On Tuesday, at an international aerospace conference in Mexico, Musk laid out his vision for how his SpaceX company will transport people to Mars in giant spaceships launched by giant rockets. On the launchpad, the booster and spaceship would be 400 feet tall, which is taller than the Saturn V moon rockets. This is why SpaceX refers to this colonial transportation rocket as the BFR, for Big [Effing] Rocket. Each spaceship will carry 100 people, or perhaps 200, Musk said. In a matter of decades, there will be 10,000 such rockets blasting off Earth every two years as Earth and Mars align in their orbits, he said.

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Give Musk credit: He thinks big. Musk, and people like him, will shape the texture of our lives in coming decades as we become an increasingly engineered civilization. With his company Tesla, Musk has disrupted the automobile industry by building popular and highly praised (albeit expensive) electric cars. With his company Solar City he is bringing solar panels to the masses. And with SpaceX, he plans to colonize the solar system, starting with Mars.

The reader should understand, however, that just as battle plans rarely survive contact with the enemy, forecasts of technological developments rarely survive contact with the future.

Putting humans — even a few of them — on Mars would be difficult to say the least. There's a long list of technical challenges, including creating robust life support systems that won't break along the way to Mars or once you get there. Radiation exposure from cosmic rays in interplanetary space is a significant hazard (though Musk dismissed it, rather blithely I thought, in his talk in Mexico). Long-duration flights in zero-g take a toll on the human body — and potentially on the human psyche. NASA will tell you that picking the right crew, with the right level of interpersonal skills and mental resilience, is critical to a Mars mission.

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And the thin atmosphere of Mars complicates efforts to land a spacecraft. It's diabolically thin: There's just enough atmosphere to cause friction but not enough to help much with braking. The U.S. is the only country to land a fully operational spacecraft on Mars. The largest U.S. payload was the Curiosity rover, which weighed roughly a ton. Any human mission to Mars would need a payload on the order of 20 times larger. SpaceX has been working on supersonic retro-propulsion, and that holds promise for landing large payloads on Mars. The "Red Dragon" mission Musk envisions in the next few years, with an unoccupied capsule, could demonstrate that technology, and you'd want to see it work a few times before putting human beings on board.

Musk’s plan assumes that there is a market for Mars transportation. The government doesn't have the budget for Mars colonization. Thus, the private sector would have to see Mars as an attractive business environment. Musk is willing to pour his wealth into the project, but this can't work as a charitable endeavor. So SpaceX would sell tickets to Mars. At first glance it's hard to see how this pencils out except under the most optimistic of assumptions about bringing down launch costs. And are there really huge numbers of people who would pay $200,000 (Musk's target price for a seat on his spaceships) to go to Mars? It's not the most hospitable environment. Among other amenities lacking on Mars is air. It's really cold. If you crave adventure, maybe start with a trip to Antarctica.

I asked Gentry Lee, a science fiction author and the Chief Engineer for Solar System Exploration at NASA's Jet Propulsion Laboratory, what he thought about Musk's plan for colonizing Mars. Lee was a key figure in the Viking mission of 40 years ago and knows a lot about the challenges of sending something to Mars. He replied by email:

"I think Elon's vision is exciting. But I think it is also important that people have some understanding of what it would take to implement such a vision. It would be a gigantic human engineering endeavor, greater in scope, scale, and cost than the Manhattan Project. To be successful the endeavor would have to develop and infuse new technologies at a much faster rate than we have ever achieved before on any project."

Bottom line: Technologically it's challenging but not impossible. You can get there from here. But don't pack your bags just yet.