Dear friends of Science and Astronomy, Venus probe returns first images @
http://news.bbc.co.uk/1/hi/sci/tech/4907866.stm

The Virtis image shows a "vortex" over the south pole

Mariner 10 took this image of the north polar vortex in the 1970s

Europe's Venus Express probe has returned its first images since slipping into
orbit around our nearest planetary neighbour on Tuesday.
They show the hothouse planet's south pole from a distance of 206,452km. Mission
scientists are already intrigued by a dark "vortex" feature which can be clearly
seen in one image. Venus Express will orbit the planet for about 500 Earth days
to study its atmosphere, which is thought to have undergone runaway greenhouse
warming. Venus' dense, largely carbon dioxide, atmosphere acts as a blanket,
trapping incoming solar radiation to heat the surface to an average temperature
of 467C (872F) - hot enough to melt lead.
Polar vortex
Experts had previously suspected the south pole might have a vortex feature; a
vast vortex with an unusual double-eye feature has already been observed over
the planet's north pole. But the south polar region has scarcely been observed.
"We can see there is a twister here that is similar to that which we know from
the north pole," said mission scientist Horst Uwe Keller. Venus Express science
team members say they want to know how these vortices remain stable and where
they get their energy from. European Space Agency (Esa) officials said the
pictures were "surprisingly clear", with "unexpected detail".
They were captured on 12 April by the Virtis (Visible and Infrared Thermal
Imaging Spectrometer) and Venus Monitoring Camera (VMC) instruments onboard, as
the spacecraft passed below the planet in an elliptical arc. The false-colour
Virtis composite image shows Venus' day side at left and night side at right,
and corresponds to a scale of 50km per pixel.
Night half
The spectacular night half was taken via an infrared filter and shows dynamic
spiral cloud structures in the lower atmosphere, around 55km in altitude. The
darker regions correspond to thicker cloud cover, while the brighter regions
correspond to thinner clouds. The smaller VMC image shows Venus at a scale of
150km per pixel and is also shown in false colour. It was imaged in the
ultraviolet part of the spectrum. Venus Express successfully executed a
50-minute main engine burn on Tuesday designed to slow its speed enough to be
captured by the planet's gravitational pull. As the spacecraft tightens its
orbit in the coming months, scientists expect it to capture more detailed and
revealing images of the planet. Scientists hope to learn how Venus, which is
similar to Earth in size, mass and composition, evolved so differently over the
last 4.6 billion years.
The mission is the first to be sent to the planet in 15 years.

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