It's not that simple. Even if we did manage to "restart it" with nukes, we couldn't keep it going. What keeps the Earth's core going is simply the presence of our moon. The gravitational pull from it keeps the core active, which produces our magnetic field. And I doubt very much if we'd even have enough nukes to do the job. They're not quite as powerful as people seem to think.
I don't think the Moon has too terribly much to do with Earth's partially molten core actually. I think it has more to do with the fact that Earth is a very large, dense planet and our core itself is over-sized relative to the planet, which is likely a product of the collision that gave us the moon. The theory goes that the core of Theia (the hypothetical mars-sized planet that crashed into early Earth and gave birth to the moon) basically merged with Earth's, which gave the Earth a huge core, while the Moon basically got very little core material and lots of crustal material, which is why it's core is relatively small.
So basically, the Earth has a big core, which got a massive energy boost from the collision, which, coupled with lots of radioactive heavy metals, has kept it partially molten to the present day.
Except we don't have the technology to build floating cities, we need solid ground. And a 400C degree surface temperature kind of puts a damper on that idea. Right now, Mars is much more viable as far as building a sustainable colony than Venus. While it might be possible to do so in the future, it will require far too many resources and technological ability than we currently possess.
I agree and I think Metatron is seriously understating the difficulty of floating Venusian cities. We have 0 experience with that but lots of experience building stuff in harsh environments on the ground or under it. Big difference there.
I don't know that it's a better candidate, since we have no idea how to practically begin terraforming. The magnetic field is a much bigger problem than the atmosphere (which is a huge problem, but again, we're talking about terraforming here, dealing with atmospheres is something to be assumed) because how would you restart or induce an internal dynamo? Yeah, Venus has a small one, but it's produced mostly from interactions between the ionosphere and the solar wind, rather than by internal convection like the Earth's. But the honest truth is that we know so shockingly little about Venus beneath its clouds, so we really don't know what's happened to its core.
Mars, on the other hand, we are pretty sure has a solidified core.
The lack of a magnetic field is a serious, but very long term problem. In the short term, you really don't have to worry about the solar wind stripping any atmosphere we put on Mars as it would take thousands, if not millions of years, for any losses to be appreciable. In any case, we could replenish the losses much faster than they could be stripped.
I have a NASA design study from the 70's about a giant space station colony that would require lots of lunar mining to support. Part of the study delved into the effects that large scale mining, construction and spacecraft launches would have on the lunar environment. It turns out that just a few largish factories and a bunch of rocket launches would actually give the moon an appreciable atmosphere (though not one you'd want to breathe) - compared to the amount of industrial outgassing that goes on here on Earth, it would be really easy to give the moon an atmosphere. They also explained that even with the low lunar gravity and complete lack of magnetic field, it would take hundreds of years for this atmosphere to dissipate if all construction/rocket launches stopped.
So extrapolating a bit, keeping an atmosphere on Mars wouldn't be as insurmountable a challenge as giving it an atmosphere in the first place.
Even if they were, they'd be useless given that burning them actually requires oxygen, which you'd have to produce. But Mars likely has deposits of metals and other stuff that you need to build a civilization at reasonable cost (space-age wise).
I've said it a million times and I'll say it again - colonising Mars is not a matter of "what's there that's valuable". The answer to that question is nothing, nothing that would make it profitable. Mars will be colonised for what can be there once it is developed.
Humans on Earth expanded into some pretty inhospitable places (extreme polar regions, deserts, high mountains) and they clearly didn't go there because it was better than the other places - they went there because they could.
I once tried to argue against this with you but you are absolutely right. Apart from scientific discoveries, there is very few things valuable enough on Mars worth the expense of exporting back to Earth (aside from novelty 'Made on Mars' items with millions for sheer novelty). The asteroids are different given the relative easy of exporting materials back from them.
I actually hadn't considered Venus as harboring life. I was speaking about utility to us. I think Mars is more likely, or one of the Galilean moons, because any water there is likely to be subterranean, where things like radiation would not be nearly the problem they are on the surface.
I am not 100% sold that water is absolutely necessary for life. For Earth life, yes, it is. But we have such a small sample size of types of life (basically only Earth life). So I think it could be possible to have life without water, but it would be obviously very different. And there is all kinds of interesting chemistry that could happen on Venus but not on Mars due to the large, active and energetic atmosphere. I think ready access to energy is more important to life than water honestly, but I'm probably wrong.
But as you say, we know next to nothing about Venus but a great deal about Mars.
Genetic engineering would indeed be needed, but I doubt we've got the necessary skills right now. I mean, the changes to the DNA of Earth-based organisms would have to be massive. We'd probably start with the things that manage to survive in Antarctica or Atacama desert.
It would require massive changes to DNA of organisms, but really, once we've figured out how to
fundamentally change organisms (which we are on the cusp of) would it be really that much harder to make lots of changes?
Those Martians know what they did, and they are going to get what they deserved. Humanity #1!
Your joke is funny, but I was completely serious. *IF* life is found on Mars, it begs a serious question - do we have the right to change Mars such that it is more compatible for Earth life if it kills the native Martian bacteria or whatever?
I think so, because a) Frak em and b) Mars life is probably not very plentiful and Earth life is and we depend on Earth life and if we can spread it around, that's probably better in the long run for all life in the universe than preserving a handful of microbes that can only exist in very specialized environments.
I guess the Earth itself is a specialized environment itself, but Earth life is extraordinarily diverse and plentiful and spreading it around the cosmos is preferable in the long run to preserving a few motes scratching by on Mars.
I'd love to live long enough to see the first kid born on Mars, grow up, and then come here and be crushed by superior Earth gravity.
I think we'll be modifying our children to cope with Martian gravity such that they keep sturdy bones despite the low gravity.
