Jupiter's trademark Great Red Spot — a swirling storm feature larger than Earth — is shrinking. This downsizing, which is changing the shape of the spot from an oval into a circle, has been known about since the 1930s, but now these striking new NASA/ESA Hubble Space Telescope images capture the spot at a smaller size than ever before.

Jupiter's Great Red Spot is a churning anticyclonic storm . It shows up in images of the giant planet as a conspicuous deep red eye embedded in swirling layers of pale yellow, orange and white. Winds inside this Jovian storm rage at immense speeds, reaching several hundreds of kilometres per hour.

Historic observations as far back as the late 1800s gauged this turbulent spot to span about 41 000 kilometres at its widest point — wide enough to fit three Earths comfortably side by side. In 1979 and 1980 the NASA Voyager fly-bys measured the spot at a shrunken 23 335 kilometres across. Now, Hubble has spied this feature to be smaller than ever before.

"Recent Hubble Space Telescope observations confirm that the spot is now just under 16 500 kilometres across, the smallest diameter we've ever measured," said Amy Simon of NASA's Goddard Space Flight Center in Maryland, USA.

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