Astronomers have produced the first detailed weather-map of the biggest and longest-running storm in the solar system. They used the world’s biggest telescopes to peer into a famous feature on giant gas-ball planet Jupiter called the Great Red Spot.

The 25,000-mile wide spot, which is three times the width of the Earth, has been raging for centuries and is prominent enough to be seen in stargazers’ backyard telescopes.

New results from an international team using two telescopes in Chile and two in Hawaii show thermal images of the swirling mass of cloud in as fine detail as the Hubble space telescope achives in visible light. (Hubble itself looked at Jupiter last year to study a bruise left in the clouds by a likely asteroid or comet impact).

They found that the reddest part of the Great Red Spot marks a slightly warmer heart of an otherwise distinctly chilly storm system with an average temperature of -163 C. This temperature difference sends the centre turning clockwise, although the rest of the spot is swirling in the opposite direction. Dark lanes at the edge of the storm are where gases descend into deeper regions of Jupiter’s atmosphere.

Oxford University scientist Leigh Fletcher said: “This is the first time we can say that there’s an intimate link between environmental conditions – temperature, winds, pressure and composition – and the actual colour of the Great Red Spot.”

Dr Fletcher, lead author of a report in journal Icarus, added: “Although we can speculate, we still don’t know for sure which chemicals or processes are causing that deep red colour. But we do know now that it is related to changes in the environmental conditions right in the heart of the storm.”

Colleague Glenn Orton, of NASA’s Jet Propulsion Laboratory in California, said: “This is our first detailed look inside the biggest storm of the solar system. We once thought the Great Red Spot was a plain old oval without much structure, but these new results show that it is, in fact, extremely complicated.”

Telescopes used in the study were the European Southern Observatory’s Very Large Telescope (VLT) in Chile, the Gemini Observatory telescope in Chile, the National Astronomical Observatory of Japan’s Subaru telescope in Hawaii and the NASA Infrared Telescope Facility in Hawaii.

Picture: The photos show a thermal image of the Great Red Spot and its surroundings taken using the VLT in Chile on 18 May 2008 and a visible-light image from Hubble three days previously. (Credit: ESO/NASA/JPL/ESA/L. Fletcher).

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