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Old 4th July 2010, 10:48 AM   #57
Ziggurat
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Originally Posted by wogoga View Post
Please, try to understand what I've written in my previous posts. I explain the high crust surface temperature of Venus by atmospheric insulation from a colder environment, and therefore the decisive parameter is a form of quantity (mass, thickness), and not pressure of the atmosphere.
The distinction is essentially irrelevant, since atmospheric mass, weight, and surface pressure are all uniquely related to each other on a planet.

Quote:
The -40C can be seen as the temperature of an averaged thermal-emission-surface of Venus (around 70 km above crust surface). The thick atmosphere is able to insulate the more than 450C hot crust surface from this -40C cold radiation-surface.

And now you tell me, that such a -40C radiation-surface could thermally not be as well insulated from a crust surface of 0C, as from a crust surface of more than 450C!
You seem to be having some problems understanding the concept of energy flow. The surface gets some small amount of heating from solar radiation. Even with a small amount of heating, the surface must lose energy to stay at a constant temperature. And it must do so at the same rate that it gains energy from solar radiation. At 450C surface temperature, the surface is able to lose heat to the upper atmosphere largely through convection.

But at 0C surface temperature, convection would stop. The temperature gradient is too small (it needs to meet or exceed the adiabatic lapse rate - that's why the amount of atmosphere matters). Without convection, the surface would lose energy at a much slower rate, slower than it gained energy from solar radiation. So it would not stay at 0C, it would heat up. And in much less time than a million years.
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