The transit of Venus in front of the sun is similar to a solar eclipse by the moon. It occurs when the planet passes directly between the sun and Earth, obscuring a small portion of the sun.

During the transit, people will see a small black dot moving across the sun, Wang Sichao of the Purple Mountain Observatory in Nanjing said.

However, observers should not watch the transit with the naked eye, he said, and eye protection measures are strongly recommended, China's state-run news agency Xinhua reported Wednesday.

In Beijing, the transit will start at 6:10 a.m. local time and last for over 6 hours before ending at 12:50 p.m., Wang said.

]]> Thu, 09 FEB 2012 08:59:28 AEST Paris (ESA) Oct 10, 2011 - ESA's Venus Express spacecraft has discovered an ozone layer high in the atmosphere of Venus. Comparing its properties with those of the equivalent layers on Earth and Mars will help astronomers refine their searches for life on other planets.

Venus Express made the discovery while watching stars seen right at the edge of the planet set through its atmosphere. Its SPICAV instrument analysed the starlight, looking for the characteristic fingerprints of gases in the atmosphere as they absorbed light at specific wavelengths.

The ozone was detectable because it absorbed some of the ultraviolet from the starlight.

Ozone is a molecule containing three oxygen atoms. According to computer models, the ozone on Venus is formed when sunlight breaks up carbon dioxide molecules, releasing oxygen atoms.

These atoms are then swept around to the nightside of the planet by winds in the atmosphere: they can then combine to form two-atom oxygen molecules, but also sometimes three-atom ozone molecules. "This detection gives us an important constraint on understanding the chemistry of Venus' atmosphere," says Franck Montmessin, who led the research.

It may also offer a useful comparison for searching for life on other worlds.

Ozone has only previously been detected in the atmospheres of Earth and Mars. On Earth, it is of fundamental importance to life because it absorbs much of the Sun's harmful ultraviolet rays. Not only that, it is thought to have been generated by life itself in the first place.

The build-up of oxygen, and consequently ozone, in Earth's atmosphere began 2.4 billion years ago. Although the exact reasons for it are not entirely understood, microbes excreting oxygen as a waste gas must have played an important role.

Along with plant life, they continue to do so, constantly replenishing Earth's oxygen and ozone.

As a result, some astrobiologists have suggested that the simultaneous presence of carbon dioxide, oxygen and ozone in an atmosphere could be used to tell whether there could be life on the planet.

This would allow future telescopes to target planets around other stars and assess their habitability. However, as these new results highlight, the amount of ozone is crucial.

The small amount of ozone in Mars' atmosphere has not been generated by life. There, it is the result of sunlight breaking up carbon dioxide molecules.

Venus too, now supports this view of a modest ozone build-up by non-biological means. Its ozone layer sits at an altitude of 100 km, about four times higher in the atmosphere than Earth's and is a hundred to a thousand times less dense.

Theoretical work by astrobiologists suggests that a planet's ozone concentration must be 20% of Earth's value before life should be considered as a cause.

These new results support that conclusion because Venus clearly remains below this threshold.

"We can use these new observations to test and refine the scenarios for the detection of life on other worlds," says Dr Montmessin.

Yet, even if there is no life on Venus, the detection of ozone there brings Venus a step closer to Earth and Mars. All three planets have an ozone layer.

"This ozone detection tells us a lot about the circulation and the chemistry of Venus' atmosphere," says Hakan Svedhem, ESA Project Scientist for the Venus Express mission.

"Beyond that, it is yet more evidence of the fundamental similarity between the rocky planets, and shows the importance of studying Venus to understand them all."

]]> Thu, 09 FEB 2012 08:59:28 AEST Paris (ESA) Oct 07, 2011 - Using observations of Venus performed with an instrument on ESA's Venus Express scientists have detected, for the first time, a tenuous layer of ozone in this planet's atmosphere. Located at an altitude of about 100 km, the layer is up to a thousand times less dense than the one found, at a lower altitude, in the Earth's stratosphere, but both are dominated by very similar chemical reactions.

The discovery poses new challenges to the characterisation of planetary atmospheres, especially in the quest for biomarkers on extrasolar planets.

Ozone (O3) is one of the most notable molecules populating the atmosphere of the Earth. Present there only in moderate quantities with respect to other, more abundant molecules-nitrogen, oxygen and carbon dioxide, among others-ozone plays an essential role in preserving life on Earth.

