I know my answers to these kind of questions aren’t popular, but they are the truth. Many do not want to hear the truth. We are absolutely convinced mankind is going to colonize Mars and beyond.
Your question, for example, is what is called a “leading question.” No matter how it’s answered, “Five years, ten years, 50 years,” it means Mars is getting colonized sooner or later. It’s like asking a man on the witness stand, “Mr. Doe, when was the last time you beat your wife?” No matter what he answers, he’s admitting guilt. That’s a leading question.
The truth is Mars will not be colonized by anyone. Ever. So if you don’t like to hear that, don’t read any further. For the rest of you, I’ll briefly explain why I say so below.
I’ll admit there’s an improbably small possibility someone may go to walk on Mars for no other reason than to say we went to Mars. Whether that happens or not will have to be seen. However, if it does happen, getting that person or persons to Mars will be extremely dangerous, keeping them alive on Mars equally difficult, and getting them back almost impossible. They will likely die up there, and they know it.
People are actually signing up for one way trips because they know they won’t be coming back.
Sending robots, rovers and orbiters to Mars is much less expensive and much safer than sending people, and there is nothing a person could do up there that a machine could not. For that reason there is no scientific value to risking human lives to walk on Mars, let alone “colonize it.”
The Mars atmosphere is too thin to breathe, it’s poisonous, there is no liquid water, there is no organized magnetic field to protect humans from harmful UV rays from the sun like we have on Earth, there would be constant exposure to radiation. They would need a constant supply of breathable air, soil and water.
We could not restock it like we restock the ISS. Whatever they have on Mars will have to come from Mars.
For these reasons and others I say no one is going to colonize Mars at all.
Just like the bottom of the ocean. Why don’t we go colonize there? It’s closer, just as dangerous, and more room than on Mars. We don’t because we’re stuck on this idea that we’re going to make our mark in space. We are going to survive as a species because our species is going to colonize other planets.