Puzzling 'Eye Of A Hurricane' On Venus
ScienceDaily (Mar. 17, 2008) — Venus Express has constantly been observing the south pole of Venus and has found it to be surprisingly fickle. An enormous structure with a central part that looks like the eye of a hurricane, morphs and changes shape within a matter of days, leaving scientists puzzled.
The eye of the hurricane is at the centre of a 2000 km-wide vortex. It was discovered in 1974 by the Mariner 10 spacecraft. There is a similar structure on the planet’s north pole, which was observed by the Pioneer Venus mission in 1979.
Venus Express scientists have been studying the structure in the thermal infrared, the wavelength range which reveals the temperature at the cloud-tops. Seen in this wavelength, the core of the vortex appears very bright, probably indicating that a lot of atmospheric gases are moving downward in the region, which creates a depression at the cloud-tops, 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” says Giuseppe Piccioni, co-Principal Investigator for the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express, at IASF-INAF, Rome, Italy.
In June 2006, the vortex appeared hourglass-shaped, closely matching observations in the north polar region by Pioneer Venus. Now we know that it changes its shape within a matter of days, from orbit to orbit. The image taken on 26 February 2007 shows the 'classic' dipole shape at the centre of the vortex, similar to that which has been observed previously. But an image taken a mere 24 hours earlier shows the centre of the vortex to be almost circular, indicating that the shape of this feature can change very fast. At other times, it is typically oval.
The vortex is very complex, with atmospheric gases flowing in different directions at different altitudes.
Scientists are not sure what actually creates the vortex. Colin Wilson, at the University of Oxford, says, “One explanation is that atmospheric gases heated by the Sun at the equator, rise and then move poleward. In the polar regions, they converge and sinks again. As the gases moves towards the poles, they are deflected sideways because of the planet’s rotation.”
The dynamic nature of this vortex is similar to behaviour observed in other vortices on Earth, including those observed at the centre of hurricanes.
Investigators will keep a close watch on the polar region and its variability, in order to gain a better understanding of how it works.
Adapted from materials provided by European Space Agency.Weather notes
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SHIP owners and harbour contractors have been warned by a maritime specialist that they face fines of up to R60000 or three years in jail if they do not stick to accident procedures covering employees injured on duty.
The alert has been issued by Tony Edwards, of Shepstone &0x0026; Wylie‘s International Transport, following the SA Maritime Safety Authority‘s (Samsa‘s) having circulated a special notice.
It was that ship owners, masters and shore contractors must report casualties, accidents and serious injuries to them in terms of Section 259 of the Merchant Shipping Act of 1951.
Edwards said that in terms of the Act a fine of up to R5000 or imprisonment not exceeding three months could be imposed for a failure to report an accident.
“Increased penalties apply to a failure to report loss of life or serious injury, in which case the punishment may be a fine of up to R 60000 or imprisonment not exceeding three years.”
The requirement to report accidents applies to both South African-flagged and foreign- flagged ships. “Where a South African-flagged ship is involved, the accident must be reported to Samsa irrespective of where it occurred.
“An event involving a foreign-flagged ship need only be reported to Samsa if it occurred during a voyage to a South African port or within its territorial waters, or within a local port.
An accident must be reported to Samsa within 24 hours of a ship‘s arrival in a South African port. If it occurred in a South African port, it must be reported before the ship sails.