NASA’s Juno probe captures Jupiter as we have never seen it before

NASA’s Juno probe has sent back remarkable new pictures of giant planet Jupiter, including a look down onto its stormy polar regions. The robotic spacecraft’s unique polar orbit has allowed it to view Jupiter in ways never possible before.

View of Jupiter's south pole
NASA’s Juno spacecraft got this view, looking down onto Jupiter’s south pole from an altitude of 52,000 km (32,000 miles). The oval features visible within the swirling blue and brown clouds are cyclones up to 1,000 km (600 miles) wide. Many separate images taken with the JunoCam instrument over three orbits were combined to form the single picture. Image credit: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles

Juno is also on a trajectory that brings it closer to the planet than any previous probe. As it swoops over the cloud tops, it is taking close-up images in incredible detail. One astonishing picture just released by NASA, with the first batch of scientific results from Juno, reveals what it looks like to gaze down on Jupiter’s south pole. The view, compiled from many separate photos taken with the probe’s JunoCam, shows many swirling storms, including ovals that are cyclones the size of Earth.

The storms are more clustered together, around each of the poles, than NASA scientists expected. But the north pole looks quite different from the south pole, and it is not clear why.

See mighty Jupiter for yourself!

Another surprise has come from one of Juno’s experiments, called the Microwave Radiometer (MRW) which samples thermal radiation from deep in Jupiter’s atmosphere. It has found that the complex weather system of belts and bands that are seen in Jupiter’s ammonia-rich cloud tops continue hundreds of kilometres deep into the atmosphere, but are not uniformly mixed.

Jupiter's atmosphere
Juno’s Microwave Radiometer, which examines Jupiter’s atmosphere beneath the cloud tops, found that ammonia is not evenly mixed but can reach a depth of about 350 km (220 miles). Image credit: NASA/JPL-Caltech/SwRI

Juno has also found that Jupiter’s intense magnetic field, which was known to be the most powerful of any planet’s, is even stronger than expected and is also irregular in its shape, making it appear lumpy. The magnetic field sparks aurorae, or northern and southern lights, around the poles, just as on Earth, but Juno observations suggest that the process at Jupiter behaves differently.

Juno, which was launched on August 5, 2011, is on an elongated orbit that carries it swooping in low from the north pole to the south pole every 53 days. For two hours, it flies as low as 4,200 km (2,600 miles) above the clouds before being flung out to a safe distance once again.

The reason for this unusual, extended orbit is to protect the craft from too much bombardment by Jupiter’s powerful radiation. Even so, over a year, Juno is receiving the equivalent of more than 100 million dental X-rays, which would be enough to fry the electronics on an unguarded spacecraft.

But Juno’s sensitive equipment is shielded within a titanium vault that is a metre wide and which has walls a centimetre thick. It also spins slowly as it orbits, allowing different instruments to scan the planet and to make measurements deep inside the cloud layers.

Aurora over Jupiter
An image from Juno of the aurora over the south pole of Jupiter. Image credit: NASA/JPL-Caltech/SwRI

Juno is trying to discover how Jupiter formed and evolved to help scientists understand more about the formation of the Solar System. It is known to be made up mainly of hydrogen and helium and is expected to tell us about the cloud of gas and dust from which the Sun and planets formed.

Juno’s Principal Investigator, Dr Scott Bolton, of the Southwest Research Institute at San Antonio, Texas, spoke to Skymania about what his team was hoping to learn. He said: “Juno’s goal is to improve our fundamental understanding of how our Solar System formed. From previous missions and ground-based observations we’ve learned that Jupiter holds key secrets.

“We know that Jupiter represents most of the leftover material in the Solar System – the cloud of gas, dust and debris – after the Sun formed, billions of years ago. All of the planets, moons, comets and asteroids would fit inside Jupiter. So if we want to understand what the early Solar System was like, Jupiter is the best shot that we have.

Jupiter's cloud tops
Swirling features make Jupiter’s cloud tops resemble a work of abstract art in these images gathered by Juno in close flybys. Image credit: NASA/SWRI/MSSS/Gerald Eichstadt/Sean Doran

“It is primarily made of the same material that the Sun is made of – mostly hydrogen, a little bit of helium and a smidgen of all the other stuff – so we’re basically trying to discover the recipe for planets and our approach is to get the ingredient list from Jupiter.”

Because Jupiter rotates rapidly, once every 10 hours or so, Juno is flying over a different part of the planet on each pole-to-pole flyby. The next close pass, on July 11, will be especially exciting because the probe will fly directly over Jupiter’s most famous feature, the Great Red Spot. This should allow NASA scientists to peer inside the 16,500 km (10,250 mile) wide, anti-cyclone, that has been observed since at least 1831, to see just what is driving it.

More about Jupiter – king of the planets

Juno mission website

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By Paul Sutherland

Paul Sutherland has been a professional journalist for nearly 40 years. He writes regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy, plus he has authored three books on astronomy and contributed to others.

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