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Andre
#3
Jun12-04, 03:03 PM
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P: 5,458
Hi Sage, Yes we have been there.

Assuming that the abundance of elements of both Earth and Venus are comparable, within the same order of magnitude, Earth and Venus should have comparable amounts of carbon in the lithosphere.

The back side of my envellope says that Venus has about the same amount of carbon in the atmosphere as the Earth has in the crust, forming variations of limestone type rox.

The greenhouse hypothesis for Venus (Kasting, Pollack, Ackerman. Icarus. 1984;57:335-55.) assumes that Venus had an Earthlike appareance in the early days including oceans and weathering processes that bonded CO2 to limestone. How get all the limestone of Earth in the atmosphere?

quoting again:
Another runaway effect occurs when high temperature chemical reactions begin to drive carbon dioxide from the rocks into the atmosphere
seems highly inadequate if we need all the CO2 to get out the crust and we need 900-1200 degrees celcius to begin with:

The material needs to reach a temperature of 2,200 degrees Fahrenheit (1,200 degrees Celsius). At 1,650 degrees Fahrenheit (900 degrees Celsius), carbon dioxide (CO2) is driven off, and 2,200 degrees Fahrenheit (1,200 degrees Celsius) is required for the heat to penetrate through to the center of the stone.
http://oikos.com/library/naturalbuilding/lime.html

So I was looking for a chemical specialist who could confirm if the processes are possible under lower temperatures.