Mostly concentrated in a dense layer in the stratosphere, at altitudes between 15 and 50 km, atmospheric ozone absorbs the most energetic ultraviolet photons from the Sun, those which are harmful to living organisms. By absorbing this radiation, ozone is also responsible for the temperature inversion in the stratosphere.

The Earth's layer of ozone is a result of the large abundance of molecular oxygen (O2) in our planet's atmosphere. When irradiated by solar ultraviolet rays, oxygen molecules are broken into atoms, which may, in turn, react with other oxygen molecules and create ozone.

These reactions also take place in the atmosphere of other planets, as long as they harbour sufficient amounts of molecular oxygen. In fact, traces of ozone were first detected forty years ago in the tenuous atmosphere of Mars. Until now no evidence of this molecule had been found in the atmosphere of Venus, in spite of theoretical predictions.

At last, observations performed with one of the instruments on ESA's Venus Express spacecraft have now clearly identified a thin layer of ozone in the upper atmosphere of Venus. The results are reported in a paper published in the journal Icarus and are being presented at the European Planetology Network and Division for Planetary Sciences of the American Astronomical Society (EPSC-DPS) joint meeting, held this week in Nantes, France.

"We were surveying the atmosphere of Venus and focussing on other molecules when we stumbled on a very interesting feature in one of the spectra," comments Franck Montmessin from the Laboratoire Atmospheres, Milieux, Observations Spatiales (LATMOS) in Guyancourt, France. Montmessin led the team who carried out this study. "The spectral signature of ozone, a distinctive absorption band at UV wavelengths, was rather pronounced and we could clearly discern it in our plots with the naked eye," he adds.

The data have been gathered with the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument on board Venus Express using the stellar occultation method. This technique allows astronomers to indirectly probe a planet's atmosphere by studying its influence on the light from distant stars.

"As it orbits Venus, the spacecraft's line of sight to a given star crosses the planet's atmosphere, meaning that starlight is prone to being absorbed by the atmosphere," explains co-author Jean-Loup Bertaux from LATMOS and Universite de Versailles-Saint-Quentin, France. Bertaux is also the Principal investigator of SPICAV. "In the process, chemical species present in the atmosphere leave their characteristic signatures in the star's spectrum, enabling us to pinpoint them," he adds.

After they identified this first ozone feature in the spectrum from an orbit of Venus Express, the team of astronomers ran a dedicated search over data from nearly 300 orbits. The analysis revealed robust evidence for this molecule in about ten per cent of the orbits.

According to the new data, ozone is located at varying altitudes in the Venusian atmosphere, between 90 and 120 km, and is always confined to a rather thin layer, measuring 5 to 10 km across. "The varying altitude and narrow radial extent of the detected patches are particularly striking, hinting that an as-yet-undetermined mechanism must be keeping the ozone right there," notes Hakan Svedhem, ESA Venus Express Project Scientist.

The ozone layer on Venus is very tenuous-up to a thousand times less dense than that on Earth. Nonetheless, it could be readily detected using SPICAV because the stellar occultation method, by peering tangentially through the layers of the atmosphere, probes a large path of the atmosphere and is thus sensitive to chemical species even in low concentrations.

A drawback of the method, however, is that it relies on the availability of stars in the line of sight, meaning that it yields an uneven coverage of the planet and is limited to the night side. This means that investigations of the spatial or temporal distribution of ozone across the planet are not straightforward.

"Interestingly, we expected to detect ozone at the anti-solar point, where molecular oxygen is highly concentrated, but instead we found none there," comments Montmessin. As highlighted by previous studies based on Venus Express observations, sunlight illuminating the day side of the planet breaks apart the carbon dioxide molecules, liberating oxygen atoms.

These are then carried to the anti-solar point, on the night side, by the sub-solar-to-anti-solar circulation, a strong wind caused by the high temperature gradient between the two sides of Venus. Oxygen atoms transported to the anti-solar point give rise to molecular oxygen, and some production of ozone is also expected.

"The lack of ozone detected there is explained if the molecules are destroyed by chlorine-based compounds, which are funnelled to the anti-solar point by the same mechanism that draws the oxygen there," adds Montmessin. The chlorine-catalysed destruction of ozone at Venus' anti-solar point may be caused by reactions very similar to those responsible for the Antarctic 'ozone hole' on Earth, highlighting once again the similarity of atmospheric processes on these two planets.

