The most recognizable storm in the solar system used to be so big that it could fit three whole Earths. Now, it has room for only one. Jupiter’s Great Red Spot is shrinking, and has been for decades.
The earliest observations of a massive, red spot on the face of Jupiter date back as far as the 1600s. Astronomers don’t know whether this spot was the Great Red Spot we know today, but it’s likely. Routine telescope observations of the oval-shaped storm, where winds can reach 400 miles an hour, began in the late 1870s. For the Great Red Spot, these were the “years of its glory,” according to John H. Rogers, who plotted the history of the storm’s dimensions in The Giant Planet Jupiter. Not long after, perhaps around 1920, astronomers noticed the storm was getting smaller. In 2012, amateur astronomers using backyard telescopes to observe Jupiter saw that the rate of shrinking had actually accelerated.