Some thoughts on solar-system engineering:

One idea out there is to change the orbit of a good-sized asteroid or comet — about 100 kilometers in diameter — so that it swings by one of the inner planets and then back out to, say, Jupiter. As the cosmic tow truck passes our target planet, it uses its gravitational attraction to tug the planet in the desired direction, then hurtles back to slingshot around Jupiter, picking up more energy in the process. Repeat a few thousand times with a few score asteroids and there you go: Mars in your backyard.

This technique has been proposed as a way to drag Earth away from the ever-brightening sun that otherwise will eventually snuff out life on our planet. It has some downsides, though. One is that each time the asteroid comes by it’ll exert a tidal force ten times greater than the moon’s, wreaking havoc on the oceans and weather. Another is that some Poindexter on the relocation team is bound to make a unit conversion error along the way, and when the asteroid slams into the Earth — well, that’ll be a real pisser. Luckily, we don’t need to worry about things like that if we’re moving Mars or Venus: if we make one planet go boom, we’ve still got a spare.

Once we get the planet where we want it, though, we’ve still got our hands full. However bad the environment on Earth is, Venus’s is worse. Atmospheric pressure is roughly 92 times ours, the planet has no free oxygen or water to speak of, and the surface temp is hot enough to melt lead. Mars has an extremely thin atmosphere but its temperature, while chilly, isn’t so bad, and it’ll get warmer when it’s closer to the sun. That alone might cause enough melting at the Martian poles to release ice-bound CO2 and create a greenhouse effect. If not, we can always try focusing the sun’s rays with orbital mirrors or crashing (smaller) asteroids into the ice.

I don’t see a calculation of what would happen to Venus’ surface temp if it were farther out. Most terraforming plans of either planet don’t generally include moving them to a better location, but it’s worth thinking about — it is, after all, the first three rules of real estate.