Venus!

Venus seems like a much better candidate for terraforming. On Venus we don't have problems of 1/100th the air pressure or low gravity(1/8 ours if I remember from scifi movies correctly). Also we have lots of nice CO2 for plants and later on oxygen. How would we thin the atmosphere though?

 

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I don't know that thinning the atmosphere is the whole answer. Beside the runaway greenhouse effect from co2, there is also heavy sulfur compounds. A lot of sulfur compounds turn into things like h2s. A toxic, deadly, colorless gas. It does have a rotten egg smell but only for the first sniff. After that it deadens the olfactory nerves and you don't smell it anymore. However in higher concentrations of around 500+ ppm's it is deadly at the first whiff. It is corrosive, will bind with metals to create mini fractures in the metal and cause metal fatigue relatively quickly in higher concentrations. In addition if there is any water present, sulfur will combine to make sulfuric acid. With co2 and water, carbolic acid, both of which are corrosive. If there is any way to thin the atmosphere it will have to be with some kind of bacteria that can stand the above mentioned compounds. My guess is that you would have to seed the very upper atmosphere with a genetic bacterium especially bred to survive such conditions.
In addition is the rotation problem. Venus keeps the same side to the sun for long periods of time. If I remember correctly. So you also have to deal with one side hot and one cold after the atmosphere is taken care of.

 

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hmmmmmmm........my bad. sulfer issue seems like it could be fixed with some clever genetic engineering. The rotation problem on the other hand is a big problem if you're remembering right.

 

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Well, it's obvious gentlemen:

We must grab Mercury and shoot it at Venus just so that the two merge in a gigantic collision, and the resulting body acquires a fairly rapid spin. This will have many beneficial effects:

1) it will completely destroy the atmosphere, allowing us to re-engineer it from scratch
2) it will melt a great portion of the resulting body; with Mercury being high in metals this should give Venus a sizeable liquid metallic core, which in turn results in a strong protective magnetic field just like Earth's (or even stronger)
3) the resulting body gains rapid rotation, enabling it to maintain reasonable surface temperatures.
4) the collision with Mercury coming from Sun's direction will boost Venus' orbit and put it further away from the Sun, making its ultimate climate less searing (we'd have to be real careful not to make the resulting orbit too eccentric); it also means Venus will be even closer to Earth, making the trips shorter

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The downsides are the technology and the time scale. It would take millions of years for the newly-formed planet to stabilize to the point of becoming colonizable. And it would take propulsive power way beyond current dreams to toss Mercury around like that.

But it'd make a nice plot for a really cheezy sci-fi flick...

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Playing cosmic pool is a dicey thing. If you get it into earth orbital vicinity sooner or later California's earthquake woes will seem trivial. If you get it just right you still don't know for sure for several thousand years. That crossing orbit comet/space rock may come to visit us next orbit around or several orbits thereafter. We simply don't know enough to be doing such yet. I for one would hate to be the next dinosaur species on the block. To increase the rotation of Venus I would propose another tactic. Sling a LARGE asteroid near it. Don't hit it, just swing it by. This orbit, then the next and so on for several hundred years if necessay. Each time you nudge Venus' rotational speed ever so slightly. No mess, no fuss, no suprises. In the end you get whatever you wish if your patient enough. In the meantime you could be dealing the atmospheric problem.

 

I don't know if it's my poor understanding of orbital dynamics or what, but it seems to me that swinging a heavy object by another object will not affect either object's rotation one bit...unless they actually touch. Any tidal interactions would be totally symmetric with respect to approach and departure, thus canceling each other out -- and apart from tidal interactions, what other influence would affect the rotation rates?

 

build your own planet

I believe Boris has a point there, rotation will not be affected if there is only gravitational interation between bodies.
However why would we waste a perfectly good planet like Mercury by smashing it into Venus, lots of debries flying around between Mars en Jupiter to do the trick of speeding up Venus (this would indeed mean a steady bombardment of the planet)
Beside if we are able to take Mercury out of its orbit why not place it simply a little further from the Sun, say in one of the Lagrange points of the Earth Sun system, just to make sure nothing nasty comes flying our way.

Besides if we can do all that, why worry about some stray space debries coming our direction ? If we are that good at playing pool I'm sure we will be able to take the perpertrators to a more safe orbit.

Of course all this is just some childs play, if we really want to build ourselves a suitable home we shouldn't make planets for god's sake ! Those stupid balls of rock are just a waste of materials if one considers that a ball provides the minimal amount of surface for a given volume of matter.
An other thing that we are carelessly tossing away is all that nice energy that comes from our sun, our planet gets about 0.000001 % of the energy that the sun emits and we on our turn reflect 2 thirds of that back into space.
The solution : a Dyson sphere around the sun. The sphere would be something like the size of our planets orbit.
We live on the inside and (if by then we haven't found how to generate artificial gravity) a rotation could provide enough gravity for those living along the equator in a bandwith of say a few million kilometers. This would still mean we would have like a million times the amount of surface we have on earth (including the oceans) to play around on (if we could use the enitre sphere it would even be 100 times more)
It would only take the mass of Jupiter to construct something like it which would be something like 100 m thick, so don't go around digging large holes now, you hear !

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Of course I am assuming a have developped materials that are strong enough to withstand the pressure and which can be tailor made from simple hydrogen. (fuse away I would say)
We could harness all the energy output of the Sun and while we are add it, perhaps tab some mass out of the Sun so it won't burn up that fast. If we are real careful we might have enough energy for the coming 100 billion years to come.

 

Venus

Sometime back, some where I had read the business about the slinging around of a asteroid. However when I went to find it , I didn't. Though I did find something simular. The idea that I did find was to use 2 identical bodies in orbit, 180 degrees apart. The idea was to use the tidal effect over long term to increase the rotation of the planet. Talk about long term... Reputedly this was an overhead conversation between some JPL folks. (heresay)

 

Re: Venus

Yes but this would only work if the planet in question is not cilindrically symmetric around its rotational axis. There must be some irregularity to pull on (sort of speak) since otherwise the added angular momentum of the two would simply cancel out.
Luckaly Venus is just such a planet since the very reason why it has such a low orbit is because of that. The side of Venus that is heavier then the other is faced towards the sun because of this effect, that is the reason why Venus always has the same side towards the sun. The same thing goes for our moon by the way but not for our Earth.
Of course if you want to give Venus more angular moment you will have to fight against the tidal pull of the Sun to do it making it again harder.
Why not give up the idea and us Venus as part of the building blocks to make the Dyson Sphere ?

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I really like Boris' idea!!

...to use Mercury as a projectile...GREAT!