Juno Spacecraft’s First Results Shed Light on Jupiter’s Cyclones and Magnetic Field
published during a new moon.

In 2016, five years after it launched, the Juno spacecraft approached Jupiter. Since then, Juno has been busy gathering data from the planet’s poles and atmosphere, dipping down to roughly 3,000 miles over the clouds. Finally, researchers’ first analyses of the information gathered by Juno have been published in Science. While this is only the beginning of Juno’s Jovian insights, it’s a promising one. The initial studies reveal some surprises about Jupiter—namely, the presence of a much stronger magnetic field than scientists predicted, electron storms, and the existence of cyclones on the planet.

Juno Spacecraft's First Results

South pole. Credits: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles

Scott Bolton of the Southwest Research Institute and Principal Investigator of Juno is the lead author of the study that examines the planet’s climate features. Scientists had never gotten a glimpse at Jupiter’s poles before and didn’t expect to see so much movement there. Thanks to time-lapse imagery, researchers concluded that the oval-shaped objects are cyclones, some of which are nearly 900 miles wide. Thermal data from the atmosphere provides clues about how and why these cyclones form. Researchers believe high concentrations of atmospheric ammonia trigger these weather events.

Juno Spacecraft's First Results

Image of poles. Credit: J.E.P. Connerney et al., Science (2017)

Juno also collected information about Jupiter’s gravitational field—a critical piece of the planet’s atmospheric puzzle and one that will hopefully help scientists confirm the composition of its core, which scientists currently believe is solid. The findings indicate that the Jovian magnetic field is far more powerful than previously thought—approximately ten times stronger than that of Earth.

Juno Spacecraft's First Results

Credit: J.E.P. Connerney et al., Science (2017)

NASA astrophysicist John Connerney led that study, which focuses on area particularly affected by the magnetic field. When Juno first entered this region in June of 2016, it encountered a bow shock, or a boundary formed between the Jovian magnetosphere and the solar wind—in this area, solar wind speeds decrease dramatically as the magnetosphere takes over. What’s strange about this particular interaction is that Juno only hit a single bow shock, which scientists believe means the magnetosphere was—and perhaps still is—growing in size.

Juno Spacecraft's First Results

Southern Pole Aurora in infrared. Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM

Data from Juno also indicates the presence of electron beams over the poles, which trigger the aurorae previously imaged by the spacecraft. The showers of electrons work differently on Jupiter than they do on Earth. Generally, such electrons come from space, but on Jupiter, they seem to come from the atmosphere itself—another surprise yielded by Juno.

Juno Spacecraft's First Results

Northern Pole Aurora. Credit: NASA/ESA/John Clarke (University of Michigan)

While exciting, these results indicate how much we have yet to learn about Jupiter and its cosmic relationships. Thankfully, Juno is up to the task. “Every 53 days, we go screaming by Jupiter, get doused by a fire hose of Jovian science, and there is always something new,” says Bolton. Juno’s next mission is to examine the Great Red Spot—the flyby will occur on July 11. According to Bolton, “If anybody is going to get to the bottom of what is going on below those mammoth swirling crimson cloud tops, it’s Juno and her cloud-piercing science instruments.”