The restless atmosphere of Venus (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 28 Nov 2007 20:45:10 GMT
ESA News
http://www.esa.int
28 November 2007
The restless atmosphere of Venus
Venus Express has studied the true extent of Venus' restless atmosphere.
This includes the planet's glow, its highly variable south polar vortex
and the dynamic upper atmosphere, different from what is seen on any other
rocky planet of the Solar System.
Venus' faint glow of light coming from molecules in the atmosphere is
providing scientists a detailed look into its physical and chemical
processes.
The first triumph for Venus Express was to uncover the planet's dramatic
south polar vortex in unprecedented, fine detail. The vortex powerfully
drives the cloud dynamics at all altitudes. "It plays an important role in
balancing the atmosphere," says Giuseppe Piccioni, VIRTIS co-Principal
Investigator at IASF-Istituto Nazionale di Astrofisica, Italy, who used
the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument
on Venus Express to discover and study the structure.
Planetary scientists believe that the double hurricane-like feature is
formed when warm air from the equatorial regions of Venus rises into the
atmosphere and travels down towards the pole of the planet. Once there, it
begins to cool and sink, spiralling down to create the vortex.
Venus Express has also revealed new details about the turbulent region
known as the 'sub-solar' region. This is the part of the planet that faces
the Sun, which changes slowly as Venus rotates. It is the area of Venus
that absorbs most of the incoming heat from the Sun, making it a crucial
location for the atmospheric dynamics.
As the heat streams into the atmosphere, the gas breaks up into rolling
pockets known as convection cells. "It is as if the whole region is
boiling," says Wojtech Markiewicz, VMC Principal Investigator at the
Max-Planck-Institute for Solar System Research, Germany, drawing an
analogy to the way milk boils in a pan.
Previous observations had hinted that the convection cells might be as
large as 200 km across, but this was difficult to explain using
conventional atmospheric physics. Venus Express observations clearly show
that the cells are much smaller, about 2030 km. At this size, the cells
are probably confined to the mid-atmosphere, leaving a stable atmospheric
layer below.
Venus has a high-altitude haze layer composed of brightly reflecting
aerosol particles and a new mystery has been revealed. On 13 January 2007,
under the gaze of Venus Express's instruments, two thirds of the planet's
southern hemisphere suddenly brightened as something triggered the
aerosols to form at a furious rate. As yet, no one knows what started this
amazing transformation. The feature disappeared just as quickly a few days
later when the aerosols had coagulated and the haze had cleared up.
Venus Express has also seen the glow from molecules of oxygen and carbon
dioxide in the atmosphere of the planet. In the case of carbon dioxide,
the 'airglow' is produced when the molecule absorbs and then re-emits a
photon from the Sun. This happens quite quickly and the glow from carbon
dioxide is confined to the day-side and low-pressure altitudes of the
planet.
In contrast, the faint glow from oxygen has been detected from night side
of the planet. This indicates a different mechanism at play. Indeed, the
oxygen glows when two stray oxygen atoms join together, releasing some
energy. Both types of emission tell scientists about the conditions in the
atmosphere.
"The airglow allows us to constrain models of the atmosphere," says Pierre
Drossart, Observatoire de Paris, France, and the VIRTIS co-Principal
Investigator. Already, the Venus Express results have allowed planetary
scientists to adjust the temperatures in the atmosphere in their computer
models to more realistic values.
Most importantly, Venus Express is monitoring changes in the airglow that
occur across the planet and at different times. This is providing
planetary scientists with an unprecedented level of detail and, as
Drossart says, "Science is made of the details."
Venus Express is certainly providing them.
Notes for editors:
The findings will appear in 29 November issue of the scientific journal
Nature, in the following papers:
'A dynamic upper atmosphere of Venus as revealed by VIRTIS on Venus
Express', by P.Drossart et al.
'South-polar features on Venus similar to those near the north pole', by
G.Piccioni et al.
'Morphology and dynamics of the upper cloud layer of Venus', by
W.Markiewickz et al.
Findings related to the study of the upper atmosphere will appear in the
article:
'The distribution of the 02 infrared nightglow observed with VIRTIS on
board Venus Exppress', by J-C. Gérard et al., accepted for publication in
the Geophysical Research Letters.
For more information:
Giuseppe Piccioni, VIRTIS co-Principal Investigator
IASF-Istituto Nazionale di Astrofisica, Italy
Email: giuseppe.piccioni @ iasf-roma.inaf.it
Pierre Drossart, VIRTIS co-Principal Investigator
Observatoire de Paris, France
Email : pierre.drossart @ obspm.fr
Wojtech Markiewicz, VMC Principal Investigator
Max-Planck-Institute for Solar System Research, Germany
Email: markiewicz @ mps.mpg.de
Håkan Svedhem, ESA's Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int
[NOTE: Images supporting this release are available at
http://www.esa.int/SPECIALS/Venus_Express/SEM2F373R8F_1.html ]
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