Astronomers around the world are digesting the news that Jupiter's atmosphere contains almost no water, and less helium than expected. They may now have to rethink theories on how the planets formed.
The information, just released by Nasa, the US space agency, came from the Galileo space probe, which travelled to the planet's outer atmosphere and dropped a smaller probe into it last month. The data has taken until now to be sent back.
The probe found that the expected cloud structure - three layers of ammonia, ammonium hydrosulphide, and water and ice - was not there. The absence of water and lightning puzzled researchers. They were also surprised by the low levels of helium, oxygen and neon.
The density, temperature and wind speeds of the atmosphere were all higher than expected, which has left astro- nomers uncertain about the creation of planets. Richard Young, of Nasa's Ames Research Center, said: "We are left to wonder, 'Where is the oxygen? Where is the water?' "
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