Double vortex at Venus South Pole unveiled! (Forwarded)

ESA News
http://www.esa.int

27 June 2006

Double vortex at Venus South Pole unveiled!

ESA's Venus Express data undoubtedly confirm for the first time the
presence of a huge 'double-eye' atmospheric vortex at the planet's south
pole. This striking result comes from analysis of the data gathered by the
spacecraft during the first orbit around the planet.

On 11 April this year, Venus Express was captured into a first elongated
orbit around Venus, which lasted 9 days, and ranged between 350 000 and
400 kilometres from Venus' surface. This orbit represented for the Venus
Express scientists a unique opportunity to observe the planet from large
distances. This made it possible to obtain first clues about the Venusian
atmospheric dynamics on a global scale, before the spacecraft got closer
and started observing the planet in greater detail.

During this first orbit -- called the 'capture orbit' -- some of the Venus
Express instruments were used to perform the first observations at
different distances from Venus, for a few hours per time on six different
slots between 12 and 19 April 2006.

Amazing infrared, visible and ultraviolet images of the Venusian globe
already reveal several atmospheric features of great interest. The most
striking of these is a huge, double-eye atmospheric vortex over the south
pole, not dissimilar from the equivalent structure present at the north
pole -- the only one previously studied in some detail.

Only glimpses of the stormy atmospheric behaviour at the south pole were
obtained by previous missions (Pioneer Venus and Mariner 10), but such a
double-eye structure was never clearly seen before now.

High velocity winds are known to spin westwards around the planet, and to
take only four days to complete a rotation. This 'super-rotation',
combined with the natural recycling of hot air in the atmosphere, would
induce the formation of a vortex structure over each pole. But why two
vortexes?

"We still know very little about the mechanisms by which the
super-rotation and the polar vortexes are linked," said Håkan Svedhem,
ESA's Venus Express Project Scientist. "Also, we are still not able to
explain why the global atmospheric circulation of the planet results in a
double and not single vortex formation at the poles. However the mission
is just at the beginning and it's doing fine; we expect this and many
other long-standing mysteries to be addressed and possibly solved by Venus
Express," he added. Atmospheric vortexes are very complex structures that
are very difficult to model, even on Earth.

Thanks to these first pictures, it has also been possible to observe the
presence of a collar of cold air around the vortex structure, possibly due
to the recycling of cold air downwards.

Views of the southern hemisphere of Venus in visible and ultraviolet light
show interesting atmospheric stripe-like structures. Spotted for the first
time by Mariner 10 in the 1970s, they may be due to the presence of dust
and aerosols in the atmosphere, but their true nature is still
unexplained. "Venus Express has the tools to investigate these structures
in detail," added Svedhem. "Studies have already begun to dig into the
properties of the complex wind fields on Venus, to understand the
atmospheric dynamics on local and global scales."

Venus Express also made use for the first time ever from orbit of the
so-called 'infrared windows' present in the atmosphere of Venus -- if
observed at certain wavelengths, it is possible to detect thermal
radiation leaking from the deepest atmospheric layers, revealing what lies
beneath the dense cloud curtain situated at about 60 kilometres altitude.

The first infrared images making use of the 'windows' show complex cloud
structures, all revealed by the thermal radiation coming up from different
atmospheric depths. In the colour scheme shown in the image at right, the
brighter the colour (that is, the more radiation comes up from the lower
layers), the less cloudy is the observed area.

During capture orbit, preliminary data about the chemical composition of
the atmosphere were also retrieved. Venus' atmosphere is mainly composed
of carbon dioxide (CO2). The incoming solar radiation dissociates this
molecule into carbon monoxide (CO) and oxygen in the upper atmospheric
layers. In fact, Venus Express has already spotted the presence of an
oxygen (O2) airglow high in the atmosphere. However, Venus Express has
revealed the presence of carbon monoxide as low as the cloud-layer top.

