The Great Red Spot was thought to be a storm shaped as a flat “pancake,” according to Scott Bolton, principal investigator of NASA’s Juno mission and director of the space science and engineering division at the Southwest Research Institute in San Antonio.
“We knew it lasted a long time, but we didn’t know how deep or how it really worked,” Bolton said in the press conference.
In February and July 2019, NASA’s Juno spacecraft flew directly over the Great Red Spot, which is about 10,000 miles (16,000 kilometers) wide, to figure out how deep the vortex extends beneath the visible cloud tops. Two papers published Thursday in the journal Science have detailed what Juno discovered.
Scientists had believed the depth of the storm and the planet’s weather layer would be constrained to depths where sunlight can penetrate or water and ammonia are expected to condense — the planet’s cloud level. However, the storm wasn’t a shallow meteorological feature, the researchers found.
A microwave radiometer on Juno gave scientists a three-dimensional look at the planet. They discovered that the Great Red Spot is between 124 miles (200 kilometers) and 311 miles (500 kilometers) deep, extending much deeper into the gas giant than expected.
“The Great Red Spot is as deep within Jupiter as the International Space Station is high above our heads,” said Marzia Parisi, research scientist at the NASA Jet Propulsion Laboratory in Pasadena, California.
The Great Red Spot is deeply rooted, but the team found it’s still shallower than the zonal jets that power the storm, which extend to depths approaching 1,864 miles (3,000 kilometers).
While the storm rages on, the size of the spot is shrinking. In 1979, it was twice Earth’s diameter. Since then, the spot has shrunk by at least a third.
Resilient polar cyclones
Five years ago, scientists used data gathered by Juno to capture photos and learn more about Jupiter’s poles.
Juno found the gas giant has five cyclonic storms at the south pole in the shape of a pentagon and eight cyclonic storms at the north pole forming an octagon.
When Juno observed the cyclones five years later using the Jovian Infrared Auroral Mapper, it found the storms stayed in the same location.
The polar cyclones showed patterns of trying to move toward the poles, but the cyclones on top of each pole pushed back. This explains why the storms have remained in the same place.
Vertical patterns of wind circulation
Jupiter’s clouds are embedded in the east and west jet streams, which extends 200 miles (322 kilometers) deep, said Keren Duer, a doctoral student at the Weizmann Institute of Science in Israel.
When the research team followed the movement of ammonia, it revealed that it traveled in an up-and-down and north-south movement surrounding the jet streams, she said.
Those circulation cells in both of Jupiter’s hemispheres share similar characteristics to Earth’s Ferrel cells, which are the wind circulation patterns in the mid-latitudes of the Northern and Southern hemispheres. Those cells have a large influence on our planet’s climate, Duer said.
Jupiter contains eight Ferrel cells in each hemisphere compared to Earth, which has only one per hemisphere, she said. Earth’s cells extend 6 miles from the surface compared to Jupiter’s cells, which start at the cloud level and extend at least 200 miles, she added.
“This means that the cells on Jupiter are at least 30 times deeper than the equivalent cells on Earth,” Duer said.
Since 2016, the Juno spacecraft — as wide as a basketball court — has circled Jupiter, scanning the atmosphere and mapping its magnetic and gravitational fields.
In January, NASA announced it would be extending Juno’s mission through September 2025.
Astronomers have been monitoring the Great Red Spot since 1830.