IT WAS large even by Earth standards鈥攁nd monstrous for Mars. Earlier
this month, the Hubble Space Telescope got a snapshot of a Martian 鈥渉urricane鈥�
three times bigger than anything yet seen.
鈥淚t鈥檚 a giant cyclonic storm that looks very much like a hurricane,鈥� says Jim
Bell, an astronomer at Cornell University in Ithaca, New York. 鈥淚t鈥檚 swirling
around with a big eye, 200 miles in diameter.鈥� The storm, made up of clouds of
water ice, is over 1700 kilometres (1050 miles) across. 鈥淓ven on the scale of
Earth storms, it鈥檚 a big one,鈥� says Bell.
The hurricane probably formed as frozen carbon dioxide at the north pole
transformed into vapour during the Martian summer, leaving water ice behind.
Then the temperature difference between the bright, cold icecap and the warm,
dark sand whipped up a high wind.
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鈥淭he size of this suggests there could be fairly intense winds,鈥� says Peter
Gierasch, also at Cornell. But NASA鈥檚 Mars Global Surveyor had a broken antenna
and couldn鈥檛 collect details about the storm, such as how thick the clouds were.