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Post Info TOPIC: Venus Atmosphere
Blobrana


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RE: Venus Atmosphere
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Venus wave may be Solar System's biggest

A giant wave in the atmosphere of Venus may be the biggest of its kind in the Solar System.
The feature, observed by a Japanese spacecraft, is thought to be generated in a broadly similar way to the surface ripples that form as water flows over rocks on a stream bed. In this case, the wave is thought to form as the lower atmosphere flows over mountains on Venus' surface.
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Blobrana


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Title: Using the transit of Venus to probe the upper planetary atmosphere
Author: Fabio Reale, Angelo F. Gambino, Giuseppina Micela, Antonio Maggio, Thomas Widemann, Giuseppe Piccioni

The atmosphere of a transiting planet shields the stellar radiation providing us with a powerful method to estimate its size and density. In particular, because of their high ionization energy, atoms with high atomic number (Z) absorb short-wavelength radiation in the upper atmosphere, undetectable with observations in visible light. One implication is that the planet should appear larger during a primary transit observed in high energy bands than in the optical band. The last Venus transit in 2012 offered a unique opportunity to study this effect. The transit has been monitored by solar space observations from Hinode and Solar Dynamics Observatory (SDO). We measure the radius of Venus during the transit in three different bands with subpixel accuracy: optical (4500A), UV (1600A, 1700A), Extreme UltraViolet (EUV, 171-335A) and soft X-rays (about 10A). We find that, while the Venus optical radius is about 80 km larger than the solid body radius (the expected opacity mainly due to clouds and haze), the radius increases further by more than 70 km in the EUV and soft X-rays. These measurements mark the densest ion layers of Venus' ionosphere, providing information about the column density of CO2 and CO. They are useful for planning missions in situ to estimate the dynamical pressure from the environment, and can be employed as a benchmark case for observations with future missions, such as the ESA Athena, which will be sensitive enough to detect transits of exoplanets in high-energy bands.

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Blobrana


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Title: The Superrotation of Venus: Where's the Torque?
Author: Clifford Chafin

The superrotation of the atmosphere of Venus requires a large torque on the up- per atmosphere. Mechanisms for providing a net balancing of this through waves or ionospheric motions to other parts of the atmosphere have been proposed but all have difficulties. Here we demonstrate that the albedo gradient from the day to night side of the cloud layer allows a gradient of light pressure that is sufficient to provide an external torque to drive this flow.

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Blobrana


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The fast winds of Venus are getting faster

The most detailed record of cloud motion in the atmosphere of Venus chronicled by ESA's Venus Express has revealed that the planet's winds have steadily been getting faster over the last six years.
Venus is well known for its curious super-rotating atmosphere, which whips around the planet once every four Earth days.
By tracking the movements of distinct cloud features in the cloud tops some 70 km above the planet's surface over a period of 10 venusian years (6 Earth years), scientists have been able to monitor patterns in the long-term global wind speeds.
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Blobrana


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Southern pole of Venus
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Title: A chaotic long-lived vortex at the southern pole of Venus
Authors: I. Garate-Lopez, R. Hueso, A. Sánchez-Lavega, J. Peralta, G. Piccioni & P. Drossart

Polar vortices are common in the atmospheres of rapidly rotating planets. On Earth and Mars, vortices are generated by surface temperature gradients and their strength is modulated by the seasonal insolation cycle. Slowly rotating Venus lacks pronounced seasonal forcing, but vortices are known to occur at both poles, in an atmosphere that rotates faster than the planet itself. Here we report observations of cloud motions at altitudes of 42 and 63 km above Venus's south pole using infrared images from the VIRTIS instrument onboard the Venus Express spacecraft. We find that the south polar vortex is a long-lived but unpredictable feature. Within the two cloud layers sampled, the centres of rotation of the vortex are rarely aligned vertically and both wander erratically around the pole with velocities of up to 16 m s^-1. At the two horizontal levels, the observed cloud morphologies do not correlate with the vorticity of the wind field and change continuously, and vertical and meridional wind shears are also highly variable. We conclude that Venus's south polar vortex is a continuously evolving structure that is at least 20 km high, extending through a quasi-convective turbulent region.

