NASA Juno spacecraft sheds light on Jovian atmospheric features

Saul Bowman
March 10, 2018

But where winds are blowing west, it's akin to slowing the spin of that part of Jupiter, changing the shape of the planet in different places.

Juno spends much of is time far out of reach from the worst of the planet's intense radiation belts, but swoops in once every orbit to focus on the planet beneath the stormy clouds on the surface.

On a gas planet, such an asymmetry can only come from flows deep within the planet; and on Jupiter, the visible eastward and westward jet streams are likewise asymmetric north and south. But what lies beneath?

"None of the models predicted that it would go that deep", Bolton said. Other believed that these thick clouds were instead quite shallow, just occupying the first few hundred kilometers of Jupiter's atmosphere. No one knew for sure-until now.

To tackle this question, Juno measured Jupiter's gravitational field.

The mission also found that the planet's interior rotates as a solid body, despite its fluid nature. The planet's clouds, with their intricate eddies and swirls, look like something out of Van Gogh's Starry Night (which was actually mankinds first image of the Andromeda Galaxy).

An worldwide team of researchers analysed data from the Juno spacecraft and found a constellation of nine extremely powerful cyclones over Jupiter's north pole and six over the south pole. Similar studies into data gathered from the Cassini probe may soon tell us whether the same underlying planetary dynamics are at play when it comes to Saturn, too. Essentially, the resulting force of Jupiter's rotation around its axis should produce a perfectly symmetric "bulge" around the equator. This gravitational asymmetry is caused by hydrogen-rich gas is flowing asymmetrically deep in the planet, and Juno was able to study this process. Juno carries no instrument capable of directly measuring such asymmetries, but they should manifest as subtle alterations in the spacecraft's motion as it moves through its 53-day polar orbit around the planet. The antenna beams radio waves from Earth, which Juno's transponder receives and sends back. "The remarkable thing about this", said Galanti, "is that we were able to directly measure the signature of the flows themselves".

Juno also snapped some awe-inspiring images of the massive cyclones that rage at Jupiter's poles. An independent analysis by William Folkner and colleagues at the NASA Jet Propulsion Laboratory verified the hard measurement. Corresponding Author: Tristan Guillot (Université Côte d'Azur, Nice, France). This jet stream contains an estimate of 1 percent of the planet's entire mass.

Jupiter is a gas giant with a radius of about 70,000 km (11 times that of the Earth) and a composition very similar to that of the Sun, largely hydrogen and helium.

Remarkably, these predictions are already being tested. In fact, they say we may be creating a generation of drivers who lack respect for the road. Recent data from Juno shows us that neither is the case. "The picture that is emerging from Cassini is that of a planet very different from Jupiter".

The results have been analyzed in a paper published in Nature on Wednesday. Provided their spacecraft stays healthy and funded, the Juno team is contemplating additional measurements that could further probe Jupiter's interior, such as monitoring tidal bulges raised by large moons whipping around the planet. "Earth's atmosphere is less than one millionth of the total mass of Earth", Yohai Kaspi, lead author of the research, explains.

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