Besides enabling comparative studies among the atmospheres of terrestrial planets, this discovery has intriguing implications for astrobiology and the quest for extrasolar planets. Future hunts for planetary systems beyond our own will characterise the atmosphere of these planets in search of biomarkers-chemical compounds, such as water, carbon dioxide and molecular oxygen, that are associated, on Earth, with living organisms.

Thus far, ozone has also been regarded as a potential biomarker, since it traces the distribution of molecular oxygen.

However, the detection of ozone in the atmosphere of Venus, a planet that clearly does not host life, raises questions about the unambiguity of biomarkers and will help assessing the role of chemical indicators of biological activity in future extrasolar planet searches.

The study presented here is based on data collected with the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument on board ESA's Venus Express spacecraft.

SPICAV is a remote-sensing spectrometer covering three distinct spectral regions (ultraviolet, near- and mid-infrared). It is used to probe the atmosphere of Venus above the clouds, which are located at an altitude of about 50-60 km.

Venus Express, Europe's first mission to Earth's twin world, is investigating the nature of our closest planetary neighbour. Launched from the Baikonur Cosmodrome in Kazakhstan on 9 November 2005 upon a Soyuz-Fregat launcher, it was inserted into Venus orbit on 11 April 2006, and is currently the only spacecraft in orbit around the planet.

F. Montmessin, et al., "A layer of ozone detected in the nightside upper atmosphere of Venus", 2011, Icarus, Volume 216, Issue 1, November 2011, Pages 82-85. DOI:10.1016/j.icarus.2011.08.010.

]]> Thu, 09 FEB 2012 08:59:28 AEST Greenbelt MD (SPX) Sep 28, 2011 - At first glance, a weather forecaster for Venus would have either a really easy or a really boring job, depending on your point of view. The climate on Venus is widely known to be unpleasant - at the surface, the planet roasts at more than 800 degrees Fahrenheit under a suffocating blanket of sulfuric acid clouds and a crushing atmosphere more than 90 times the pressure of Earth's. Intrepid future explorers should abandon any hope for better days, however, because it won't change much.

"Any variability in the weather on Venus is noteworthy, because the planet has so many features to keep atmospheric conditions the same," says Dr. Tim Livengood, a researcher with the National Center for Earth and Space Science Education, Capitol Heights, Md., and now with the University of Maryland, College Park, Md.

"Earth has seasons because its rotation axis is tilted by about 23 degrees, which changes the intensity of sunlight and the length of the day in each hemisphere throughout the year. However, Venus has been tilted so much, it's almost completely upside down, leaving it with a net tilt of less than three degrees from the sun, so the seasonal effect is negligible," explains Livengood, who is stationed at NASA's Goddard Space Flight Center in Greenbelt, Md.

"Also, its orbit is even more circular than Earth's, which prevents it from getting significantly hotter or cooler by moving closer to or further away from the sun. And while you might expect things to cool down at night - especially since Venus rotates so slowly that its night lasts almost two Earth months - the thick atmosphere and sulfuric acid clouds act like a blanket while winds move heat around, keeping temperatures pretty even. Finally, almost all the planet's water has escaped to space, so you don't get any storms or precipitation like on Earth where water evaporates and condenses as clouds."

However, higher up, the weather gets more interesting, according to a new study of old data by NASA and international scientists. The team detected strange things going on in data from telescopic observations of Venus in infrared light at about 68 miles (110 kilometers) above the planet's surface, in cold, clear air above the acid clouds, in two layers called the mesosphere and the thermosphere.

"Although the air over the polar regions in these upper atmospheric layers on Venus was colder than the air over the equator in most measurements, occasionally it appeared to be warmer," said Dr. Theodor Kostiuk of NASA Goddard.

"In Earth's atmosphere, a circulation pattern called a 'Hadley cell' occurs when warm air rises over the equator and flows toward the poles, where it cools and sinks. Since the atmosphere is denser closer to the surface, the descending air gets compressed and warms the upper atmosphere over Earth's poles. We saw the opposite on Venus.

In addition, although the surface temperature is fairly even, we've seen substantial changes - up to 54 degrees Fahrenheit (about 30 K change) - within a few Earth days in the mesosphere - thermosphere layers over low latitudes on Venus. The poles appeared to be more stable, but we still saw changes up to 27 degrees Fahrenheit (about 15 K change)."

Kostiuk and Livengood are co-authors of a paper about these observations that appeared July 23 in the online edition of the journal Icarus.

