Andrew Yee[_1_]
February 7th 08, 04:29 AM
ESA News
http://www.esa.int
4 February 2008
Venus Express seeks out gases below the clouds
ESA's Venus Express has recently 'peeled back' the thick clouds around Venus
to provide the most accurate and wide-ranging map of water vapour and other
gases in the lower atmosphere to date.
As a planet, Venus does not radiate a significant amount of visible light.
But because of the searing temperatures below its thick cloud layer,
reaching 200 C at an altitude of 35 km and more than 450 C at the surface,
there is great deal of infrared radiation coming from beneath.
At certain wavelengths, or infrared 'windows', this radiation can pass
through the thick clouds, carrying information on what lies below. For
example, its intensity, and how it peaks or dips at certain wavelengths, can
tell us a lot about the composition of the atmosphere.
Thanks to the unique ability of its VIRTIS spectrometer to use these
spectral windows, Venus Express has mapped the atmosphere over many orbits
and has covered the lower atmosphere for the first time.
The atmosphere of Venus is dominated by carbon dioxide but as VIRTIS looked
on, it detected the signature of carbon monoxide, an unusual find in the
planet's deep atmosphere. Looking further, in higher resolution, scientists
also found carbonyl sulphide and water vapour. Since the early 1980s these
molecules were known to exist on Venus, but before Venus Express they had
never been measured and mapped so extensively and accurately.
Carbon monoxide is such a rarity on Venus that it can be used as a tracer to
monitor circulation patterns in the atmosphere. It is like studying the flow
of fluorescent ink dropped into a liquid to reveal the circulation pattern
in the liquid itself.
The presence of carbonyl sulphide is usually linked to carbon monoxide:
wherever there is abundant carbonyl sulphide, there will be little carbon
monoxide and vice versa. Past observations have already suggested that this
is the case, and VIRTIS has mapped the distribution with greater accuracy.
The results confirm what meteorological models have shown: that such an
inverse relationship between the abundances of molecules is due to the
large-scale circulation of the atmosphere. The air rises at the equator to
higher altitudes and moves towards higher latitudes, both north and south,
where it descends, transporting the gases as it goes along.
The existence and abundance of water vapour in Venus's atmosphere has been a
subject of debate for many years because the molecule is very difficult to
monitor in the lower atmosphere from space. Venus Express has now detected
and measured and mapped the amount of water vapour in the lower atmosphere,
with unprecedented spatial resolution.
Notes for editors:
The findings have been reported in 'Variability of CO, OCS And H2O Below The
Clouds of Venus From VIRTIS-H Night-side Spectra,' by E. Marcq, B. Bezard,
P. Drossart, G. Piccioni and the VIRTIS Team, presented at the American
Astronomical Society's Division of Planetary Sciences meeting in October
2007.
For more information:
Pierre Drossart, Observatoire de Paris, France
Email : Pierre.Drossart @ obspm.fr
Giuseppe Piccioni, IASF-INAF, Italy
Email : Giuseppe.Piccioni @ iasf-roma.inaf.it
Hakan Svedhem, ESA Venus Express Project Scientist
Email : Hakan.Svedhem @ esa.int
[NOTE: Images supporting this release are available at
http://www.esa.int/esaSC/SEMMJ432VBF_index_1.html ]
http://www.esa.int
4 February 2008
Venus Express seeks out gases below the clouds
ESA's Venus Express has recently 'peeled back' the thick clouds around Venus
to provide the most accurate and wide-ranging map of water vapour and other
gases in the lower atmosphere to date.
As a planet, Venus does not radiate a significant amount of visible light.
But because of the searing temperatures below its thick cloud layer,
reaching 200 C at an altitude of 35 km and more than 450 C at the surface,
there is great deal of infrared radiation coming from beneath.
At certain wavelengths, or infrared 'windows', this radiation can pass
through the thick clouds, carrying information on what lies below. For
example, its intensity, and how it peaks or dips at certain wavelengths, can
tell us a lot about the composition of the atmosphere.
Thanks to the unique ability of its VIRTIS spectrometer to use these
spectral windows, Venus Express has mapped the atmosphere over many orbits
and has covered the lower atmosphere for the first time.
The atmosphere of Venus is dominated by carbon dioxide but as VIRTIS looked
on, it detected the signature of carbon monoxide, an unusual find in the
planet's deep atmosphere. Looking further, in higher resolution, scientists
also found carbonyl sulphide and water vapour. Since the early 1980s these
molecules were known to exist on Venus, but before Venus Express they had
never been measured and mapped so extensively and accurately.
Carbon monoxide is such a rarity on Venus that it can be used as a tracer to
monitor circulation patterns in the atmosphere. It is like studying the flow
of fluorescent ink dropped into a liquid to reveal the circulation pattern
in the liquid itself.
The presence of carbonyl sulphide is usually linked to carbon monoxide:
wherever there is abundant carbonyl sulphide, there will be little carbon
monoxide and vice versa. Past observations have already suggested that this
is the case, and VIRTIS has mapped the distribution with greater accuracy.
The results confirm what meteorological models have shown: that such an
inverse relationship between the abundances of molecules is due to the
large-scale circulation of the atmosphere. The air rises at the equator to
higher altitudes and moves towards higher latitudes, both north and south,
where it descends, transporting the gases as it goes along.
The existence and abundance of water vapour in Venus's atmosphere has been a
subject of debate for many years because the molecule is very difficult to
monitor in the lower atmosphere from space. Venus Express has now detected
and measured and mapped the amount of water vapour in the lower atmosphere,
with unprecedented spatial resolution.
Notes for editors:
The findings have been reported in 'Variability of CO, OCS And H2O Below The
Clouds of Venus From VIRTIS-H Night-side Spectra,' by E. Marcq, B. Bezard,
P. Drossart, G. Piccioni and the VIRTIS Team, presented at the American
Astronomical Society's Division of Planetary Sciences meeting in October
2007.
For more information:
Pierre Drossart, Observatoire de Paris, France
Email : Pierre.Drossart @ obspm.fr
Giuseppe Piccioni, IASF-INAF, Italy
Email : Giuseppe.Piccioni @ iasf-roma.inaf.it
Hakan Svedhem, ESA Venus Express Project Scientist
Email : Hakan.Svedhem @ esa.int
[NOTE: Images supporting this release are available at
http://www.esa.int/esaSC/SEMMJ432VBF_index_1.html ]