Scientists will continue the data analysis and retrieval to understand the
phenomenon, which is very important to clarify the complex chemical
processes and cycles at work in the atmosphere of Venus under the
influence of solar radiation.

Since 7 May 2006 Venus Express has been circling the planet in its final
24-hour orbit, ranging between 66 000 and 250 kilometres from Venus --
therefore at much closer distances with respect to the capture orbit.
Venus Express scientists are now analysing the new data coming in, which
already show what seems to be exciting new features. "We have never seen
Venus in such great detail so far. We are eagerly waiting for these new
data to be available," concluded Svedhem.

Note to editors:

On 28 June 2006, from 10:00 to 12:00, Venus Express scientists gathering
at ESA's Space Operations Centre (ESOC) in Darmstadt, Germany, will be
available for real-time phone interviews. Interested media are invited to
call the following numbers for the interview set-up:

ESOC Communication Office
+49 61 5190 2266
+49 61 5190 2861

For more information:

Håkan Svedhem, ESA Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int

[NOTE: Images supporting this release are available at
http://www.esa.int/esaCP/SEMYGQEFWOE_index_1.html ]

Feature

* ESA astronaut C. Nicollier on voyaging to Venus
mms://esamultimedia.esa.int/multimedia/audio/cn_venus.mp3
* VOI highlights and press conference
http://www.esa.int/SPECIALS/Venus_Ex...RONFGLE_0.html
* ESApod: Venus Express
http://www.esa.int/SPECIALS/Venus_Ex...XANFGLE_0.html

VOI updates

* Venus Express' initial orbit matches expectations
http://www.esa.int/SPECIALS/Venus_Ex...1SNFGLE_0.html
* Venus Express 'talks' to Earth
http://www.esa.int/esaCP/SEMZ7QNFGLE_index_0.html
* Venus Express main engine burn ended
http://www.esa.int/esaCP/SEMMYPNFGLE_index_0.html
* Venus Express reappears from behind Venus
http://www.esa.int/esaCP/SEMQPPNFGLE_index_0.html
* Pre-planned thrill -- Venus Express disappears behind Venus
http://www.esa.int/esaCP/SEMXKPNFGLE_index_0.html
* Venus Express main engine burn starts
http://www.esa.int/esaCP/SEM7CPNFGLE_index_0.html
* Venus Express slews and prepares to 'brake'
http://www.esa.int/esaSC/SEM77PNFGLE_index_0.html
* Venus Orbit Insertion timeline
http://www.esa.int/esaCP/SEMMM0NFGLE_index_0.html
* Looking at Venus
http://www.esa.int/SPECIALS/Venus_Express/index.html
* ESA's Venus Express to reach final destination
http://www.esa.int/esaCP/SEM0UGNFGLE_index_0.html

Related articles

* Venus Express has reached final orbit
http://www.esa.int/esaCP/SEM33O8ATME_index_0.html
* Unexpected detail in first-ever Venus south pole images
http://www.esa.int/esaSC/SEMUTYNFGLE_index_0.html
* Venus within ESA probe reach
http://www.esa.int/esaCP/SEME02NFGLE_index_0.html
* And now straight to Venus!
http://www.esa.int/esaSC/SEMIMWMVGJE_index_0.html
* Successful Venus Express main engine test
http://www.esa.int/esaCP/SEMVX5MVGJE_index_0.html
* First light for the Venus Monitoring Camera
http://www.esa.int/esaCP/SEMLWVULWFE_index_0.html
* Venus Express performs flawlessly, LEOP complete
http://www.esa.int/esaCP/SEMK9UJBWFE_index_0.html
* Venus Express mission operations update
http://www.esa.int/SPECIALS/ESOC/SEM780738FE_0.html
* Venus Express en route to probe the planet's hidden mysteries
http://www.esa.int/esaCP/SEM56Q638FE_index_0.html

Related links

* ESA Mission Operations

http://www.esa.int/spacecraftops/ESO...551445449.html
* Webcam from ESOC
http://www.esa.int/esaCP/SEMN3Y274OD_index_0.html