Re: The puzzling 'eye of a hurricane' on Venus (Forwarded)
- From: gb <gb6726@xxxxxxxxx>
- Date: Tue, 25 Mar 2008 07:38:26 -0700 (PDT)
On Mar 23, 10:55 pm, Andrew Yee <a...@xxxxxxxxxxxxxxxxxxxxxx> wrote:
ESA Newshttp://www.esa.int
13 March 2008
The puzzling 'eye of a hurricane' on Venus
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.
The fickle puzzle
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 dynamic nature of the vortex can be seen clearly in the video. It
shows that the vortex is very complex, with atmospheric gases flowing in
different directions at different altitudes.
What creates the puzzle?
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 sink again. As the gases move 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.
Notes for editors:
The discovery was reported in 'South-polar features on Venus similar to
those near the north pole' by G. Piccioni et al. published in Nature on 29
November 2007.
For more information:
Giuseppe Piccioni, VIRTIS co-Principal Investigator
IASF-INAF, Rome, Italy
Email: Giuseppe.Piccioni @ iasf-roma.inaf.it
Pierre Drossart, VIRTIS co-Principal Investigator
Observatoire de Paris, France
Email: Pierre.Drossart @ obspm.fr
Håkan Svedhem, ESA Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int
[NOTE: Images and weblinks supporting this release are available athttp://www.esa.int/esaCP/SEMIZFM5NDF_index_1.html]
Exchange of temperature. Saturn is an Earth diameter wider
as it rotates once every 10 hours. The region at the South
Pole is a few degrees warmer. Cold gas cloud tops pours in,
and heat rises at the same time. If there is a way for heat to
exchange, it happens. Obviously a large source of warm and
cold was able to connect through a vortex. One disturbance
can cause that like the plumetting of an object from space.
Since most of the substance is gasses, there is no surface
to stop vortex formation as long as heat can exchange in a
uniform structure, it goes.
.
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