Colonizing Mars may sound like a good idea, but it would be a nightmare. Very little atmosphere, no protection from radiation, no natural food, no infrastructure, too little gravity, too cold, no grass, no plants, no lakes, no animal, no skinny-dipping, and almost no way to deal with big problems that will absolutely happen. And you’d have to live underground.
Our bodies are adapted to the Earth’s environment in thousands of ways. Colonizing Mars or anywhere else in our solar system would be disastrous.
What about the concern that some disaster could happen to the Earth that would destroy humanity?
I think that within 100 years or so, we’ll have the technology to avoid large asteroid collisions, devastating diseases, super-volcanoes, etc. So after a century or so, I think it’s highly unlikely that any disaster would destroy humanity. (Astrophysicists think the Sun will serve us well for at least a billion years).
World population is expected to top out at less than 10 billion people, and with proper recycling, there are plenty of resources for all. After all, our natural resources do not get used up. (The exceptions are the fossil fuels, but we won’t need them after this century). There is the same amount of iron, aluminum, chromium, and all the other elements, that there were millennia ago.
As far as extra-solar planets, keep dreaming. The planet, Proxima Centauri, is in the nearest star system to our own solar system. And it’s over 4 light years away. At the current speeds of our spacecraft, it would take tens of thousands of years to get there. It would be a miracle if, next century, we could get there in a thousand years.
It would be more of a miracle if we could get there with anyone alive.
What about small, robotic spacecraft? By next century, it's possible but not likely, that we’ll probably be able to send out a bunch of these to various star systems. Once one gets to a planet that it can land on, it could send a transmission back to Earth about what it has found. It can then duplicate itself, and send out more small spaceships. I’ve seen some estimates that we could have these essentially visit every part of our galaxy in 100,000 to 1,000,000 years. A million years seems like a long time, but hominids were around a million years ago. And the dinosaurs died off over 60 million years ago. So it really isn’t as long as it sounds. And we’d know for sure which planets, if any, have intelligent life.
But human colonization of extra-solar planets? We’d need a spaceship to house hundreds of mostly young couples, that can support them for many generations. If you think that’s going to work, you’ve been watching way too many Star Trek and Star Wars’ movies. I know I have.
Our only hope is that Elon Musk develops a huge Tesla spacecraft that can travel at ‘ludicrous speed’. Hopefully, we wouldn’t run into a bunch of Klingons.