Venus has the problem of spinning the wrong direction though.

Nobody is going to want to live through either those days or those nights

And the bigger problem, that a day lasts 243 earth days.

The only thing venus has, that makes it interesting for human settlements, is earthlike gravity - but the rest is pretty hell like.

To be fair, the gravity thing is pretty hard to fix. You can imagine putting rotating sunshield/mirrors into orbit to fix the day/night/temperature problem, but mass is mass.

The Earth weighs more than everything else between the sun and Jupiter combined, and Venus is 80% of that.

I think Venus gravity is actually fine enough and not in need of fixing. (Old people would probably love it)

But yes, I also see no way of "fixing" the g of mars(which is likely way too low for humans), unless we go into the buisness of planet building.

> which is likely way too low for humans

We don't really have a way to know until we get experimental data (real humans on Mars). Until then, it's all just (un)educated guesses.

"Until then, it's all just (un)educated guesses. "

We know that long time weightlessness causes damage, so 38% of earths gravity will likely have some bad effect, too. This is not just wildly speculating. But yes, for finding out, whether humans still can bear it, we will have to find out and there is no shortage of volunteers.

Hit it with mercury. Get the speed and angle right, and you'll speed up the rotation, increase the gravity, and give it a moon.

Also that would be awesome.

Untill the changed gravity pulls the earth more close or further away from the sun, than we will like. Seriously, the circeling of the planets are interconnected and any big change to that, will have effects on earths year length and distance to the sun. But on the other hand, if we would have the tech to "move" mercury around, we probably could also adjust earths rotation. In either way, this is nothing remotely realistically with current state of the art.

Only on the scale of millions of years.

From the little weight alone under normal circumstances, yes, but when the whole system becomes chaotically unstable, then unpleasant changes can happen fast.

That comes later.

First you want to get your self-replicating probes occupying the Oort cloud, whatever. Get ready to sort and aim. You start with your "rocky" bodies, skipping them off of Venus' atmosphere, just ripping it off in big hunks, until you're down to about one Earth atmosphere.

Next, you flat up drop your icy bodies into Venus, because it really needs water.

During that time you'll want to start constructing your insolation shield, to help cool things down.

Only after that can you move Mercury into place.

I haven't read or watched anything on terraforming Venus in a long time, but isn't a large part of the challenge not just temperature, but the sheer mass of the atmosphere? As in, even if we could cool it, wouldn't that bury the surface under hundreds of meters of dry ice?

Yes. That’s not really a challenge through as it would freeze from the bottom up, unlike water. What is difficult is that it would need to be covered in some sort of insulating material on a global scale before the planet is ever warmed up.

The outgassing CO2 could be captured and turned into carbon and oxygen, with the carbon put to industrial use or into biomass and the oxygen feeding a 400 millibar O2 atmosphere in settlements.

But a sudden volcanic triggered burst of CO2 would be a forever ongoing global risk.

And, as in many sci-fi stories, should those damn Venusians declare war we can just nuke their sun-shield. Servitude guaranteed.

what are you going to do with all the precipitated oceans of sulphuric acid? and then there's the 96% carbon dioxide atmosphere ... that'll take a lot of carbon credits!