Juno mission reveals Jupiter’s extreme weather

Eight months after completing its first pass around Jupiter, NASA’s Juno probe is paying dividends in the form of some intriguing insights into the giant marbled planet.

The results obtained from Juno’s maiden orbit of Jupiter challenge previously held assumptions about the planet, including theories about its structure and magnetic field, according to two reports published in Science.

The first report, by Scott Bolton and his colleagues from the Southwest Research Institute in San Antonio, Texas, examines information Juno gathered from just above Jupiter’s cloud tops.

Key findings include confirmation that immense cyclones, up to 1,400 km in diameter, swirl around Jupiter’s poles. Still images of the previously unseen poles show the cyclones as bright ovals. 

Even more dramatically, thermal imaging of the planet shows unexpected structures that Bolton and his colleagues believe are giant weather systems caused by ammonia welling up from the deep atmosphere.

The measurements of Jupiter’s magnetic field they report are particularly surprising, suggesting the gas giant’s magnetic field is substantially stronger than previously estimated, at about 7.766 Gauss – 10 times the strength of Earth’s.

In the second study, a team headed by John Connerney of NASA’s Goddard Space Flight Centre report on the data Juno picked up from Jupiter’s magnetosphere – the region around the planet dominated by its magnetic field.

Connerney and his colleagues have used this information to deduce that Jupiter’s magnetic field was expanding when Juno first entered the planet’s magnetosphere. 

This deduction is because Juno only encountered one bow shock – a curved, stationary shockwave around the planet – during entry but ran into several more in its subsequent orbits. 

Connerney’s team was also able to examine the electron showers that strike Jupiter’s upper atmosphere, as Juno intercepted the beams of charged particles while above the Jovian poles. 

These showers are thought to be the cause of the enormous aurorae that occur above Jupiter; Connerney believes their alien distribution patterns indicate Jupiter’s interaction with its external environment is very different to current conceptual models.

While NASA launched Juno back in 2011, its real work has only just begun. Juno’s highly elliptical orbit enables it to get very close to Jupiter. Scientists hope it will continue to send home valuable data shedding light on the planet and the Solar System for many months to come.

Further reading

• Juno’s epic journey to probe Jupiter’s secrets