A restless
'hurricane eye' morphs and changes shape within days at the south pole of
Venus, according to observations from the Venus Express spacecraft.
The core of
the gigantic vortex glows brightly in thermal infrared, suggesting that
turbulent atmospheric gases are sinking downward and making the region hotter.
"Simply
put, the enormous vortex is similar to what you might see in your bathtub once
you have pulled out the plug" said Giuseppe Piccioni, a Venus Express scientist
in Rome, Italy.
The study
of this phenomenon first appeared in the November 2007 issue of the journal Nature.
Scientists released new images of the storm this week.
The
1,240-mile-wide vortex (2,000 km) can shift in 24 hours from an eye shape to an
hour-glass shape, and at other times appears oval. The whole structure
resembles a rapidly changing hurricane eye as seen on Earth, with some
differences.
"The
main difference is that the Venusian vortex is upside down with respect to the [Earth]
hurricane, meaning that the vertical air flow of the hurricane is down-top
[meaning air flows inward at the bottom of a storm and then up through the
storm] while the Venusian one is top-down," Piccioni told SPACE.com.
The Venus
vortex also differs from Earth hurricanes because of its monstrous planetary
scale, and it is probably permanent, according to Piccioni.
A mystery still
surrounds how the vortex formed in the first place. The atmospheric gases flow
dynamically in different directions and at different altitudes.
"One
explanation is that atmospheric gases heated by the Sun at the equator, rise
and then move poleward," said Colin Wilson, a Venus Express scientist at
the University of Oxford, Great Britain. "In the polar regions, they
converge and sink again. As the gases moves towards the poles, they are
deflected sideways because of the planet's rotation."
Scientists
have long observed Venus' wacky
weather features. The 'hurricane eye' was discovered in 1974 by the Mariner
10 spacecraft. A similar structure exists on the planet's north pole, which was
observed by the Pioneer Venus mission in 1979.
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