Great Red Spot
Jupiter's Great Red Spot is pictured in this handout photograph taken by NASA's Voyager. The Great Red Spot is a massive anticyclone -- a storm three and a half times the size of Earth -- located in Jupiter?s southern hemisphere.Reuters

Gas giant Jupiter's iconic Great Red Spot is shrinking slowly, and a new study has revealed that the great storm will fade away within the next two decades.

The Great Red Spot has been observed since the 1600s. Located in Jupiter's southern hemisphere, it was first measured in 1800 and found to be four times bigger than Earth at the time.

When the Voyager 2 space probe flew past the storm in 1979, the size of the storm was found to be twice the size of Earth.

But the latest examination of the storm, which was carried out by NASA's $1-billion Juno probe, brought to light that it is just 30 percent bigger than Earth now, which means the storm is shrinking slowly and will turn into a memory within the next two decades.

Juno took stunning and detailed images of the storm during its flyby in July 2017. The craft will approach the gas-giant planet again in April 2018 and then in September 2019, but its view will not be as detailed as it was during its July 2017 flyby.

"In truth, the Great Red Spot has been shrinking for a long time. Now it's something like 13 degrees wide in longitude and only 1.3 times the size of the Earth. Nothing lasts forever. The Great Red Spot will in a decade or two become the Great Red Circle. Maybe sometime after that the Great Red Memory," Glenn Orton, a lead Juno mission team member and planetary scientist at NASA JPL, was quoted as saying by Business Insider.

So far the longest storm that Earth has experienced occurred in 1991 when Hurricane John had lasted for a span of 31 days. Earth doesn't have storms that last for hundreds of years like the gas giant Jupiter.

Earth's small size, its moderate rotation rate and its dynamic atmosphere are some factors that shape our planet's jet streams in a way that can disrupt weather systems and vortexes before things get too uncontrollable.

"They don't, at least not all of them," Orton said in an email to Business Insider.

"Think of the GRS [Great Red Spot] as a spinning wheel that keeps on spinning because it's caught between two conveyor belts that are moving in opposite directions. The GRS is stable and long-lived, because it's 'wedged' between two jet streams that are moving in opposite directions," he said.