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We Now Know What Lies Beneath Jupiter's Clouds

08 March 2018

One of the most breathtaking photos of Jupiter shows a "string of pearls" - a series of eight massive rotating storms on its surface.

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). The most famous feature of Jupiter is the Great Red Spot, but also noteworthy are the bands of light and dark clouds that make up what we can see of the planet from afar. But what lies beneath? The deeper the winds go, the larger the asymmetry.

Two other papers looked at different physical parameters of Jupiter. No one knew for sure-until now.

"Juno is only about one third the way through its primary mission, and already we are seeing the beginnings of a new Jupiter", Bolton said. By measuring the imbalance - changes in the planet's gravity field - their analytical tools would be able to calculate how deep the storms extend below the surface.

By monitoring how the whole planet rotates, scientists also discovered that below the 3000km level, Jupiter effectively spins as a rigid body - more slowly than the churning gas above.

Answering this question may help us understand how the solar system and its planets formed.

Juno revealed that "odd" gravity events, including turbulent jet streams, stretch down to around the 1,800 mile (3,000 km) mark, roughly one-twentieth of the planet's radius. The fundamentals of the technique are simple: As Jupiter whirls around its axis, the resulting force should raise a slight, perfectly symmetric bulge around the planet's equator. Deviations in this bulge would give us a confirmation of complex internal structures.

An artist's conception of the Juno spacecraft in orbit around Jupiter.

In the first paper, researchers led by Luciano Iess of the Sapienza University of Rome in Italy used Doppler data to study Jupiter's gravitational field.

The team's analysis was assisted by a high precision transponder that measures Juno's velocity down to 0.01mm/s accuracy, even while travelling at record speed orbits of 70 km/s. "This is one hundredth the speed of a snail!"

Nasa's Cassini mission to Saturn, which ended in 2017, provided similar data set for Saturn's gravitational field that is now being analysed, says Professor Jonathan Fortney, from the department of astronomy and astrophysics at the University of California. An independent analysis by William Folkner and colleagues at the NASA Jet Propulsion Laboratory verified the hard measurement.

This link was explored further by a team led by Yohai Kaspi of the Weizmann Institute of Science in Israel, which studied the asymmetry of Jupiter's magnetic field to determine the depth of its atmosphere. Both of these teams' analyses converged on the figure of approximately 3,000 kilometers as the lower boundary for the flows.

'Thankfully, Jupiter has a sibling, the gas-giant planet Saturn. "Our results imply that the outer differentially-rotating region should be at least three times deeper in Saturn and shallower in massive giant planets and brown dwarf stars". We know with Cassini data that Saturn has a single cyclonic vortex at each pole. The pair and their collaborators have reportedly submitted a paper detailing the findings to the journal Science. The mission is scheduled to end in July but could be extended. NASA might choose to extend it, but the spacecraft could still succumb any day to the intense radiation from the deadly halos of high-energy particles trapped around the planet by magnetic fields. During this time, they built mathematical tools to analyze the gravitational field data; these are what would enable the researchers to get a grasp on Jupiter's atmosphere.

This may not sound like a lot, but in comparison, Earth's atmosphere is less than a millionth of its total mass.

These and other upcoming studies could perhaps shed light on a newfound mystery, presented in a fourth paper published by members of the Juno team in Nature this week.

New images from NASA's Juno probe show clusters of cyclones on the planet's poles. But for reasons scientist can not yet explain, the tightly-clustered cyclones remain distinct, according to NASA. And any linkage they may have to the planet's deep dynamics is unknown.

Raging storms on Jupiter have long captured the imagination of mankind and a new study has revealed the depths to which these fiery events extend.

We Now Know What Lies Beneath Jupiter's Clouds