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Blobrana


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Venus ionosphere
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When a planet behaves like a comet

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.
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Blobrana


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Venus troposphere
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Title: Ground-based near-infrared observations of water vapour in the Venus troposphere
Authors: S. Chamberlain, J. A. Bailey, D. Crisp, V. S. Meadows

We present a study of water vapour in the Venus troposphere obtained by modelling specific water vapour absorption bands within the 1.18 µm window. We compare the results with the normal technique of obtaining the abundance by matching the peak of the 1.18 µm window. Ground-based infrared imaging spectroscopy of the night side of Venus was obtained with the Anglo-Australian Telescope and IRIS2 instrument with a spectral resolving power of R ~ 2400. The spectra have been fitted with modelled spectra simulated using the radiative transfer model VSTAR. We find a best fit abundance of 31 ppmv (-6 + 9 ppmv), which is in agreement with recent results by Bézard et al. 2011 using VEX/SPICAV (R ~ 1700) and contrary to prior results by Bézard et al. 2009 of 44 ppmv (±9 ppmv) using VEX/VIRTIS-M (R ~ 200) data analyses. Comparison studies are made between water vapour abundances determined from the peak of the 1.18 µm window and abundances determined from different water vapour absorption features within the near infrared window. We find that water vapour abundances determined over the peak of the 1.18 µm window results in plots with less scatter than those of the individual water vapour features and that analyses conducted over some individual water vapour features are more sensitive to variation in water vapour than those over the peak of the 1.18 µm window. No evidence for horizontal spatial variations across the night side of the disk are found within the limits of our data with the exception of a possible small decrease in water vapour from the equator to the north pole. We present spectral ratios that show water vapour absorption from within the lowest 4 km of the Venus atmosphere only, and discuss the possible existence of a decreasing water vapour concentration towards the surface.

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Blobrana


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RE: Venus Atmosphere
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A curious cold layer in the atmosphere of Venus

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.
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Blobrana


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Venus' nightglow
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NMSU grad studies Venus' nightglow

Candace Gray spent her childhood with her siblings looking up at the stars and watching for meteor showers. As the recipient of the NASA Earth and Space Science Fellowship, the New Mexico State University graduate student is now keeping her eyes firmly planted on Venus as she tries to determine whether certain oxygen emissions seen in its atmosphere are caused by enhanced solar flux on the planet during solar flares.
Gray has just completed her second year of the graduate program in the Department of Astronomy. Through her proposal to NASA entitled "Upper Atmosphere Chemistry and Nightglow Variability on Venus and its Connection to Solar Flares," Gray believes she can fill some pieces in the evolutionary puzzle of terrestrial planet atmospheres.
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Blobrana


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RE: Venus Atmosphere
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Title: Wind mapping in Venus' upper mesosphere with the IRAM-Plateau de Bure interferometer
Authors: A. Moullet, E. Lellouch, R. Moreno, M. Gurwell, H. Sagawa

The dynamics of the upper mesosphere of Venus (~85-115 km) have been characterised as a combination of a retrograde superrotating zonal wind (RSZ) with a subsolar-to-antisolar flow (SSAS). Numerous mm-wave single-dish observations have been obtained and could directly measure mesospheric line-of-sight winds by mapping Doppler-shifts on CO rotational lines, but their limited spatial resolution makes their interpretation difficult. By using interferometric facilities, one can obtain better resolution on Doppler-shifts maps, allowing in particular to put firmer constraints on the respective contributions of the SSAS and RSZ circulations to the global mesospheric wind field. We report on interferometric observations of the CO(1-0) line obtained with the IRAM-Plateau de Bure interferometer in November 2007 and June 2009, that could map the upper mesosphere dynamics on the morning hemisphere with a very good spatial resolution (3.5-5.5"). All the obtained measurements show, with a remarkably good temporal stability, that the wind globally flows in the (sky) East-West direction, corresponding in the observed geometry either to an unexpected prograde zonal wind or a SSAS flow. A very localized inversion of the wind direction, that could correspond to a RSZ wind, is also repeatedly detected in the night hemisphere. The presence of significant meridional winds is not evidenced. Using models with different combinations of zonal and SSAS winds, we find that the data is best reproduced by a dominant SSAS flow with a maximal velocity at the terminator of ~200 m/s, displaying large diurnal and latitudinal asymmetries, combined with an equatorial RSZ wind of 70-100 m/s, overall indicating a wind-field structure consistent with but much more complex than the usual representation of the mesospheric dynamics.

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