"The mesosphere and thermosphere of Venus are dynamically active," said lead author Dr. Guido Sonnabend of the University of Cologne, Germany. "Wind patterns resulting from solar heating and east to west zonal winds compete, possibly resulting in altered local temperatures and their variability over time."

This upper atmospheric variability could have many possible causes, according to the team. Turbulence from global air currents at different altitudes flowing at more than 200 miles per hour in opposite directions could exchange hot air from below with cold air from above to force changes in the upper atmosphere. Also, giant vortexes swirl around each pole. They, too, could generate turbulence and change the pressure, causing the temperature to vary.

Since the atmospheric layers the team observed are above the cloud blanket, they may be affected by changes in sunlight intensity as day transitions to night, or as latitude increases toward the poles. These layers are high enough that they could even be affected by solar activity (the solar cycle), such as solar explosions called flares and eruptions of solar material called coronal mass ejections.

Changes were seen over periods spanning days, to weeks, to a decade. Temperatures measured in 1990-91 are warmer than in 2009. Measurements obtained in 2007 using Goddard's Heterodyne Instrument for Planetary Wind and Composition (HIPWAC) observed warmer temperature in the equatorial region than in 2009. Having seen that the atmosphere can change, a lot more observations are needed to determine how so many phenomena can affect Venus' upper atmosphere over different intervals, according to the team.

"In addition to all these changes, we saw warmer temperatures than those predicted for this altitude by the leading accepted model, the Venus International Reference Atmosphere model," said Kostiuk.

"This tells us that we have lots of work to do updating our upper atmospheric circulation model for Venus." Although Venus is often referred to as Earth's twin, since they are almost the same size, it ended up with a climate very different from Earth. A deeper understanding of Venus' atmosphere will let researchers compare it to the evolution of Earth's atmosphere, giving insight as to why Earth now teems with life while Venus suffered a hellish fate.

The team measured temperature and wind speeds in Venus' upper atmosphere by observing an infrared glow emitted by carbon dioxide (CO2) molecules when they were energized by light from the sun. Infrared light is invisible to the human eye and is perceived by us as heat, but it can be detected by special instruments.

In the research, it appeared as a line on a graph from a spectrometer, an instrument that separates light into its component colors, each of which corresponds to a specific frequency. The width of the line revealed the temperature, while shifts in its frequency gave the wind speed.

The researchers compared observations from 1990 and 1991 using Goddard's Infrared Heterodyne Spectrometer instrument at NASA's Infrared Telescope Facility on Mauna Kea, Hawaii, to observations from 2009 using the Cologne Tunable Heterodyne Infrared Spectrometer instrument at the National Optical Astronomy Observatory's McMath Telescope at Kitt Peak, Ariz.

]]> Thu, 09 FEB 2012 08:59:28 AEST Tokyo (AFP) Sept 8, 2011 - Japan on Thursday said it had successfully test-fired the engine of its "Akatsuki" space probe in preparation for a renewed attempt to get it into orbit around Venus in 2015.

Following December's failed attempt to send the probe to the second planet from the sun, a remote test ignition conducted Wednesday lasted for 2 seconds as planned, the Japan Aerospace Exploration Agency (JAXA) said.

"The failure in December was highly likely due to engine damage," said JAXA spokesman Eijiro Namura.

"We have made the first step forward by igniting the engine for the first time since then," to assess its condition, he said.

The "Akatsuki", meaning "Dawn" is fitted with two paddle-shaped solar panels and blasted off in May last year on a 25.2 billion yen ($300 million) mission to observe the toxic atmosphere and super-hot volcanic surface of Venus.

But in a setback for Japan's space programme, the box-shaped probe failed to enter the planet's gravitational pull and shot past it in December. It is still in space.

Another, longer engine test ignition of the probe -- officially known as the Planet-C Venus Climate Orbiter -- is planned for September 14.

Based on the test results, JAXA plans to fire up the engine in early November in order to adjust the craft's positioning ahead of the next available window for a Venus orbit attempt in 2015 or later, according to the agency.

Scientists believe that investigating the climate of Venus would deepen their understanding of the formation of the Earth's environment and its future.

]]> Thu, 09 FEB 2012 08:59:28 AEST Washington (UPI) Sep 2, 2011 - Scientists studying Venus say NASA has a bias against the planet when it come to scientific missions and infrequent visits are hindering their research.

