New details on venusian clouds revealed (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 30 May 2008 14:56:43 GMT
ESA News
http://www.esa.int
30 May 2008
New details on venusian clouds revealed
As ESA's Venus Express orbits our sister planet, new images of the cloud
structure of one of the most enigmatic atmospheres of the Solar System
reveal brand-new details.
Venus is covered by a thick layer of clouds that extends between 45 and 70
km above the surface. These rapidly-moving clouds are mainly composed of
micron-sized droplets of sulphuric acid and other aerosols (fine solid or
liquid droplets suspended in a gas), the origin of which is unknown.
Earlier missions have shown that the clouds resemble Earth's light fogs,
but their thickness creates an impenetrable veil.
The Venus Monitoring Camera (VMC) on board Venus Express has been
observing the top of the cloud layer in visible, near-infrared and
ultraviolet wavelengths. Ultraviolet observations have shown a wealth of
new details including a variety of markings created by variable
concentrations of different aerosols located at the top of the cloud
layer.
The first image presented here (top of the article) is a global view of
the southern hemisphere of Venus, obtained from a distance of 30 000 km.
The south pole is at the bottom, while equator is at the top.
The appearance of the cloud veil changes dramatically from the equator to
the pole. At low latitudes, the shapes are spotty and fragmented. This is
indicative of vigorous, convective movement -- like that of boiling water
in a pot -- powered by the radiation of the sun heating the clouds and the
atmosphere itself. The bright lace visible on top of the darker cloud deck
is made of freshly formed droplets of sulphuric acid.
At mid latitudes, the scene changes -- convective patterns give way to
more streaky clouds indicating that convection is weaker here, as the
amount of sunlight absorbed by the atmosphere decreases.
At high latitudes, the cloud structure changes again. Here it appears as a
dense, almost featureless haze forming a kind of polar cap or 'hood' on
Venus. The dark, circular feature visible at the lower edge of the image
is one of the dark streaks usually present in the polar region, indicating
atmospheric parcels spiralling around and towards the pole.
Additional images provide close-up views of the structures described above
and show details never seen before. This is possible thanks to the
elongated orbit of Venus Express, which allows imaging of the same
phenomena from decreasing distances.
The second and third images zoom-in on the equatorial region, showing
details of the cloud top and of the bright lace of sulphuric acid, from 20
000 and 15 000 km respectively.
The fourth image from the top is a close-up on the transition region
between the equatorial regions dominated by convection and the
mid-latitudes populated by streaky clouds. This region is located at about
40-50 degrees latitude and was imaged from a distance of about 15 000 km.
The way the transition between structures and dynamics so different from
each other occurs, is one of the outstanding enigmas in our understanding
Venus.
The second-last image, obtained from a distance of about 20 000 km, is a
zoom-in on the south polar 'hood', located inside a 60-degree-latitude
circle. This region varies greatly on time scales of days.
In this particular case it is very bright and uniform and lacks
small-scale markings. However several global dark streaks visible here
usually cross the polar regions and seem to indicate strong 'jet' winds.
The last image, a mosaic composed of 40 single ultraviolet images, covers
latitudes from the equator (bottom) to the northern polar regions (top).
The transition from mottled clouds in low latitudes to streaky patterns at
mid-latitudes is quite similar to that observed in the southern
hemisphere. This suggests a global north-south symmetry of the overall
cloud structure at Venus.
Notes for editors:
The VMC consortium includes the Max Planck Institute for Solar System
Research (MPS), the Institute of Planetary Research (IPF, DLR, Berlin),
and the Institute of Computer and Communication Network Engineering (IDA,
TU Braunschweig), all located in Germany.
For more information:
Dmitri Titov, VMC co-investigator
Max Planck Institute for Solar System Research, Germany
Email: Titov @ mps.mpg.de
Richard Moissl, VMC co-investigator
Max Planck Institute for Solar System Research, Germany
Email: Moissl @ mps.mpg.de
Wojciech Markiewicz, VMC Principal Investigator
Max Planck Institute for Solar System Research, Germany
Email: Markiewicz @ mps.mpg.de
Håkan Svedhem, ESA Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaCP/SEM49DNKRGF_index_1.html ]
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