Using imagery from NASA’s Juno spacecraft, animators created this visualization of a flight into Jupiter’s Great Red Spot. The video begins about 2,000 miles (3,000 km) above the cloud tops of the planet’s southern hemisphere.
Every school kid knows Jupiter has a big red spot. Called the Great Red Spot, it’s a titanic oval storm 1.3 times the size of the Earth and big enough to see in a 6-inch telescope. Data collected by NASA’s Juno spacecraft during its first pass over Jupiter’s Great Red Spot in July 2017 indicate that this iconic feature penetrates well below the clouds.
“One of the most basic questions about Jupiter’s Great Red Spot is: how deep are the roots?” said Scott Bolton, Juno’s principal investigator, in a press release. “Juno data indicate that the solar system’s most famous storm has roots that penetrate about 200 miles (300 km) into the planet’s atmosphere.”
Regular cameras and telescopes can’t peer through clouds, but microwaves can. They’re also pretty good at heating a cup of tea. Juno carries something called a microwave radiometer that can detect what’s going on hundreds of miles below Jupiter’s cloud tops. With it, scientists are finally getting to the bottom of the Great Red Spot.
“Juno found that the Great Red Spot’s roots go 50 to 100 times deeper than Earth’s oceans and are warmer at the base than they are at the top,” said Andy Ingersoll, professor of planetary science at Caltech and a Juno co-investigator.
The difference in temperature between the hot bottom and cold top drives powerful winds that whirl clouds around the Spot’s outer edge at between 270 and 425 miles per hour (430-680 kph). Way stronger than a Category 5 hurricane. But like a hurricane the center of the GRS is relatively calm.
The future of the Great Red Spot is still up for debate. While the storm has been known for more than 300 years and monitored closely since 1830, it’s been shrinking of late. In the 19th century, the Great Red Spot was well over two Earths wide. Even at the time NASA’s Voyagers 1 and 2 sped by Jupiter on their way to Saturn and beyond, in 1979, the Great Red Spot was twice Earth’s diameter. Today, measurements by Earth-based telescopes indicate the oval that Juno flew over has diminished in width by one-third and height by one-eighth since Voyager times.
To date, Juno has completed eight science passes over Jupiter. Juno’s ninth science pass will be on Dec. 16.