I do not think building a city on Mars is going to solve anything at all! First of all, it’s unlikely a city on Mars will be built due to the incredible problem of transporting parts and materials to that planet. We all would like this to happen, since we screwed this planet, to go to a new planet. However, Mars has such an inhospitable climate that you wouldn’t be able to go outside without exposure risk of harmful UV light and cosmic radiation. These things give you cancer. There’s neither an organized magnetic field not an atmosphere (well, technically there’s an atmosphere 100 times weaker than our own. What’s left is poisonous to us.) Without an organized magnetic field there’s no aurora borealis to protect you by drawing off the sun’s harmful rays.
It is most probable, at the present moment, that China will put some humans on Mars by 2020,.
They will likely beat all the other countries and private companies with similar aspirations.
However, Mars will never be able to support permanent settlements due to extreme radiation, poisonous air, and dead soil.
Well, Earth has an eccentric orbit and Mars has too. That means neither planet has a perfectly circular orbit around the sun, so it’s complicated. In 2016 we were fairly close. Mars was a mere 46.8 million miles away.
We can’t even alter Earth’s atmosphere to make it more suitable or to stop global warming, what to speak of Mars.
Sadly, the idea of terraforming Mars is mostly science fiction, not real. Mars is a dead planet. Even if we could somehow get a breathable atmosphere there, because there is no organized magnetic field it would blow away and there would never be protection against dangerous UV light from the sun.
Mars is not inhabitable for long-term human presence.
I’m going to suggest if we could terraform Earth to be a sustainable, livable planet, that would be the best use of our technology, since we’re already here. It would also prove we could do it elsewhere. Why go to Mars, Venus the Moon or Mercury when you could figure out how to take all the toxins and poisons out of our own air here on Earth?
Think about it.
You know why we don’t? Because we can’t. It’s all a scam.
We should never, ever try to terraform. This is a bad idea. We need to keep these planets in a pristine condition as we can in order to study them for the possibility of life having once existed on them.
This is also NASA’s official position. Do not contaminate other planets, and don’t contaminate Earth on return.
In my opinion, hopefully neither place because there is no valuable reason for humans other than our robots to establish a presence in either place. Robots are expendable and you don’t have to bring them back. They can transmit what they find. Both are dead planets. Both have no reason to settle there.