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Why is Jupiter’s Great Red Spot shrinking?

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photo of Jupiter taken by Voyager 1 — Jupiter Photograph of Jupiter taken by Voyager 1 on February 1, 1979, at a range of 32.7 million km (20.3 million miles). Prominent are the planet's pastel-shaded cloud bands and Great Red Spot (lower centre).

The Great Red Spot on Jupiter has been observed shrinking since the late 19th century, when its length was approximately 48,000 km (30,000 miles). While the feature is a long-lived anticyclonic storm system, scientists have not yet developed an exact theory to explain its specific energy source or the precise mechanisms driving its long-term stability and current reduction in size.12

Since 2012, the spot has become more circular and has been shrinking at an accelerated rate of about 900 km (580 miles) per year. Although researchers have observed the storm interacting with smaller eddies and high-speed currents, and have hypothesized that it may be powered by the condensation of water or ammonia at lower atmospheric levels, the specific reasons for its ongoing contraction remain a subject of active study.12