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Tuesday, July 3, 2012

Back to Venus

Anytime you mention something about the Green House Effect doesn't consider something, Venus gets thrown in your face.  I don't live on Venus.  I don't plan to vacation on Venus.  I personally don't care much about Venus, but Venus is the poster planet for the Green House Effect.

Since I propose that Venus' inhospitable surface temperature is mainly due to geothermal energy and conduction, I get labeled as an idiot, because everyone knows that Venus is only hot because of the Green House Effect.  HORSE HOCKEY! I says.

Once more, the surface of Venus has a radiant energy of around 13,600Wm-2 and only a few milliwatts of geothermal energy estimated by a variety of models.  I don't dispute that, personally I do think it is a little higher, but that is close enough for me.  So let's say Venus has 50 Milliwatts of geothermal energy average leaking out of is volcanic sores.  The surface is so hot and the atmospheric pressure so high, that volcanoes can't erupt, they can just ooze.

I would imagine that in its past, Venus had a crap load of volcanic activity.  Hell at one time it was probably nothing but a ball of lava.  Then the net geothermal flux was probably a touch higher than 50 milliwatts.  In order for the geothermal to reduce to 50milliwatts, the surface had to arrive at some equilibrium with the atmosphere.  Since the surface radiant energy is 13,600Wm-2 and the atmosphere about 90 times heavier than Earth, then the energy of the surface and the atmosphere have to be close to equal.

Now the popular theory is that CO2 ran away in a green house effect and caused the hot surface temperature.  Well, since geothermal energy is positive, I reckon the green house effect mush have caused the geothermal energy.  Weird logic huh?  That is because it is weird, that's the problem with the green house theory.

With the Venusian landscape of oozing volcano whannabees, geothermal energy over time was transferred to the atmosphere where is became potential energy.  It expanded the atmosphere against gravity.  I have no doubt that the Green House Effect played some role, but it would not be the only player.  Since a Venus day is awfully long, about 2800 hours and is surface wind speed about 2 meters per second, it would be kinda hard for the solar energy captured by the Green House Effect to cause the Venusian atmosphere to become isothermal and build enough potential energy to expand the atmosphere.

Venus is about the same size as Earth so its gravity is about the same as Earth.  It atmosphere is about 90 times more dense so its surface pressure would be about 90 times as much.  So it would take about 90 times as much energy flowing in a steady state to raise that atmosphere.  Since the planet rotates so slowly, it would take roughly 4 times the Earth energy to make up for the slower rotation or a total in the ballpark of 360 times energy transferred into Earth's atmosphere.  That is only 360 times 188Wm-2 or 67,000Wm-2 of solar input energy or combination of solar and Green House Effect energy containment to inflate the friggin' atmosphere.  Once inflated, it just takes a steady flow to maintain.  That flow would be about 13,600Wm-2 at the surface that would reduce to zero while the energy is converted into potential energy to keep the atmosphere inflated.

So I don't get into Venus' Green House Effect much, because it doesn't explain how the atmosphere got there, at least to my satisfaction.

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