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Once styled as Earth's twin, (1) Venus was transformed from a haven for water to a fiery hell by an unstoppable greenhouse effect, according to an investigation by the European Space Agency's (ESA) (2) Venus Express.
Preliminary data from the probe reveal a Venus that is more Earth-like than once thought －－ but not in ways that are reassuring.
"The basic physics of the greenhouse effect are the same on Venus as on Earth," said Venus Express scientist David Grinspoon. "Perhaps the same fate will await the water on Earth."
ESA scientist Hakan Svedhem believes Venus was partially covered with water before it became doomed by global warming. "Probably because Venus was closer to the Sun, the atmosphere was a little bit warmer and you got more water very high up," he told AFP.
As water vapour is a greenhouse gas, this further trapped solar heat, causing the planet to heat up even more. So more surface water evaporated, and eventually dissipated into space. It was a "positive feedback" －－ a vicious circle of self-reinforcing warming which slowly dessicated the planet.
Even today, Earth and Venus have roughly the same amount of CO2. But whereas most of Earth's store remains locked up in the soil, rocks and oceans, on Venus the extreme heat pushed the gas into the air.
Venus Express has detected "whistlers," low-frequency electromagnetic waves that last a fraction of a second and are normally a sure sign of electrical discharges.
"We consider this to be the first definitive evidence of abundant lightning on Venus," said Grinspoon. A powerful source of energy, lightning changes the chemistry of any planet with a dynamic atmosphere, such as Earth or Venus, he added. AFP
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