Venus researchers voiced their frustrations at the annual meeting of NASA's Venus Exploration Analysis Group near Washington this week, the journal Nature reported.

There hasn't been a U.S. mission to Venus since the Magellan probe radar-mapped its surface in the early 1990s, they noted, and NASA recently rejected a number of Venus research proposals.

NASA has denied any bias.

"There were just better proposals" for other Solar System targets, Jim Green, director of planetary science at NASA, said.

Venus researchers were upset.

"A lot of us are dismayed," says David Grinspoon, astrobiology curator at the Denver Museum of Nature and Science, a co-investigator on several of the proposals.

Research grants allocated to Venus studies have made up just 2 percent of NASA's planetary-science funding since 2005.

Without new missions supplying data for research, funding for Venus studies has dwindled, leading to fewer students entering the field, Grinspoon said -- which mean a smaller group of researchers to lobby for missions.

"Because of this feedback loop, the community has shrunk," he said.

]]> Thu, 09 FEB 2012 08:59:28 AEST Paris, France (ESA) Apr 11, 2011 - New analysis of images taken by ESA's Venus Express orbiter has revealed surprising details about the remarkable, shape-shifting collar of clouds that swirls around the planet's South Pole. This fast-moving feature is all the more surprising since its centre of rotation is typically offset from the geographical pole. The results of this study are published online in Science Express.

Several planets in the Solar System, including Earth, have been found to possess hurricane-like polar vortices, where clouds and winds rotate rapidly around the poles. Some of these take on strange shapes, such as the hexagonal structure on Saturn, but none of them are as variable or unstable as the southern polar vortex on Venus.

Scientists have known about the presence of swirling clouds around the poles of Venus since they were first imaged by Mariner 10 in 1974. At the same time, it was discovered that Venus' upper winds sweep westwards around the planet in only four days, 60 times faster than the rotation of the solid surface of the planet - a phenomenon known as superrotation.

Thermal infrared imagery from the Pioneer Venus spacecraft subsequently revealed an enormous depression in the cloud blanket at the North Pole. This relatively warm polar 'hole' was thought to be caused by downward movement of gases, rather like water flowing down a drain. However, detailed examination of the thick clouds and dense atmosphere over the South Pole had to wait until the arrival of Venus Express in April 2006.

During its first orbit around the planet, multi-wavelength observations confirmed for the first time the presence of a huge 'double-eye' atmospheric vortex at the planet's South Pole. Some 2000 km across, it was comparable to the structure that had previously been detected at the North Pole.

Since then, high-resolution infrared measurements obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on Venus Express have revealed that the southern vortex is far more complex than previously believed. The VIRTIS images, taken at wavelengths of 3.8 and 5.0 microns, are ideal for tracking polar features on both the day and night sides of the planet, probing the polar cloud layer at an altitude of about 65 km.

The new observations, reported this week in the journal Science on the Science Express website, show that the vortex has a highly variable shape and internal structure. Images show that its morphology is constantly changing on timescales of less than 24 hours, as a result of differential rotation.

"The southern vortex is very dynamic compared with a hurricane on Earth, which remains stable for several days," said Hakan Svedhem, ESA's Venus Express Project Scientist. "It can take almost any shape, so although it often looks like an 'S' or figure 8, it may become completely irregular, even chaotic, in appearance."

The rapid shape changes indicate complex weather patterns, which are strongly influenced by the fact that the centre of the vortex does not coincide with the geographical pole.

The VIRTIS images show that the speeds of the zonal (east-west) winds change rapidly with latitude, revealing that the vortex is continually being pulled and stretched by wind shear. Although the mean zonal wind is retrograde (blowing from east to west) and approximately uniform equatorward of 84 degrees S, its speed decreases toward the pole and becomes prograde (blowing from west to east) close to 87 degrees S. A slightly slower wind is detected at 75 degrees S, coinciding with the poleward edge of the cloud collar which coincides with a region of colder air surrounding the centre of the vortex.

The apparent reversal of the zonal wind close to the pole is a consequence of the non-alignment of the centre of rotation of the vortex with the planet's rotational axis. This causes an apparent inversion of the wind direction between the pole and the centre of rotation.

The new analysis also reveals that the centre of rotation of the vortex drifts right around the pole over a period of 5-10 Earth days. Its average displacement from the geographical South Pole is about three degrees of latitude, or several hundred kilometres. The data show no evidence of any link between the positions of these 'centroids' and local solar times, as might result from a solar tide-related forcing of the superrotation.

