A 300-year-old tornado on the planet Jupiter, known to scientists as the “great red spot,” turns out to be much deeper than researchers used to think.

This is evident from research results published on Thursday by the American space agency NASA. Microwave and gravity measurements are taken by NASA’s Juno spacecraft now show that the large red spot is between 350 and 500 kilometres deep.

Scientists already knew that the spot is about 16,000 kilometres wide and about three times the size of the Earth. Jupiter itself is about a thousand times the size of Earth, making it the largest planet in our solar system.

The storm has likely been raging for at least 300 years and is raging across the planet’s southern hemisphere with winds of 430 kilometres per hour. The most powerful hurricanes on Earth measure wind speeds of around 250 kilometres per hour.

The stain may still be large, but it is getting smaller and smaller. In 1979, the Voyager spacecraft captured a picture of the storm from a distance of 9.2 million kilometres. Compared to recent photos of the stain, it is now a third smaller.

Juno has been studying Jupiter since 2016 and, in that time, flew past the planet 37 times at an altitude of more than 3,500 kilometres. In 2017, the vessel sent a picture of the large red spot for the first time.

Jupiter is also called a gas giant because the planet consists mainly of hydrogen and helium. The distance between the sun and Jupiter is on average 778 million kilometres; the closest the Earth comes to the planet is 588 million kilometres.