for National Geographic News
Despite its currently hellish environment, Venus started out much like our own planet and still shows some surprisingly Earthlike traits, scientists announced today.
The discoveries mark the first findings from Venus Express, a European Space Agency (ESA) craft launched in November 2005 to investigate our "sister" planet.
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.
The mission also found evidence as to why Venus turned out more like Earth's "evil twin" despite being similar in size, mass, chemical makeup, and distance from the sun.
"Earth is a water planet, and Venus is its near-twin, so what happened to all the water [on Venus]?" asked team member David Grinspoon of the Denver Museum of Nature and Science in Colorado.
"Fortunately, we now have some clues."
Case of the Missing Water
Venus is the second planet from the sun and is only a few hundred miles smaller in diameter than the third planet, Earth.
But Venus's thick, rapidly spinning clouds create a scorching atmosphere with an average temperature of 864°F (462°C) 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.
(Read "Early Venus Had Oceans, May Have Been Habitable" [October 11, 2007].)
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.
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