* Astronomy

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RE: Venus

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On this day at 14:28 UT, 1959, the planet Venus occulted the star Regulus. The occultation was used to determine the diameter of Venus and the structure of the Venusian atmosphere.

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Was Venus once a habitable planet?

ESA's Venus Express is helping planetary scientists investigate whether Venus once had oceans. If it did, it may even have begun its existence as a habitable planet similar to Earth.
These days, Earth and Venus seem completely different. Earth is a lush, clement world teeming with life, whilst Venus is hellish, its surface roasting at temperatures higher than those of a kitchen oven.
But underneath it all the two planets share a number of striking similarities. They are nearly identical in size and now, thanks to ESA's Venus Express orbiter, planetary scientists are seeing other similarities too.
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The International Astronomical Union (IAU) has approved the name Nancy for a 4.4-km-wide crater on Venus located at 6.4°N, 272.2°E.

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Title: Superrotation on Venus: Driven By Waves Generated By Dissipation of the Transterminator Flow
Authors: Hector Javier Durand-Manterola, Deni Tanibe Zenteno-Gomez, Hector Perez-de-Tejada

Context: The superrotation phenomenon in the atmosphere on Venus has been known since the late 60's. But until now no mechanism proposed has satisfactorily explained this phenomenon. Objective: The aim of this research is to propose a mechanism, until now never considered, which could drive the atmosphere of Venus in its superrotation. This mechanism involves the transfer of the transterminator ionospheric flow momentum to the lower atmosphere via pressure waves generated in the cryosphere of Venus. The mechanism proposed presents a source of energy sufficiently strong to allow the transfer of energy despite dissipation. Method: The energy flow which transports the transterminator flow and the energy lost by the viscosity in the superrotating atmosphere were calculated. Both results were compared to establish if there is sufficient energy in the transterminator flow to drive the superrotation. Finally, the amplitude that the waves should have to be able to obtain the momentum necessary to induce superrotation was calculated. Also an experimental model was made presenting some similarities with the process described. Results: The calculated power for the transterminator flow is 8.48x10e10 W. The calculated viscous dissipation of the superrotating flow is 1.4x10e9 W. Therefore, there is sufficient energy in the transterminator flow to maintain superrotation. The amplitude of the waves generated in the cryosphere, necessary to deposit the power dissipated by the viscous forces, is 10e-4 m for waves of 1 Hz and 10e-8 m for waves of 10e4 Hz. These amplitudes imply that at the altitude of the clouds on the night side there must be a constant sound of 83 dB. If the superrotation of Venus were to stop, with the continuous injection of 1.4x10e9 W, the actual superrotation would appear again in 1.4x10e6 years.

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Title: Oxidation of CO on surface hematite in high CO2 atmospheres
Authors: John Lee Grenfell, Joachim W. Stock, A. Beate C. Patzer, Stefanie Gebauer, Heike Rauer

We propose a mechanism for the oxidation of gaseous CO into CO2 occurring on the surface mineral hematite (Fe2O3(s)) in hot, CO2-rich planetary atmospheres, such as Venus. This mechanism is likely to constitute an important source of tropospheric CO2 on Venus and could at least partly address the CO2 stability problem in Venus' stratosphere, since our results suggest that atmospheric CO2 is produced from CO oxidation via surface hematite at a rate of 0.4 Petagrammes (Pg) CO2 per (Earth) year on Venus which is about 45% of the mass loss of CO2 via photolysis in the Venusian stratosphere. We also investigated CO oxidation via the hematite mechanism for a range of planetary scenarios and found that modern Earth and Mars are probably too cold for the mechanism to be important because the rate-limiting step, involving CO(g) reacting onto the hematite surface, proceeds much slower at lower temperatures. The mechanism may feature on extrasolar planets such as Gliese 581c or CoRoT-7b assuming they can maintain solid surface hematite which e.g. starts to melt above about 1200K. The mechanism may also be important for hot Hadean-type environments and for the emerging class of hot Super-Earths with planetary surface temperatures between about 600-900K.

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Artemis, Venus: The largest tectonomagmatic feature in the solar system?

New geologic mapping reveals that Artemis, a unique 2400-km-diameter feature on Venus, is much larger than previously recognised, including a wide outer trough (>5000 km diameter), a radial dike swarm (12,000 km diameter), and a concentric wrinkle ridge suite (13,000 km diameter). Artemis's evolution included formation of its interior and chasma, accompanied by lateral propagation of radial dikes. The escape of dike magma to the surface formed local cover deposits that buried parts of the remaining radial fracture suite. Cover deposits are cut, in turn, by wrinkle ridges that likely formed by coupling of convective mantle flow with the lithosphere. The outer trough formed late relative to radial fractures, cover deposits, and wrinkle ridges. We suggest that Artemis represents the magmatic signature of a deep mantle plume acting on relatively thin lithosphere. As such, it appears to represent the largest tectonomagmatic feature in the solar system. The newly recognised vast extent of Artemis holds implications for the formation of giant radial dike swarms, wrinkle ridge formation, terrestrial planet mantle-lithosphere coupling, and Venus's surface and geodynamic evolution.
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Volcanic Venus

Scientists have detected for the first time recent volcanic activity on Venus, the planet that is the most similar to Earth in terms of mass and density, but that has a surface temperature hot enough to melt lead.
Knowing that Venus is volcanically active could shed light on the mysterious geological history of Earth's sister planet, which does not have plate tectonics, meaning the planet's surface does not evolve through a process of rigid plates slowly shifting across the underlying mantle. Because the runaway greenhouse effect, or the phenomenon that occurs when a planet absorbs more energy from the sun than it can radiate back, was first discovered on Venus, this finding could also lead to a better understanding of climate change in general and, more specifically, how gas emitted from volcanoes may affect a planet's atmosphere.
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NASA-Funded Research Suggests Venus is Geologically Alive

For the first time, scientists have detected clear signs of recent lava flows on the surface of Venus.
The observations reveal that volcanoes on Venus appeared to erupt between a few hundred years to 2.5 million years ago. This suggests the planet may still be geologically active, making Venus one of the few worlds in our solar system that has been volcanically active within the last 3 million years.
The evidence comes from the European Space Agency's Venus Express mission, which has been in orbit around the planet since April 2006. The science results were laid over topographic data from NASA's Magellan spacecraft. Magellan radar-mapped 98 percent of the surface and collected high-resolution gravity data while orbiting Venus from 1990 to 1994.
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