There's a relatively warm heart beating at the center of Jupiter's icy cyclone. The first-ever detailed thermal images of the planet's Great Red Spot, released yesterday, reveal part of the dynamo that drives the 35,000-kilometer-wide storm. Astronomers using large telescopes in Chile and Hawaii have found that the brightest orange-red zone in the central part of the spot runs up to 4°C warmer than the rest of the storm. Its average surface temperature is about -160°C, but that small difference apparently has been enough to keep the spot swirling, just as air-temperature differences on Earth can generate cyclonic storms. Astronomers still don't know why the Great Red Spot is red, but they suspect that the same forces creating the heat wave in the center of the storm are responsible.