Space/Science — HabitableZone

Space/Science » in reply to re: What else can I call it?

Effective temperature
Adam — (archived)

Hi gb

Venus's atmosphere contains a lot of heat - its average temperature (from top to bottom) is about 630 K and there's over 1000 tons of gas per square metre. In all about 500 gigajoules of heat. At the top of the atmosphere it only radiates at ~ 232 K, so the heat loss rate is a miniscule 164 W - thus the characteristic time is ~97 years. And that's not factoring in the warmth in the regolith or any adsorbed gas or still hot lava plains. In all the place would take several centuries to freeze out the CO2 without artificial help - an important brake on terraforming efforts. To freeze out the nitrogen would take millennia since the rate of heat-loss declines with the 4th power of the effective temperature.

Earth's atmosphere is at an average temperature of about 260 K, masses 10 tons and is radiating at about 240 W - meaning its characteristic time is just 125 days. So atmospheric freeze-out might take a few years. Chill down to equilibrium with Earth's heat-flow would take decades.

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