I caught myself wondering this question the other day.
"What happens if a meteor comes and strikes Earth, and blows it all up to fuck? Where will we go?"
We have 3 (un)realistic options.
Option 1: The Moon
The moon is probably the best choice. This is because it's pretty close to Earth. It's 384,400 km away.
Being close to Earth also means that it also has a similar temperature to Earth. Or it would do, if it wasn't for the fact that it has knack-all atmosphere.
Gravity and Atmosphere
It is small, so it has very low gravity (1.62m/s^2). This means it can't really hold onto a lot of gas to create an atmosphere. It also has no magnetosphere, so it can't deflect solar wind. Solar wind is pretty harmful and will fuck you up. The low gravity is also harmful to our health - loss of bone density, fluids not pooling where they should.
Water and Soil
It doesn't have much in the way of water. Plants can't grow on its surface, and if you try to take your helmet off outside, you'll die. If we're going to live here, it has to be in some air sealed habitation dome or something.
Verdict: It's a shit place to live.
Option 2: Mars
Mars is the next best choice. It's actually a planet! That means it's bigger than the Moon. It should at least have some decent gravity then.
It's much further from Earth than the Moon, at 225 million km away. It'll take fuckin ages to get there. Hence why no-one's been yet. In the instance where we have to flee to somewhere, this is a big factor. Mars is also further away from the Sun than Earth, so its temperatures are lower. It's still just about in the habitable zone.
Gravity and Atmosphere
Mars has gravity, but not loads (3.73m/s^2). Humans may be okay here, but it's still not exactly what our bodies are made for.
Mars has no magnetosphere. This is Mars' big problem. It's big enough to have a shit-ass atmosphere, but because it has no magnetosphere, the Sun can blast it away with cosmic rays and that leaves no real atmosphere.
Forget breathing with no helmet. Plants are also not going to grow in that.
Water and Soil
It appears to have a bit of water on the poles though, so that's something. Ice, so it will need processing rather than us being able to tap into the local water table like here.
The soil is also not suitable. This was a plot point in The Martian movie lol. You could probably turn poop into fertiliser, but this and the air issue mean there will be no plants outside.
It has an epic mountain? That's cool, I guess. Hopefully we can have windows in our habitation dome to look at it.
Verdict: It's a shit place to live. Also fuck flying there, it's far.
Option 3: Venus
Venus is remarkably similar to Earth! It's almost the same size! It's closer to the Sun as well, so it's definitely warm enough (lol).
Gravity and Atmosphere
Its gravity is 8,87m/s^2, so that should be easier for our bodies to adapt to.
It has barely any magnetosphere, so the same old blasting with solar wind. It has lots of clouds, though, which may insulate surface dwellers from radiation.
However, it has far too many clouds. Its atmosphere is far thicker than Earth's, and is mainly made of CO2, so this means it has a surface pressure of 92 bar (92 times that of Earth) and it causes a horrific surface temperature. And then the CO2 facilitates the formation of acid rain, so existing on Venus' surface is straight up not going to happen.
You might get away with floating a cloud city on its CO2 clouds, though. It'll need to be shielded from radiation. Also, don't fall off.
Water and Soil
No. No-one is going to live on the surface. It's not going to happen. Russia sent a bunch of probes that landed on it and they lasted from 23 minutes to two hours.
Verdict: It's a shit place to live.
Author's note: I feel a bit sad about Venus because it's like an alternate reality Earth where something went wrong. It could be fixed! All we need is to:
- Get it to spin at a similar rate to Earth
- Clean up that CO2
- Get some plants down there to create a breathable atmosphere
Simple (lol)
So then, what?
I didn't put any other places because we haven't even made it to Mars yet, so we're definitely not going to Europa or any other candidate. Places like Mercury are even less realistic.
If Earth stops being habitable, we're in big trouble lol. Luckily: the odds of a cataclysmic meteor strike is pretty fuckin small, even astronomically. And if it does happen, well... it's game over. Can't really stress about that. See you next mission? Haha
Tobio