A large red oval feature on Jupiter, 24,000 kilometres (15,000 miles) long and 11,000 kilometres (7,000 miles) wide. It was first reported by Robert Hooke in 1664 and has been observed ever since, during which time it has apparently varied to some extent in size and colour. The reason for its existence remains uncertain but it rotates like a giant anticyclone, with a westerly wind on its northern edge and an easterly wind to the south.
