Andrew Yee[_1_]
March 12th 08, 06:04 AM
ESA News
http://www.esa.int
21 February 2008
The light and dark of Venus
Venus Express has revealed a planet of extraordinarily changeable and
extremely large-scale weather. Bright hazes appear in a matter of days,
reaching from the south pole to the low southern latitudes and disappearing
just as quickly. Such 'global weather', unlike anything on Earth, has given
scientists a new mystery to solve.
The cloud-covered world of Venus is all but a featureless, unchangeable
globe at visible wavelengths of light. Switch to the ultraviolet and it
reveals a truly dynamic nature. Transient dark and bright markings stripe
the planet, indicating regions where solar ultraviolet radiation is absorbed
or reflected, respectively.
Venus Express watches the behaviour of the planet's atmosphere with its
Venus Monitoring Camera (VMC). It has seen some amazing things. In July
2007, VMC captured a series of images showing the development of the bright
southern haze. Within days, the high-altitude veil continually brightened
and dimmed, moving towards equatorial latitudes and back towards the pole
again.
Such global weather suggests that fast dynamical, chemical and microphysical
processes are at work on the planet. During these episodes, the brightness
of the southern polar latitudes increased by about a third and faded just as
quickly, as sulphuric acid particles coagulate.
"This bright haze layer is made of sulphuric acid," says Dmitri Titov, VMC
Co-Investigator and Venus Express Science Coordinator, Max Planck Institute
for Solar System Research, Germany. That composition suggests the existence
of a formation process to the VMC team.
At an altitude of about 70 km and below, Venus' carbon dioxide-rich
atmosphere contains small amounts of water vapour and gaseous sulphur
dioxide. These are usually buried in the cloud layer that blocks our view of
the surface at visible wavelengths.
However, if some atmospheric process lifts these molecules high up above the
cloud tops, they are exposed to solar ultraviolet radiation. This breaks the
molecules, making them highly reactive. The fragments find each other and
combine quickly to form sulphuric acid particles, creating the haze.
"The process is a bit similar to what happens with urban smog over cities,"
says Titov. With over 600 orbits completed, the VMC team now plan to look
for repeating patterns of behaviour in the build-up and decrease of the haze
layer.
What causes the water vapour and sulphur dioxide to well up in the first
place? The team does not know yet. Titov says that it is probably an
internal dynamical process in the planet's atmosphere. Also, the influence
of solar activity on haze formation has not been completely ruled out.
When the team have worked out what causes the hazes and their vigorous
dynamics, there is still another problem waiting to be solved. The dark
markings on these images are one of the biggest remaining mysteries of
Venus' atmosphere. They are caused by some chemical species, absorbing solar
ultraviolet radiation. However, as yet, planetary scientists do not know the
identity of the chemical. Now that they can spot these dark patches quickly
with VMC, the team hopes to use another Venus Express instrument, VIRTIS, to
pinpoint the exact chemical composition of these regions.
Notes for editors:
The VMC consortium includes:
The Max Planck Institute for Solar System Research (MPS), Germany The
Institute of Planetary Research (IPF, DLR, Berlin) Institute of Computer and
Communication Network Engineering (IDA, TU Braunschweig, Germany)
For more information:
Dmitri Titov, Max Planck Institute for Solar System Research, Germany
Email: Titov @ mps.mpg.de
Wojtek Markiewicz, Max Planck Institute for Solar System Research, Germany
Email: Markiewicz @ mps.mpg.de
Hakan 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/esaSC/SEMIVTVHJCF_index_1.html ]
http://www.esa.int
21 February 2008
The light and dark of Venus
Venus Express has revealed a planet of extraordinarily changeable and
extremely large-scale weather. Bright hazes appear in a matter of days,
reaching from the south pole to the low southern latitudes and disappearing
just as quickly. Such 'global weather', unlike anything on Earth, has given
scientists a new mystery to solve.
The cloud-covered world of Venus is all but a featureless, unchangeable
globe at visible wavelengths of light. Switch to the ultraviolet and it
reveals a truly dynamic nature. Transient dark and bright markings stripe
the planet, indicating regions where solar ultraviolet radiation is absorbed
or reflected, respectively.
Venus Express watches the behaviour of the planet's atmosphere with its
Venus Monitoring Camera (VMC). It has seen some amazing things. In July
2007, VMC captured a series of images showing the development of the bright
southern haze. Within days, the high-altitude veil continually brightened
and dimmed, moving towards equatorial latitudes and back towards the pole
again.
Such global weather suggests that fast dynamical, chemical and microphysical
processes are at work on the planet. During these episodes, the brightness
of the southern polar latitudes increased by about a third and faded just as
quickly, as sulphuric acid particles coagulate.
"This bright haze layer is made of sulphuric acid," says Dmitri Titov, VMC
Co-Investigator and Venus Express Science Coordinator, Max Planck Institute
for Solar System Research, Germany. That composition suggests the existence
of a formation process to the VMC team.
At an altitude of about 70 km and below, Venus' carbon dioxide-rich
atmosphere contains small amounts of water vapour and gaseous sulphur
dioxide. These are usually buried in the cloud layer that blocks our view of
the surface at visible wavelengths.
However, if some atmospheric process lifts these molecules high up above the
cloud tops, they are exposed to solar ultraviolet radiation. This breaks the
molecules, making them highly reactive. The fragments find each other and
combine quickly to form sulphuric acid particles, creating the haze.
"The process is a bit similar to what happens with urban smog over cities,"
says Titov. With over 600 orbits completed, the VMC team now plan to look
for repeating patterns of behaviour in the build-up and decrease of the haze
layer.
What causes the water vapour and sulphur dioxide to well up in the first
place? The team does not know yet. Titov says that it is probably an
internal dynamical process in the planet's atmosphere. Also, the influence
of solar activity on haze formation has not been completely ruled out.
When the team have worked out what causes the hazes and their vigorous
dynamics, there is still another problem waiting to be solved. The dark
markings on these images are one of the biggest remaining mysteries of
Venus' atmosphere. They are caused by some chemical species, absorbing solar
ultraviolet radiation. However, as yet, planetary scientists do not know the
identity of the chemical. Now that they can spot these dark patches quickly
with VMC, the team hopes to use another Venus Express instrument, VIRTIS, to
pinpoint the exact chemical composition of these regions.
Notes for editors:
The VMC consortium includes:
The Max Planck Institute for Solar System Research (MPS), Germany The
Institute of Planetary Research (IPF, DLR, Berlin) Institute of Computer and
Communication Network Engineering (IDA, TU Braunschweig, Germany)
For more information:
Dmitri Titov, Max Planck Institute for Solar System Research, Germany
Email: Titov @ mps.mpg.de
Wojtek Markiewicz, Max Planck Institute for Solar System Research, Germany
Email: Markiewicz @ mps.mpg.de
Hakan 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/esaSC/SEMIVTVHJCF_index_1.html ]