One of the most iconic features of Jupiter is its iconic Great Red Spot. This feature is a massive storm that has lasted for centuries. Observations with the Hubble Space Telescope have shown that wind speeds increased in this massive storm.

Observations have confirmed that the wind speed increased by up to eight percent between 2009 and 2020 in the high-speed ring of the storm. The wind speeds in the innermost area of ​​the storm are significantly lower than in the outer area. Astronomers know that the Great Red Spot rotates counterclockwise at wind speeds of over 640 kilometers per hour.

While the Great Red Spot looks small considering how massive Jupiter is, the storm is bigger than Earth. Humans have been watching the storm for 150 years. The wind speeds measured by Hubble show a decrease of less than 2.5 kilometers per hour per earth year. Scientists say the change is so small that it would have been overlooked had it not been for more than a decade of data from Hubble.

With the power and resolution of Hubble, scientists can observe components of the storm up to a diameter of 170 kilometers. Scientists use software to track thousands and thousands of wind vectors for each observation of Jupiter. The project researchers admit that it is uncertain what the increased wind speed means.

Scientists want to know what is driving the storm and why it has lasted so long. We know that the Great Red Spot is a surge of material from within the planet. Scientists believe it has a structure like a tiered wedding cake with tall clouds in the middle flowing down the outer layers. Interestingly, the storm is shrinking and becoming more circular, as is evident from over a century of observations.

Ref: https://www.slashgear.com