Blow stuff up!

radiation because its thin atmosphere than the radiation that would fall to the surface.

Radioactivity and radiation are different.
Radiation on Mars surface is similar to the ISS.
There is very little radioactivity on both.

look how rapidly it was rising before the Partial Test Ban Treaty in 1963:

https://en.wikipedia.org/wiki/Radioactive_contamination

And a 2 for 1 deal with extra CO2 and water if comets were used instead.

Of course, the morality of doing this is another question.

All of our eggs are in one basket.

Wouldn't it be cheaper and faster to protect the one we have?

...IF we can move our highly $$$-polluted political system to do it.* It hasn't been responsive to the needs and desires of the majority of people on most issues, since, oh, say Reagan. We have a lot of work to do, as a citizenry.

However, even if we were to clean up the political system, starting in 2016*, and start seriously greening the country and the world, the truth is that the Earth can no longer handle our numbers. We are too many for Earth's resources, and human population growth shows no sign of slowing down. This is one reason why I STRONGLY support NASA and its associated projects. We are very likely going to need a second Earth. (Some NASA projects are also important for understanding and restoring or terraforming planetary environments, including Earth's.)

I believe that space exploration and colonization of other worlds is our destiny. That's my reading of human history, and of the story of Earth itself. All other species fit their numbers to available resources. Not us. Why?

Until now, we've had what seemed like endless fertile territory to expand into. And we've just grown and grown and grown, as a population. Now we're up against Earth's limits even if we start serious worldwide greening tomorrow. I think that there is something in our natures, as human beings, that is pushing us "out there" to the great Universe.

We do, of course, desperately need to learn the lessons of this crisis period, where our political, economic and military systems are doing us in, as well as obliterating other species (including what are likely sentient species such as dolphins) and gravely damaging, if not destroying, the very benign planetary environment that begat us.

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*(Our vote counting system is highly compromised, with every system in the country based on 'TRADE SECRET' programming code--code that the public is forbidden to review--with NO AUDIT AT ALL in half the states, and a miserably inadequate 1% audit in the other half. This system has, and will continue to be, rigged in favor of idiots and outright fascists, until we wake up and throw these corporate-controlled machines out of our system. Not much hope of reform in 2016. This 'TRADE SECRET' vote counting system was created to keep real reformers out of high office, and works in tandem with the filthy campaign contribution system and corporate 'news' monopolies. The death-throes of Planet Earth may get disruptive enough to move even idiots and fascists to do something about it, but their solutions will be the worst kind. Count on it.)

I seem to recall that Mars once had a more significant atmosphere than it does now, but it diminished a long time ago because of the planet's low gravity. It seems any attempt to terraform Mars would be doomed to fail for the same reason.

Perhaps communities built within domes would work better. They could be built with 3-D printing on a massive scale using local resources.

above the poles, concentrating the suns rays directly onto the polar ice caps to melt them. Probably safer than nukes I would think.

He said "there's a fast way and a slow way&quot to warm up Mars).

Beware the YouTube vid that ends after the fast way.

I'm curious also why we don't have small ships going to the moon now and sending back nice HD footage.

There are also other options.
The L5 Society wanted to colonize L5 first.
Others want to colonize low earth orbit first.

Most space enthusiasts want to see all of those eventually,
but get into heated arguments over which to do first.

Musk is a Mars-first person, but he's said he wants to be like a trucking company, if the Moon-first or whatever-first people can pay, he'll gladly send them on his rockets.

So I think things are going to get very interesting once he has a fleet of re-usable rockets!

Nuclear weapons for positive use? Uh, no.

As someone above mentioned, Musk told Colbert there's a fast way and a slow way.

Musk later tweeted that he wasn't suggesting we do that.

Until that is solved, dreaming of space exploration is a pipe dream. We currently pay the Russians $85,000,000 or so for a seat to the ISS.

Where is the money coming from to build anything?