Thursday, November 29, 2007

How Venus got its CO2 atmosphere

Praise goes to Kenneth Chang, for writing the first article on recent Venus discoveries that makes any sense.

We know why Venus is hot -- it's the CO2 atmosphere. The new discoveries are about how Venus went from an atmosphere like ours to a very dense atmosphere that's almost all CO2 ...
New Findings Underscore an Earth-Venus Kinship - New York Times:

... Subsequent visits by spacecraft confirmed that the surface temperatures exceed 800 degrees Fahrenheit, hot enough to melt tin and lead...

... Scientists imagine that Venus formed with much liquid water, just like Earth, but that because it is closer to the Sun, with sunlight twice as intense as on Earth, the water began to evaporate. Water vapor, also a greenhouse gas, trapped heat.

“That heats up the surface and leads to more evaporation,” said David Grinspoon of the Denver Museum of Nature & Science. “It’s a powerful feedback.”

The evaporation accelerated until all the liquid water had turned into a thick atmosphere of water vapor. As the water molecules floated in the air, scientists hypothesize, ultraviolet rays from the Sun broke them apart into hydrogen and oxygen atoms. Chemical reactions with minerals in the rocks transformed the oxygen into carbon dioxide. The hydrogen, the lightest of atoms, escaped into outer space...
So the oceans of Venus, and a chunk of its surfce, turned into an ultra-dense atmosphere of CO2. That's a satisfying story. It will likely help us understand what the habitable zone of star is.

Anyone have a few bazillion tons of hydrogen lying about?

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