According to NASA, Jupiter’s Great Red Spot is shrinking. In fact, the Great Red Spot has shrunk to its smallest sizer ever measured. The space agency says the swirling anti-cyclonic storm is now about 10,250 miles across.

In the 1800s, the Great Red Spot was estimated to be as big as 25,500 miles on its long axis. NASA Voyager 1 and Voyager 2 flybys of Jupiter in 1979 determined it to be approximately 14,500 miles across. In 1995, Hubble determined that it had shrunk to 13,020 on its long axis. In 2009, it was measured at 11,130 miles across.

According to the University of Tennessee at Knoxville’s Department of Physics and Astronomy, the anti-cyclonic storm is like a hurricane on Earth, but it is huge. Amazingly, three Earths would fit within its boundaries. This storm has also lasted for at least the 400 years that humans have watched it through telescopes.

Starting in 2012, scientists noticed a significant increase in the rate at which the spot is shrinking. The faster rate — 580 miles per year — is altering its shape from an oval to a circle.

“In our new observations it is apparent very small eddies are feeding into the storm,” noted Amy Simon of NASA’s Goddard Space Flight Center. “We hypothesized these may be responsible for the accelerated change by altering the internal dynamics and energy of the Great Red Spot.”

The astronomers plan to examine the movements of the tiny eddies and the internal dynamics of the Great Red Spot to conclude whether these eddies can fuel or sap momentum entering the upwelling vortex, explaining this mysterious shrinkage.