"Our results highlight the importance of the polar region in the global dynamics of the Venus atmosphere," said David Luz of the Centre for Astronomy and Astrophysics at the University of Lisbon, Portugal, the lead author of the Science paper. "They provide new insights into the complex processes that shape the polar vortices and their role in the atmosphere's superrotation."

The Venus Express mission is currently funded until 2014, offering further opportunities for in-depth studies of the super-rotating atmosphere and the shape-shifting southern polar vortex. However, its highly elliptical orbit means that Venus Express flies too close to the planet's North Pole for detailed imaging studies of its other polar vortex.

"It seems likely that the northern polar vortex has a similar structure and behaves in a similar way," noted Svedhem. "However, the spacecraft flies very close to the North Pole, so it can only see a small region. Confirmation of the behaviour of the northern vortex will have to wait until future missions."

"Results such as these show how interesting Venus is to study and how important it is to study other worlds," Svedhem added. "They enable us to compare the processes that take place on Venus, a planet with a thick atmosphere, with those on our Earth."

The results of this study are published online in Science Express on 7 April 2011. Other authors of the paper were: by D.L. Berry of the University of Evora, Portugal; G. Piccioni and R. Politi of INAF-IASF Rome, Italy; P. Drossart and S. Erard from Observatoire de Paris, France; C.F. Wilson of Oxford University, United Kingdom; and F. Nuccilli from INAF-IFSI Rome, Italy. Reference publication Luz, D., et al., "Venus's Southern Polar Vortex Reveals Precessing Circulation", published online on Science Express, 7 April 2011. DOI:10.1126/science.1201629

]]> Thu, 09 FEB 2012 08:59:28 AEST Paris, France (ESA) Apr 08, 2011 - New analysis of images taken by ESA's Venus Express orbiter has revealed surprising details about the remarkable, shape-shifting collar of clouds that swirls around the planet's South Pole. This fast-moving feature is all the more surprising since its centre of rotation is typically offset from the geographical pole. The results of this study are published online in Science Express.

Several planets in the Solar System, including Earth, have been found to possess hurricane-like polar vortices, where clouds and winds rotate rapidly around the poles. Some of these take on strange shapes, such as the hexagonal structure on Saturn, but none of them are as variable or unstable as the southern polar vortex on Venus.

Scientists have known about the presence of swirling clouds around the poles of Venus since they were first imaged by Mariner 10 in 1974. At the same time, it was discovered that Venus' upper winds sweep westwards around the planet in only four days, 60 times faster than the rotation of the solid surface of the planet - a phenomenon known as superrotation.

Thermal infrared imagery from the Pioneer Venus spacecraft subsequently revealed an enormous depression in the cloud blanket at the North Pole. This relatively warm polar 'hole' was thought to be caused by downward movement of gases, rather like water flowing down a drain. However, detailed examination of the thick clouds and dense atmosphere over the South Pole had to wait until the arrival of Venus Express in April 2006.

During its first orbit around the planet, multi-wavelength observations confirmed for the first time the presence of a huge 'double-eye' atmospheric vortex at the planet's South Pole. Some 2000 km across, it was comparable to the structure that had previously been detected at the North Pole.

Since then, high-resolution infrared measurements obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on Venus Express have revealed that the southern vortex is far more complex than previously believed.

The VIRTIS images, taken at wavelengths of 3.8 and 5.0 microns, are ideal for tracking polar features on both the day and night sides of the planet, probing the polar cloud layer at an altitude of about 65 km.

The new observations, reported this week in the journal Science on the Science Express website, show that the vortex has a highly variable shape and internal structure. Images show that its morphology is constantly changing on timescales of less than 24 hours, as a result of differential rotation.

"The southern vortex is very dynamic compared with a hurricane on Earth, which remains stable for several days," said Hakan Svedhem, ESA's Venus Express Project Scientist. "It can take almost any shape, so although it often looks like an 'S' or figure 8, it may become completely irregular, even chaotic, in appearance."

The rapid shape changes indicate complex weather patterns, which are strongly influenced by the fact that the centre of the vortex does not coincide with the geographical pole.

The VIRTIS images show that the speeds of the zonal (east-west) winds change rapidly with latitude, revealing that the vortex is continually being pulled and stretched by wind shear.

