around Jupiter, JunoCam provided the first clear, cose-up pictures of the north pole — a strange, bluish region full of giant storms and strange weather. Unlike Saturn, Jupiter doesn't display a weird hexagonal jet stream at its north pole. (September 2016)

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