If we could shade Venus from the sun, how long would it take to cool down to Earth-like temperatures?

Question

And what about water? How to get it there?

Answer 1

Water exists on Venus already, in the clouds.
More could be transported there by asteroids and comets.

The temperature could not be lowered quickly. Small bodies in the solar system, asteroids, cool at rates of 1 degree per thousand to 1 million years depending on their mass and distance from the sun.

Venus' Atmosphere is not as dense as a solid asteroid, but it is comparably massive and closer to the Sun.

In order for a large sunscreen to work, it would have to be locked in a stable orbit at the Lagrange point L1 of the Venus-Sun system. At a distance from Venus in the area of several million miles, the shade would have to be planetary in size, thousands of kilometers across.

teh best plan would be finding a way to strip the atmosphere off the planet completely, that would create a "sunny side" temperature of 200 degrees Celcius while close to absolute zero on teh unlit side.

Venus rotates only every 244 days or so, so the temperatures will not even out much.

then you could rebuild the atmosphere with comets or asteroid impacts until you get the desired mix.

Answer 2

It would probably take quite a while. The heat-holding capacity of the planet and its atmosphere must be very large.

A better idea might be to move Venus. Move it out as far as the Earth (put it opposite us in our orbit, so we don't interfere with each other) and then put Mars in orbit around Venus like Earth has its Moon.

What will happen is, not only will Venus be cooler, Mars will strip away some of the atmosphere due to its own gravity! As a result, the gasses (mostly sufur dioxide, IIRC) will condense and we can begin to terraform both Mars and Venus. By the time we really need to do it, I guess we will have the technology to do it.

BTW, read The Martian Way, a classic stroy of getting water from the astroid belt to mars, in the form of artifical comets. Again, by the time we need to do it, we will be able to do it.

As far as shades, something like a disk of aluminum foil would work for a little while. A comet steered into a circular orbit inside the orbit of Venus would evaporate and form a cloud; I don't know whether that would last any longe than tinfoil. Perhaps best of all, how about a big diverging lens, which would reduce the amount of insolation the planet would receive...?

Of course, if the Sun flares up (as we have evidence of it doing in the past) all bets are off: check out the Moon rocks in the Smithsonian. They show signs of having been heated until the glazed on their top side, like pottery glazing in a kiln. That is about four times as hot as the Sun normally gets. On Earth, the oceans must have boiled, and that is probably what caused Noah's flood, not to mention condensing and precipitating to form glaciers and polar icecaps. [For more information on this topic, please refer to one of my previous best answers on a question regarding global warming.]

26 OCT 06, 2330 hrs.

Answer 3

A hell of a long time I would guess. It took Earth billions of years to cool down....but then again Venus doesn't have Earth's type of atmosphere....
How to get water to Venus? Find a way to synthesize it or just bring a ton from Earth, I guess.

Answer 4

First figure out how to shade Venus from the sun, then ask that question.

Answer 5

10 points for most hypothetical and unrealistic, but the imagination is good. The water is there. If you could cool the planet, it would condense out of the atmosphere. That would take centuries or longer.

Answer 6

Absolutely false. The earth has been cooling since 1998. The only way to say it has continued warming is to manipulate data. In 1976 we were "headed for a new ice age by 1990". That failed to happen. In 1989 we were "headed for global warming which will cause droubt and famine worldwide by 2000." That failed to happen. In 2006 it changed to "climate change". Now any change in temp or precipitation is caused by "climate change" which is "man made. Truth is its complete hogwash. Its a computer model that lacks the necessary data to project the weather 1 week from now much less 20 years from now.