Juno completes historic flyby over Jupiter’s Great Red Spot
NASA’s Juno spacecraft successfully completed the first-ever close flyby of the mysterious storm on Jupiter known as the Great Red Spot, and early images of the phenomenon are already being returned to Earth.
At 9:55 p.m. EDT (6:55 p.m. PDT) on Monday, July 10, only 11 minutes and 33 seconds after reaching perijove, the closest point to Jupiter in its current orbit, the spacecraft flew directly above the 10,000-mile- (16,000-km-) storm at an altitude of 5,600 miles (9,000 km), traveling at approximately 130,000 miles per hour.
All nine of Juno’s science instruments, including the JunoCam camera, operated successfully during the flyby.
Jupiter’s Great Red Spot has been observed for at least 350 years, with some sightings reported as early as the 1600s. It is the most powerful storm in the solar system, an anti-cyclone with winds up to 400 miles per hour (644 km/h).
Other missions to Jupiter, including NASA’s two Voyager spacecraft in 1979, the Galileo orbiter in the 1990s, and even Cassini on its way to Saturn approached the Great Red Spot and photographed it, but none from a vantage point as close as Juno’s.
This marks the first time a spacecraft has actually flown into the Great Red Spot’s cloud tops.
Juno entered orbit around Jupiter in July 2016. The recent flyby occurred during its sixth science orbit around the giant planet. Each polar orbit takes 53 days.
“For hundreds of years scientists have been observing, wondering and theorizing about Jupiter’s Great Red Spot,” said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. “Now we have the best pictures ever of this iconic storm. It will take us some time to analyze all the data from not only JunoCam, but [also from] Juno’s eight science instruments, to shed some new light on the past, present and future of the Great Red Spot.”
Juno was launched in August 2011 with the goals of looking beneath Jupiter’s cloud tops and imaging its auroras to collect data that will shed light on the planet’s formation, evolution, structure, magnetosphere, and atmosphere.
Data sent back by the spacecraft has already revealed the giant planet to be a turbulent world with polar auroras, a complex interior structure, and huge polar storms.
Scientists hope the flyover of the Great Red Spot will show the storm in unprecedented detail and help them answer questions that have puzzled many for decades and even centuries.
Candy Hansen of NASA’s Planetary Science Institute noted that three images, each from a different perspective, were taken during the flyby. One image captured the storm’s northern edge; a second was taken directly above its center, and a third, conducted with a methane filter, observed it from the south.
NASA initially reported that the earliest images from the flyby would not be available until Thursday, July 13, or Friday, July 14; however, the first raw, unprocessed images were put on JunoCam’s website on Wednesday, July 12. The photos will need more processing for details to become visible.
Many questions remain regarding the Great Red Spot, which scientists hope the images and other data collected by Juno will answer. However, “citizen scientists” have already begun working on some of the imagery that the spacecraft has produced.
“I have been following the Juno mission since it launched,” said Jason Major, a JunoCam citizen scientist and a graphic designer from Warwick, Rhode Island. “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.”
Capable of detecting radiation emanating from six different levels of clouds, Juno’s microwave radiometer should inform scientists about activity occurring up to 340 miles (547 kilometers) beneath the cloud tops.
Even after observing it with both ground-based telescopes and space probes, researchers still do not know the source of the storm’s power, how deeply it extends beyond the planet’s cloud tops, what makes it red, and how long it has been active.
They also do not understand why the Great Red Spot, which has a diameter larger than that of Earth, has been shrinking in recent decades and changing shape from round to oval.
Photos taken at various distances from the Great Red Spot will be returned before closeups. Juno has already confirmed activity is taking place as deep as 31 miles (50 kilometers) below Jupiter’s cloud tops, where no sunlight penetrates.
“These highly anticipated images of Jupiter’s Great Red Spot are the ‘perfect storm’ of art and science. With data from [the two] Voyager [probes], Galileo, New Horizons, Hubble and now Juno, we have a better understanding of the composition and evolution of this iconic feature,” said Jim Green, NASA’s director of planetary science. “We are pleased to share the beauty and excitement of space science with everyone.”
In upcoming flybys, Juno will map out the Great Red Spot’s gravitational field; search for possible mass below the cloud tops that could be influencing the storm, and look for signs of water clouds, ammonia ice, and lightning beneath the cloud tops.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.