Inhospitable Venus was once Earth’s ‘watery’ twin

November 29th, 2007 - 2:00 pm ICT by admin  

Washington, Nov 29: Scientists have come to the conclusion that despite the current uninhabitable environment of Venus, it was once Earth’s twin and even now has some similar traits.
Venus is the second planet from the Sun and is only a few hundred miles smaller in diameter than the third planet, Earth.
The discoveries about Venus having similar characteristics like Earth, mark the first findings from Venus Express, a European Space Agency (ESA) craft launched in November 2005 to investigate Venus.
Observations from the first year of the mission suggest that Venus experiences lightning storms, hurricane-force atmospheric winds, and massive cloud vortexes over both its polar regions.
In addition, the mission team found that Venus, like Earth, has huge areas of circulating air over both its polar regions.
But Venus’s mass of swirling polar clouds forms a double vortex with temperatures much higher than the surrounding area. The warm air may be evidence of a planetary circulation system, with hot air flowing to the poles from equatorial regions.
The ESA spacecraft also provided the first solid evidence for lightning on Venus, according to the study team.
“It’s quite possible there’s as much lightning on Venus as on Earth,” David Grinspoon of the Denver Museum of Nature and Science in Colorado, told National Geographic News.
But in spite of Venus being Earth’s twin in the past, there is no evidence of water on its surface.
“Earth is a water planet, and Venus is its near-twin, so what happened to all the water” on Venus, asked Grinspoon.
A possible explanation for this are the thick, rapidly spinning clouds of Venus, which create a scorching atmosphere with an average temperature of 864degF (462degC) and a surface pressure roughly 90 times that of Earth’s.
Like present-day Earth, Venus could once have been covered in oceans, although the only water there now exists as vapor or as traces dissolved in vast clouds of sulfuric acid.
“On Venus, the processes similar to that of Earth have worked to virtually eliminate water from the planet while maintaining high levels of carbon dioxide, while Earth has retained much of its water and lost most of its atmospheric carbon dioxide,” said Venus Express mission scientist Fred Taylor from the University of Oxford, England.
Scientists suspect Venus’s oceans may have “boiled off” due to a runaway greenhouse effect that saw carbon dioxide levels rise until the gas made up 96.5 percent of the planet’s atmosphere.
Proof of water once existing on the planet’s surface comes from an instrument on the ESA spacecraft known as a plasma analyzer, which showed that the main ions escaping Venus’s atmosphere are oxygen, helium, and hydrogen.
Hydrogen and oxygen ions were shown to be escaping in the same proportions as they are found in water, H2Oproviding a likely mechanism for how water has been leaving Venus.
“If you break up an H2O molecule, the hydrogen and oxygen escape at a proportional rate, so that seems to be where the water’s going,” said Grinspoon.
Further evidence for Venus’s vanished water comes from high levels of atmospheric heavy hydrogen, or deuterium, the study team said.
“As hydrogen escapes, it leaves behind the heavier deuterium, so the amount of deuterium residue is an important clue to the amount of water that’s been lost,” Grinspoon said. “Estimates based on Venus’s levels of deuterium suggest that the planet has lost anywhere from 13 feet (4 meters) of surface water up to an Earth’s ocean’s worth,” he added.
“In the light of the new data, it is possible to construct a scenario in which the climates on Venus and Earth were very similar when they started out, and then evolved to the state we see now, like twins separated at birth,” Taylor said.
“Billions of years ago there is even the possibility that Venus would have been habitable.” (ANI)

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