Although the mean zonal wind is retrograde (blowing from east to west) and approximately uniform equatorward of 84 degrees S, its speed decreases toward the pole and becomes prograde (blowing from west to east) close to 87 degrees S. A slightly slower wind is detected at 75 degrees S, coinciding with the poleward edge of the cloud collar which coincides with a region of colder air surrounding the centre of the vortex.

The apparent reversal of the zonal wind close to the pole is a consequence of the non-alignment of the centre of rotation of the vortex with the planet's rotational axis. This causes an apparent inversion of the wind direction between the pole and the centre of rotation.

The new analysis also reveals that the centre of rotation of the vortex drifts right around the pole over a period of 5-10 Earth days. Its average displacement from the geographical South Pole is about three degrees of latitude, or several hundred kilometres. The data show no evidence of any link between the positions of these 'centroids' and local solar times, as might result from a solar tide-related forcing of the superrotation.

"Our results highlight the importance of the polar region in the global dynamics of the Venus atmosphere," said David Luz of the Centre for Astronomy and Astrophysics at the University of Lisbon, Portugal, the lead author of the Science paper. "They provide new insights into the complex processes that shape the polar vortices and their role in the atmosphere's superrotation."

The Venus Express mission is currently funded until 2014, offering further opportunities for in-depth studies of the super-rotating atmosphere and the shape-shifting southern polar vortex. However, its highly elliptical orbit means that Venus Express flies too close to the planet's North Pole for detailed imaging studies of its other polar vortex.

"It seems likely that the northern polar vortex has a similar structure and behaves in a similar way," noted Svedhem. "However, the spacecraft flies very close to the North Pole, so it can only see a small region. Confirmation of the behaviour of the northern vortex will have to wait until future missions."

"Results such as these show how interesting Venus is to study and how important it is to study other worlds," Svedhem added. "They enable us to compare the processes that take place on Venus, a planet with a thick atmosphere, with those on our Earth."

]]> Thu, 09 FEB 2012 08:59:28 AEST Tokyo (UPI) Jan 6, 2011 - A Japanese space probe that failed to enter orbit around Venus may get a chance to redeem itself earlier than its controllers first thought, officials said.

The Japan Aerospace Exploration Agency says it may be possible to make another attempt to send the Akatsuki spacecraft into orbit around Venus five years from now instead of six as previously believed, SPACE.com reported Thursday.

The $300 million Akatsuki spacecraft overshot Venus when its thrusters, meant to fire for 12 minutes in an orbital-insertion burn, shut down after just 2-1/2 minutes.

An unexpected pressure drop in the spacecraft's fuel line, or possibly damage to the probe's engine nozzle, are the likely causes, JAXA scientists say.

JAXA had said it would try again in six years, when Akatsuki approaches Venus once again, but now say it may be possible to decelerate Akatsuki slowly to let Venus catch up and try for an orbit in five years.

Akatsuki was meant to spend at least two years orbiting Venus, studying its clouds, atmosphere and weather.

]]> Thu, 09 FEB 2012 08:59:28 AEST Tokyo (AFP) Dec 8, 2010 - A Japanese space probe has hurtled past Venus after failing to enter the planet's orbit as planned, the space agency said Wednesday, but it voiced hope for a successful rendezvous six years from now.

The "Akatsuki", or "Dawn", blasted off in May on a 300-million-dollar mission to observe the toxic atmosphere and super-hot volcanic surface of Venus, which is sometimes called the Earth's sister planet.

However, in a setback for Japan's space programme, the box-shaped golden probe failed to enter the planet's gravitational pull and shot past it, said the Japan Aerospace Exploration Agency (JAXA).

"It will come close to Venus again in roughly six years, giving us another opportunity," said JAXA spokesman Hitoshi Soeno, who stressed that ground control in Sagamihara near Tokyo was still in command of the probe.

Masato Nakamura, the chief developer of Akatsuki, said a second attempt was "highly doable", according to the Jiji Press news agency.

The Akatsuki, also called the Planet-C Venus Climate Orbiter, was sent on a mission to orbit and observe Venus for two years, working closely with the European Space Agency's Venus Express.

It is fitted with two paddle-shaped solar panels and five cameras to let it peer through the planet's thick layer of sulphuric acid clouds, and was also due to search for signs of lightning and for active volcanoes.

