Best evidence of active lava flows spotted on Venus
ESA's Venus Express spacecraft has found the best evidence yet of active lava flows on Venus. Earlier missions to Venus have shown that the surface bears the unmistakable scarring of fierce, ancient volcanic activity. However, prior to Venus express, no mission had been successful in directly imaging clues to contemporary volcanism. This quirk has baffled scientists for years, as it has long been assumed that Venus hosts an internal heat source, and that heat has to escape somehow.
Venus is often given the moniker "Earth's twin", owing to the fact that it possesses a similar mass and composition to our planet. In reality, the landscape of Venus is scarred and barren, cloaked in a thick, toxic atmosphere that has created a runaway greenhouse effect resulting in a surface temperature of 462° C (864° F).
Previous observations of Venus' atmosphere have obliquely hinted at the presence of active volcanism. For example, a spike in sulphur dioxide levels in Venus' upper atmosphere between 2006 and 2007 seemed to suggest a fierce but brief bout of volcanic activity, the after effects of which gradually subsided over the following five years.
One of the key impediments to our understanding of Venus is the dense nature of its atmosphere, which makes direct observation of the surface all but impossible. ESA's Venus Express was able to pierce the atmosphere and probe the surface of Earth's hellish twin by imaging in the infrared spectrum using its Venus Monitoring Camera (VMC).
Data returned from theVMC recorded a number of incidents in which the surface temporarily brightened and subsided over the period of just a few days along the Ganiki Chasma rift. The region sits close to the volcanoes Ozza Monsand Maat Mons, indicating that the events may have been volcanic in nature.
"We have now seen several events where a spot on the surface suddenly gets much hotter, and then cools down again," states Eugene Shalygin of the MaxPlanck Institute for Solar System Research, Germany, and lead author of the paper on the findings. "These four ‘hotspots’ are located in what are known from radar imagery to be tectonic rift zones, but this is the first time we have detected that they are hot and changing in temperature from day to day. It is the most tantalising evidence yet for active volcanism."
A paper regarding the findings is available in the journal Geophysical Research Letters.
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Of course, the fact that it's 25 *million* miles closer to the sun has nothing to do with it...
1. Greenhouse effect would be observable only if the atmosphere were motionless, so heat exchange between the surface and outer space would be possible only by heat radiation. But in reality, the atmosphere of a planet always has a strong wind system, because of Sun's nonuniform heating effect and planet's rotation. So, there are always strong vertical streams, conveying heat between lower and higher parts of the atmosphere. Evaporation and precipitation also act as strong vertical heat transfer. Hence, there is no way to observe the greenhouse effect in a planet's atmosphere, because vertical streams always carry away the accumulated heat.
2. The high surface temperature of a planet is simply the result of adiabatic warm-up of the gases. The outer temperature of the atmosphere is determined by the avarage space temperature (an average of Sun's radiation and the space cold). But when vertical streams bring down the cold outer gases of the atmosphere to the planet's surface, the gases are compressed by the atmospheric pressure, and the gases will warm up. Hence, the surface temperature is basically determined by the outer average temperature and the pressure of the atmosphere. Our atmosphere is relatively low-pressure, so our planet's surface temperature is not too high. The pressure of the atmosphere on Venus is 92 bar, so the adiabatic heatup is much higher, than on Earth.
The atmosphere has 93 times the mass as Earth. At 1 bar (equal to Earth Sea Level) of pressure, or about 30 miles up, the temperature is equal to Earth average. It is an affect of air density.