Over the last decade, Jupiter's Great Red Spot has contracted from an oval into sort-of circle. ( NASA/ESA/A.Simon)
Over the last decade, Jupiter's Great Red Spot has contracted from an oval into sort-of circle. ( NASA/ESA/A.Simon)

Jupiter’s Great Red Spot Is Shrinking

Anyone who’s seen a picture of Jupiter has stared — for more than a few seconds — at that giant, massive red splotch in the planet’s southern hemisphere. It’s the bloodshot eye of a violent storm bigger than Earth that’s been raging for centuries.

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The Great Red Spot in happier times, captured by Pioneer 11 in 1974. (NASA)

the Great Red Spot is the smallest it’s ever been

Amy Simon

That’s less than half of historical measurements.

In the 1800s, astronomers estimated the spot was about 25,000 miles wide. But since the 1930s, observations have suggested it’s getting smaller. Voyager 1 and 2 fly-bys in the late 1970s placed the squinty spot at just 14,500 miles across — or the equivalent of two Earths (Earth’s diameter measures 7,918 miles wide). But the splotch has gotten even smaller. In the photo above, the diameter measured in 1995 is around 13,000 miles. In 2009? Roughly 11,000 miles. And now, 10,250 miles. It appears as though the thing is losing about 580 miles per year, and that the rate of shrinkage may be speeding up. Scientists aren’t certain why the storm is shriveling up, or if it will disappear completely.

It’s not the first time Earthlings have witnessed a shifting storm on another planet. Jupiter has storms (and atmospheric bands) that come and go fairly regularly. Neptune has a Great Dark Spot. And recently, a huge storm erupted on Saturn and formed a massive white eye; the eye eventually bled into the atmosphere and wrapped around the planet, lasting for months before fading away.

A huge storm encircled Saturn in 2011. (>a href=”http://www.ciclops.org/view.php?id=6865″ target=” blank”>NASA/JPL-Caltech/Space Science Institute)