Archive for the ‘Venus’ Category

Venus Vortices Go For Chaotic Multi-Storey Strolls Around The Poles

Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Universidad del País Vasco (I. Garate-Lopez)

Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Universidad del País Vasco (I. Garate-Lopez)

A detailed study of Venus’ South Polar Vortex shows a much more chaotic and unpredictable cyclone than previously thought. The analysis reveals that the center of rotation of the vortex wanders around the pole differently at different altitude levels in the clouds of Venus. In its stroll around the Pole, in layers separated by 20 km, the vortex experiences unpredictable changes in its morphology.

The results of this study are published online in Nature Geoscience today.

The study, entitled ‘A chaotic long-lived vortex at the southern pole of Venus’, used infrared images from VIRTIS instrument onboard the European Space Agency’s Venus Express spacecraft. VIRTIS provides spectral images at different levels of the atmosphere and allows the observation of the lower and upper clouds of Venus.

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When A Planet Behaves Like A Comet

February 6, 2013 Leave a comment

A comparison of the ionosphere of Venus under different solar wind conditions. Credit: ESA/Wei et al. (2012)

A comparison of the ionosphere of Venus under different solar wind conditions. Credit: ESA/Wei et al. (2012)

ESA’s Venus Express has made unique observations of Venus during a period of reduced solar wind pressure, discovering that the planet’s ionosphere balloons out like a comet’s tail on its nightside. The ionosphere is a region of weakly electrically charged gas high above the main body of a planet’s atmosphere. Its shape and density are partly controlled by the internal magnetic field of the planet.

For Earth, which has a strong magnetic field, the ionosphere is relatively stable under a range of solar wind conditions. By comparison, Venus does not have its own internal magnetic field and relies instead on interactions with the solar wind to shape its ionosphere. The extent to which this shaping depends on the strength of the solar wind has been controversial, but new results from Venus Express reveal for the first time the effect of a very low solar wind pressure on the ionosphere of an unmagnetised planet.

As this significantly reduced solar wind hit Venus, Venus Express saw the planet’s ionosphere balloon outwards on the planet’s ‘downwind’ nightside, much like the shape of the ion tail seen streaming from a comet under similar conditions.

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Venus Transit And Lunar Mirror Could Help Astronomers Find Worlds Around Other Stars

December 19, 2012 Leave a comment

When Venus passes in front of the Sun it hides a part of our star’s rotating surface. Because of rotation, the spectrum of the Sun (created splitting the different colours of light using a spectrograph) is slightly different on each side. On one side, the solar surface is rotating towards the observer and so its light will be ‘blueshifted’, meaning the lines seen in a spectrum move towards shorter wavelengths. On the other, the surface is rotating away from the observer, so its light is ‘redshifted’, meaning that the lines move towards longer wavelengths.

By looking at the reflected light from the lunar surface, this is averaged out as a broadening of the various lines. When Venus moves in front of the Sun from east to west, it first blocks out the surface moving towards us and then the surface moving away from us. This causes a distortion in the spectral lines known as the “Rossiter-McLaughlin effect”.

The astronomers realised that the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph installed on a 3.6m telescope at La Silla in Chile, part of the European Southern Observatory (ESO), would be sensitive enough to detect the effect and that the Moon would be in the right place too. The Moon was slightly ahead of the Earth in its orbit, so ‘saw’ the transit a couple of hours later than terrestrial observers. This also meant that the Moon was in the night time sky in Chile, making it possible for the La Silla telescope to operate safely and observe the change in the solar spectrum.

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Have Venusian Volcanoes Been Caught In The Act?

December 3, 2012 Leave a comment

Rise and fall of sulphur dioxide. Credits: Data: E. Marcq et al. (Venus Express); L. Esposito et al. (earlier data); background image: ESA/AOES Medialab

Rise and fall of sulphur dioxide. Credits: Data: E. Marcq et al. (Venus Express); L. Esposito et al. (earlier data); background image: ESA/AOES Medialab

Six years of observations by ESA’s Venus Express have shown large changes in the sulphur dioxide content of the planet’s atmosphere, and one intriguing possible explanation is volcanic eruptions. The thick atmosphere of Venus contains over a million times as much sulphur dioxide as Earth’s, where almost all of the pungent, toxic gas is generated by volcanic activity.

Most of the sulphur dioxide on Venus is hidden below the planet’s dense upper cloud deck, because the gas is readily destroyed by sunlight. That means any sulphur dioxide detected in Venus’ upper atmosphere above the cloud deck must have been recently supplied from below.

A previous analysis of infrared radiation from the surface pointed to lava flows atop a volcano with a composition distinct from those of their surroundings, suggesting that the volcano had erupted in the planet’s recent past. Now, an analysis of sulphur dioxide concentration in the upper atmosphere over six years provides another clue.

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A Curious Cold Layer In The Atmosphere Of Venus

October 1, 2012 Leave a comment

Credits: ESA/MPS, Katlenburg-Lindau, Germany

Venus Express has spied a surprisingly cold region high in the planet’s atmosphere that may be frigid enough for carbon dioxide to freeze out as ice or snow.

The planet Venus is well known for its thick, carbon dioxide atmosphere and oven-hot surface, and as a result is often portrayed as Earth’s inhospitable evil twin.

But in a new analysis based on five years of observations using ESA’s Venus Express, scientists have uncovered a very chilly layer at temperatures of around –175ºC in the atmosphere 125 km above the planet’s surface.

The curious cold layer is far frostier than any part of Earth’s atmosphere, for example, despite Venus being much closer to the Sun.

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Transit of Venus Causes Mass Transit to NASA Ames

June 18, 2012 Leave a comment

Approximately 6,000 astronomy enthusiasts of all ages gathered at NASA’s Ames Research Center, Moffett Field, Calif. to view Venus cross in front of, or transit, the sun. People from all around the Bay Area — as well as one dedicated enthusiast who came from Seattle specifically for the transit — were drawn to Ames for its unique educational and viewing opportunities pertaining to the rare celestial event that took place on June 5, 2012, and will not occur again until December 2117.
At the beginning of the program, attendees perused exhibits set up within the visitor center, gleaning information about astronauts and life in space. The vast amount of people interested in learning about the solar event crowded the room to the extent that additional chairs were brought up from storage to accommodate them, and people needed to be counted at the door to prevent the center from exceeding maximum capacity. Once inside, children eagerly poked their heads through astronaut cutouts and walked through a model of the International Space Station interior as their parents snapped photos. Natalie Batalha, Kepler mission scientist at Ames, gave a talk about how astronomers are using transit events today to search for other worlds beyond our galaxy. After the talk, attention turned to the live NASA TV feed of the event from atop Mauna Kea in Hawaii. Videos on the history of Venus and its major contributors, including 17th century German astronomer and mathematician Johannes Kepler, were featured in the programming.

Cook’s View Of The Transit Of Venus

Exactly 243 years ago, Captain James Cook made the sketch you see above. On June 5–6, 2012, you could make your own drawing of such a rare celestial event (provided you have the right eye-protecting equipment). But don’t miss the chance, as you won’t get another one for 115 years.

Cook’s drawing shows the Transit of Venus as it appeared on June 3, 1769, from Tahiti. During first voyage around the world, Cook, astronomer Charles Green, and the crew of the HMS Endeavour set up observing equipment on what is now known as Point Venus. In fact, the Transit was one of the motivations for the expedition, as it would provide valuable information for determining the size of our solar system. The explorers made many measurements of the event, and Green added his own sketch (see the downloadable large image).

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