New imagery released from NASA’s Hubble Space Telescope reveals that Jupiter’s iconic Great Red Spot has been continuously decreasing in size.
The Great Red Spot is a monstrous anti-cyclonic circulation in the planet’s southern hemisphere that’s nearly three times larger in diameter than Earth itself. NASA estimates that the winds within the vortex are sustained at 340 mph, and as massive as the circulation is, NASA has noted that in the past year its diameter has decreased by 150 miles, or approximately 1.5 percent.
The circulation is still huge — over 10,000 miles in diameter — but observations of the gas giant have noted a continuous decline in its size in prior years as well. In a report made in May 2014, NASA noted that in 1979, the Great Red Spot was measured at 14,500 miles across. By 1995, it had decreased in size to 13,020 miles. In 2009, its diameter had decreased once again, down to 11,130 miles. In 2012, researchers believed the rate of shrinking had increased, noting a rate as high as 580 miles in diameter lost per year.
USA Today asked NASA planetary scientist Amy Simon if the spot could eventually disappear altogether. In short, the answer was “probably not.” She explained that the shrinking will most likely continue, but at some point it will probably stabilize.
The most likely case is that it will stabilize at a smaller size than it is now. (…) It could reach that point in the next decade. It has been there since at least the late 1870s and was much bigger then.
In addition to its reduction in size, the Great Red Spot has also been changing in appearance in other ways. The Hubble images have shown more of an orange hue to the vortex than red, and researches note that over the years it has shifted to a circular shape from an oval.
Even if it doesn’t disappear altogether, the Great Red Spot’s evolution into an aesthetically different feature may lead to the need for it to be renamed.
EarthSky reports that in addition to the visual changes of the spot, scientists have also identified a new feature on the planet that they describe as a wave. NASA’s Glenn Orton commented on the wave, stating that it had been identified decades prior by the Voyager 2, but it was difficult to make out. Scientists thought it might be a “fluke.” The wave, however, is a very real thing, and is believed to be much like baroclinic waves on Earth which are typically found near the formation grounds of cyclones up in Earth’s atmosphere.
“Until now, we thought the wave seen by Voyager 2 might have been a fluke,” Orton said. “As it turns out, it’s just rare!”