NASA’s Juno space probe has swooped low over Jupiter’s most famous feature, the Great Red Spot, to get the closest-ever views of a raging storm that is bigger than the Earth.
The spacecraft began its close encounter on Monday (July 10), flying as low as 3,500 km (2,200 miles) over the giant planet’s cloud tops. By the time it was above the Great Red Spot, it had climbed to a height of 9,000 km (5,600 miles).
The elongated orbit is designed to protect Juno’s instruments from Jupiter’s powerful radiation.
Pictures taken by the JunoCam onboard imager were radioed home on Tuesday. Space scientists were delighted by the detail in the huge spot, describing it as a tangle of dark, veinous clouds weaving their way through a massive crimson oval”.
The Great Red Spot has been shrinking over recent decades and its intensity changes. It is currently 16,350 km wide (10,160 miles) which is about 1.3 times the diameter of the Earth, but was twice the size a century ago.
Some books and websites incorrectly state that the spot – a powerful anti-cyclone in Jupiter’s clouds – has been around for more than 350 years. In fact, the current spot was first recorded by astronomers in 1831, though it might be a resurgence of a similar feature noticed by the famous observer Cassini in 1665.
Juno’s principal investigator, Scott Bolton, said: “For hundreds of years scientists have been observing, wondering and theorizing about Jupiter’s Great Red Spot. Now we have the best pictures ever of this iconic storm.”
He added: “It will take us some time to analyze all the data from not only JunoCam, but Juno’s eight science instruments, to shed some new light on the past, present and future of the Great Red Spot.”
Citizen scientists were quick to help process the raw images sent home by Juno, to turn them into visually pleasing pictures, with their detail enhanced.
One of them was Jason Major, a JunoCam citizen scientist and a graphic designer from Warwick, Rhode Island, USA. He told NASA’s Jet Propulsion Laboratory: “I have been following the Juno mission since it launched. It is always exciting to see these new raw images of Jupiter as they arrive. But it is even more thrilling to take the raw images and turn them into something that people can appreciate. That is what I live for.”
You can see more JunoCam images, including some processed by citizen scientists, at this NASA website.
The Juno mission
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 low 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.
Juno’s sensitive electronics are 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.
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.