The "International Space Station" is "international" pretty much in name only. The United States funded (and continues to fund) something like more than 80% of its construction and operations and supplies roughly half its staffing. We'd supply more of the staffing but you have to have crew slots made available for the Russians and our other international "partners".
We've had "nations" for thousands of years and you expect us to "move beyond" them in a few hundred at most? What international cooperation we have today like Antarctica and the stuff in the space program are largely Cold War relics and not symbolic of anything greater.
I have a science background and I disagree with the claim that reproduction will be difficult on Mars. Yes, it will be difficult in low gravity, but we can easily design constructs that utilize rotational simulated gravity. And it doesn't have to be off-world like in a science fiction movie; a large clearing would accommodate such a construct.
Why? Corporations will never do it. Unless you're one of those who thinks Elon Musk and others like him are remotely serious in this.
Here's an article on space radiation that's relevant to this discussion. http://www.apollohoax.net/forum/index.php?topic=1147.0 I hope it helps.
Does anyone remember a LIFE magazine cover story from the mid 1990s that gave a six step process to terraforming Mars beginning with manned exploration in the 2015-2030 time frame and concluding with "complete terraformation" in about the 2150-2180 decades? It gave the changes to be made in Mars each step of the way, the technology necessary and even the cost estimates each stage along the way.
Terraforming Mars is hypothetical at best. We would need liquid water, we would need to greatly increase temperature, and we would need an atmosphere capable of blocking radiation. We can't have liquid water unless we raise the temperature. There is not enough indigenous CO2 to create an atmosphere. We don't even know if humans can make the physiological transition to Mars over the long haul? And if we pretend terraforming is possible, we're still left with a rock that has been constantly bombarded by radiation...except for some lowly microbes deep in Martian soil is the place sterile? IMO humans better find a way to get control of Earth to sustain and repair the ONLY place known in the Universe to allow humans to exist...
Radiation is not much of an issue once you have an atmosphere. You can obtain both water (which means oxygen as well) by diverting small asteroids and burning them up in the atmosphere. With nuclear power this is more than doable. And terraforming Mars would produce a wealth of knowledge regarding how to maintain Earth's biosphere which would prove invaluable to us in the future.
We need our magnetosphere to protect us from radiation. Our atmosphere doesn't do the job. If our magnetosphere went away, we would be in trouble even with our atmosphere from interstellar radiation as well as solar radiation.
Our atmosphere does part of the job. The ozone layer. Ever heard of it? And you can generate ozone. interstellar radiation is a minor problem at its absolute worst.
Earth, or I should say humans, will be long gone before we acquire your 'wealth of knowledge' from terraforming Mars...
There is an astronomical difference between what we are capable of doing and what we actually do. My prediction is in 200 years others will be on PF discussing the same issues we are discussing today...
True to the first but to the second don't simply assume you can project the inertia in the space program of the last few decades into the future in a straight line.
The light flashes astronauts see with their eyes closed are believed to come from cosmic radiation, particles with significantly more energy that solar radiation. These particles have the energy do disrupt dna. On Earth, we're protected from them by our magnetosphere. I'm not suggesting this is an insurmountable problem, as there are ideas on how sufficient protection could be obtained by forming at least partial magnetospheres. For example, humans who must stay in space for a while could have magnetospheres around their craft. And, similar ideas target bases in places where there is no magnetosphere.
Well, considering we do the cheap stuff first, stuff that doesn't involve solving the harder problems, I'm sure the cost won't be a straight line! So, I think we'll have to wait for some of these adventures until there is more justification for doing it. Of course, I'm more interested in science than than I am in "Buck Rogers" - which at least it targets the year 2419!!