Mike commented:
> Now, any excess heat a planet radiates above that which it receives from
> the sun is obviously a result of it turning its angular velocity to heat
> through vulcanism in Venus's case (it doesn't have much angular
> velocity, having a retrograde day of some 240 earth days) and through
> convection in the case of Neptune. Unless you think there are Helium3
> people living on Neptune fusing hydrogen for energy...
Actually, the latent heat of planet formation seems to still be
the driver for most of the gas giants (esp. Jupiter). The insulating
layer accumulates relatively fast and the gradual gravitational
contraction produces heat that only slowly escapes. There is
also a fair amount of radioactive material gradually decaying.
I don't think the equations of state are well enough understood
to predict how much heat should be produced by these effects
and the rates at which they should escape through the overlying
material. For example, we can barely make solid-metallic hydrogen,
and can't yet measure such properties as electrical or heat conductivity
effectively). I think the jury is still out on whether Mars does
or does not have a liquid core. And Mars is relatively easy compared
with the gas giants.
But, I would agree the EvMick's quote of Venus radiating 40x its solar
input is higher than anything I've ever seen. Its albedo is very
high, reflecting away much of its incoming light. The high
CO2 concentration in the atmosphere is required to create the
very high surface temperatures. Unless someone is running a
large number of nuclear reactors on the surface, the 40x figure
is dubious.
Robert
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