Jupiter’s Red Spot

The Not-So-Great Red Spot[1]

Almost everyone has heard of Jupiter’s giant red spot. It is easily viewed with amateur telescopes. The red spot joins Saturn’s rings and the Martian polar caps as “must-see” features for Solar System enthusiasts. But the GRS is an inconstant icon. In fact, in recent years observers have become increasingly alarmed about how small (relatively speaking) the spot has become. Visually it’s far less impressive than it was two or three decades ago.

Is it really shrinking and, if so, might it someday disappear completely? Yes, it really is shrinking. Who knows what its future will be.

We know it is a gigantic storm. Arguably no planetary feature in the Solar System is better known that Jupiter’s Giant Red Spot, shown above in a contrast-enhanced composite of Voyager images from 1979. Note the vast regions of disturbed cloud flow to its north and south, along with the Earth-size white oval gliding nearby.

Studies of the internal dynamics of the spot will help us to model its fate, so we continue to make yearly Hubble observations. Amateur observations are critical for monitoring the GRS. Regular reports help astronomers to fill in the gaps between studies with HST and professional telescopes.

All things considered, we expect that the Great Red Spot will continue to shrink for some time to come. We don’t expect it to disappear completely—but for now, what happens in the years ahead is anyone’s guess.

[1] See Amy A. Simon, “Jupiter’s Shrinking Storm: The Not-So-Great Red Spot,” Sky and Telescope (131, 3 March 2016), pp. 8-21. Also “Jupiter’s Great Red Spot Viewed by Voyager I,” at the NASA web site.


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