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Greenhouse Effect on Venus

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Venus is nearly a twin to Earth in size. However, it has atmospheric pressure on the surface 90 times that of Earth. The temperature on the surface of Venus may be as high as 900 degrees Fahrenheit.

Scientists already had a runaway-greenhouse explanation in which water existed on Venus, but only as vapor. In a greenhouse effect, Sun heat is trapped by gases in a planet's dense atmosphere.

A NASA Image of the Planet Venus
The wet-greenhouse and the runaway-greenhouse theories have a greenhouse effect in common.

In the runaway-greenhouse explanation, Venus was said to be so hot that its water existed only as vapor and had no chance to condense to liquid on the surface. Water vapor rose into the atmosphere, where radiation from the Sun cracked it into separate oxygen and hydrogen atoms. The hydrogen escaped into space and water couldn't form.

But the Ames researchers, looking at different climates on Venus, Earth and Mars, didn't like the runaway-greenhouse explanation. That old theory forgot that the Sun was 25 to 30 percent cooler 4.5 billion years ago. It also did not account for the water loss.

Is Earth A Greenhouse? The wet-greenhouse theory might be a model for Earth. Scientists are concerned that burning fossil fuels puts too much carbon dioxide into Earth's air, causing the atmosphere to trap heat from the Sun. That could raise air temperatures gradually, increasing sea levels as polar ice melts.

However, Earth is farther from the Sun and has a different atmosphere which is expected to prevent the climate catastrophe that turned Venus into a desert.

NASA scientists have bounced radar waves off cloud-shrouded Venus and detected colossal highly-reflective blobs and rings that may be lava flows or volcano crater rims rich in fool's gold.

The radar survey by researchers from NASA's Jet Propulsion Laboratory (JPL), Pasadena, California, turned up more evidence that volcanoes have erupted on Venus within the last few million years, maybe even within recent centuries.

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