Venus is similar in size and age to Earth but has a far more hostile climate, scorching at around 460 degrees Celsius (860 degrees Fahrenheit) and with large amounts of carbon dioxide, the primary greenhouse gas on Earth.

Scientists believe that investigating the climate of Venus would deepen their understanding of the formation of the Earth's environment and its future.

The Japanese probe on Tuesday morning Japan time reversed its engine thrust to slow down and enter the gravitational field of Venus, said JAXA, which had Tuesday reported communication problems with the probe.

On Wednesday JAXA announced that its mission had failed.

"We started the manoeuvre to put the Venus probe Akatsuki into orbit around Venus at 8:49 am (Tokyo time) on December 7... but have confirmed that we could not put it into the orbit," it said in a statement.

The exact cause of the failure was not officially determined yet but one possible explanation was that the probe did not slow down enough near Venus to be pulled in by the planet's gravity, Soeno said.

Japan's top government spokesman Yoshito Sengoku said "it was very regrettable that the probe did not succeed in entering the orbit around Venus. We'd like to continue watching Akatsuki's situation."

The project has so far cost Japan about 24.4 billion yen (290 million dollars). Akatsuki cost 14.6 billion yen to develop and produce, while its rocket launch cost 9.8 billion yen.

Japan launched a Mars probe in 1998 but JAXA gave up on its attempt to put the probe, called "Nozomi" or "Hope", into the red planet's orbit in 2003 due to technical glitches.

The latest setback came after a landmark mission by "Hayabusa", which became the first-ever space probe to collect asteroid dust during a seven-year odyssey that ended with its return to Earth over the Australian desert in June.

The trip of Hayabusa, or Falcon, had been plagued with technical glitches but it managed to come home three years late.

earlier related report
Japan space probe failed to enter Venus orbit: JAXA
Tokyo (AFP) Dec 8, 2010 - An interplanetary probe intended to go into orbit around Venus has failed in its mission, Japan's space agency said Wednesday, 200 days after it left Earth.

"Akatsuki", or "Dawn", was intended to be the first Japanese satellite to orbit a planet other than Earth.

Officially called the Planet-C Venus Climate Orbiter, the box-shaped golden satellite fitted with two paddle-shaped solar panels had blasted off from a space centre in southern Japan in May.

It reversed its engine to slow down and enter the planet's gravitational field Tuesday, when it temporarily lost contact with ground control, the Japan Aerospace Exploration Agency (JAXA) said.

On Wednesday JAXA announced that its mission had failed -- although it immediately said it was considering another attempt in seven years' time.

"We started the manoeuvre to put the Venus probe Akatsuki into orbit around Venus at 8:49 am (Tokyo time) on December 7... but have confirmed that we could not put it into the orbit," JAXA said in a statement.

JAXA said it had set up a taskforce to investigate the cause of the failure.

Japan launched a Mars probe in 1998 but JAXA gave up on its attempt to put the probe, called "Nozomi" or "Hope", into orbit in 2003 after finding it impossible to overcome technical glitches.

Venus is similar in size and age to Earth but has a far more hostile climate, with temperatures around 460 degrees Celsius (860 degrees Fahrenheit) and large amounts of carbon dioxide, the primary greenhouse gas on Earth.

Scientists believe investigating the climate of Venus would help them deepen their understanding of the formation of the Earth's environment and its future.

The Akatsuki was fitted with five cameras to peer through the planet's thick layer of sulphuric acid clouds to monitor the meteorology of Venus, search for possible lightning, and scan its crust for active volcanoes.

Akatsuki was to work closely with the European Space Agency's Venus Express.

earlier related report
Japan's first Venus probe struggling to enter orbit
Tokyo (AFP) Dec 7, 2010 - Japan's first space probe bound for Venus was struggling on Tuesday to enter the planet's orbit, the space agency said.

The Planet-C Venus Climate Orbiter, a box-shaped golden satellite fitted with two paddle-shaped solar panels, blasted off from a space centre in southern Japan in May.

The probe, nicknamed "Akatsuki" or "Dawn", reversed its engine to slow down and enter the planet's gravitational field but lost contact with ground control longer than had been anticipated, the Japan Aerospace Exploration Agency (JAXA) said.

It was presumed to have shifted itself into a "safe hold mode", and was able to communicate only by via one of its three antennae after the blackout ended.

"It is not known which path the probe is following at the moment," JAXA official Munetaka Ueno told reporters at the ground control late Tuesday. "We are making maximum effort to readjust the probe."

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