Storm on the planet Jupiter that moves in longitude but remains centred at about latitude 22° south.
A high-pressure centre, it is oval, measuring about 7,500 mi (12,000 km) north to south, roughly the diameter of Earth, and nearly twice as wide east to west. Its discovery in the 1660s is attributed to Gian Domenico Cassini or Robert Hooke . Its colour, whose cause is unknown, varies from brick-red to brownish; it tends to change colour over a period of years.