Jupiter’s Great Red Spot seems to be on a cosmic diet, shrinking rapidly before our eyes. Jupiter’s Great Red Spot might be, quite literally, the perfect storm: It’s a swirling, anti-cyclonic vortex that’s big enough to engulf three Earths and has been raging in the atmosphere of the solar system’s largest planet for at least 400 years.
Jupiter’s Great Red Spot is a high-pressure anticyclone. This monster storm shows up in images as a conspicuous deep red eye embedded in swirling layers of pale yellow, orange and white. It rotates in an anti-clockwise direction in the planet’s southern hemisphere. Winds inside it rage at immense speeds, reaching several hundreds of km per hour.
The Great Red Spot itself may have been mentioned in writings before the late 1800s. There are references to Jupiter’s ‘permanent spot’ dating back as far as the late 1600s, although some astronomers disagree that the permanent spot mentioned is the Great Red Spot.
Historic observations gauged this turbulent spot to span about 41,000 km at its widest point – wide enough to fit three Earths comfortably side by side.
In 1979 and 1980, NASA’s Voyager fly-bys measured the Great Red Spot at a shrunken 23,335 km across.Recent Hubble Space Telescope images of the storm show that it is now 10,250 miles (16,496 kilometers) across, which is less than half the size of the storm in the late 1800s. At one point, scientists theorized that three Earths could fit inside the Great Red Spot, but today, only the width of one Earth could fit within the raging tempest.
As the spot diminishes, its shrinkage rate appears to be accelerating. Amateur observations from 2012 show the storm’s “waistline” is reducing by 580 miles (933 km) a year, a little less than the driving distance from New York City to Cincinnati.
Nobody knows for sure why the Great Red Spot is getting smaller.
“One possibility is that some unknown activity in the planet’s atmosphere may be draining energy and weakening the storm, causing it to shrink,” Hubble officials wrote in a statement.
“In our new observations, it is apparent that very small eddies are feeding into the storm,” Amy Simon, associate director for strategic science at NASA’s Goddard Space Flight Center, said in a statement. “We hypothesized that these may be responsible for the accelerated change, by altering the internal dynamics and energy of the Great Red Spot.”