Expert: Philip Stahl - 8/19/2011

Question
Hi,

If the planet Venus had had the same type of atmosphere as Earth, so never any greenhouse effect, what would its average global temperature be at this stage of time compared to the Earth, given its distance from the Sun? Would snow/ice be possible at the Venusian poles in such a situation? Also, what would the effect of Venus' unusual rotation have on the weather etc. in such a situation? Would the 0.8G(?) gravity be deleterious to human colonists other than slight loss of muscle-mass? I suppose, though all colonists would have to do is always carry around suits/backpacks etc. which weighed at least 25 percent of their body-weight...

I'm interested in the notion of terraforming, which is why I'm asking all this. Thanks.

Geoff

Answer
Hello,

This is an intriguing question, especially since as a purely hypothetical one we'll never know if the real Venus can be terraformed.

Starting out from your assumptions, one needs to examine at least the one major factor that would alter (from Earth's conditions) and that is the solar constant. At Earth it is around 1360 W/m^2 but from Venus (estimated using a mean distance from the Sun of 0.72 AU) one would find it at nearly 2600 W/m^2 - or nearly double.

IN other words, you'd still have seriously hot temperatures, over most of the planet, but not in the range we behold with Venus incipient greenhouse effect (featuring temperatures hot enough to melt lead!). It's hard to say but I suspect the highest temperatures would be somewhere just under the boiling pt. of water. Maybe 190F.

I can't see that Venus rotation would have much an effect - if any- on its weather. Indeed, since Venus rotates about 243 times more slowly than Earth you're not going to get much of a Coriolis force, so I wouldn't expect much in the way of storms. (Say like hurricanes on Earth).

As for the surface gravity (Venus' by the way is at 0.91g, not 0.8g) I don't see that as any problem for hypothetical terraformers. Even a 165 lb. explorer carrying a 25 lb. pack would only feel like 173 lbs. there, as opposed to 190 lbs. on Earth.

So, no biggie!