I’m about as much of a fanboy and aspiring geek when it comes to outer space news and science as the next person, so I’ve really enjoyed following all of the recent stories about Mars. Whether you’re talking about the rovers we’ve landed there, the Martian orbiting satellites or the movies about putting human beings there… count me in. I have, however, made fun of the Mars One project on a regular basis and also turned a skeptical gaze on the private industry efforts of Elon Musk and others which are aimed at starting a colony on the red planet in the near future. I seem to have found a kindred spirit in the Washington Post’s science and politics writer Joel Achenbach, who comes to us this week with an opinion about how Mars is not a Plan B for humanity.

No one’s trying to dash anyone’s dreams here, but colonizing Mars isn’t simply a matter of rocket science. Musk and his colleagues have gotten good at rocket science (notwithstanding a couple of major failures in the past 15 months), but the biological part of a Mars mission is what’s so tricky: keeping people alive. We’re Earthlings. We are not adapted to Mars, much less interplanetary space. Technology can potentially solve a lot of problems, but we don’t even know what all the problems are.

Humans on Mars would be really cool. You could do a lot of great science. It would be a great adventure. The very process of trying to do it would surely have beneficial technological spin-offs. Musk and his fellow engineers are likely to make breakthroughs that will improve life here on Earth.

But Mars is not, for me, a satisfying Option B in case Earth becomes uninhabitable.

I have to agree with Achenbach and for many of the same reasons. But one thing which is left unsaid in his article is the simple reality that Mars is not a “natural environment” for humans. This can’t be overstated because it’s a common factor in all discussions of humans living in “extreme” environments, be it under the seas, in an orbiting space station or the clouds of Venus. (Yes, that’s been proposed.) You see, our advancements in science have allowed us to survive in all those environments – at least temporarily – but they remain inhospitable and, frankly, fatal in the event that the technology keeping us alive fails. And it will always fail eventually. You can build yourself a hut nearly anywhere on the surface of the Earth and if your hut fails you can still stagger outside and survive at least for a time. There’s air to breath. There’s pressure sufficient to keep your eyes from exploding out of your skull. And while you may overheat or freeze to death in fairly short order in some places, your body can at least maintain basic survival conditions for a time. (Hopefully long enough for rescue to arrive.)

That’s simply not true on Mars or anywhere else in the solar system. Once the technology gives out, the surrounding environment will immediately set to work killing you. The complete failure of a habitat (or suit) on Mars with nowhere else to go would give you a life expectancy measured in seconds. And despite science fiction discussions of terraforming the planet, that’s not going to change. To do so would take millennia if it’s even possible at all.

That’s not to say that we don’t need a Plan B. The biosphere of Earth is going to collapse and become unsustainable for human life as we know it. It’s simply a question of when. Short range disaster scenarios include a massive comet strike. At the longest, the swelling of the sun as it runs out of fuel will make the planet too hot for much liquid water in less than a billion years and our star will eventually consume the Earth entirely in four or five billion. In between those extremes are the horrible conditions which will come from the continents slamming back together in roughly 100 million years or the much more rapid arrival of either a global hothouse or the next ice age, depending which camp of scientists you listen to. (Both of those are probably survivable for us as a species, but it won’t be pleasant and a lot of people won’t make it.)

So what do we do? If we want a Plan B we’re going to have to get out of this solar system. We’ll need to find other planets with something very closely approximating our own atmospheric conditions and discover a way to get there. We may still require some genetic modifications to deal with whatever diseases and biological threats we’ll encounter, but the environment needs to be at least close to begin with.

I think we can do it. But it’s going to take a long time, a lot of money and serious dedicated effort by all of the industrialized nations on Earth. Plan B is out there, but it’s certainly not Mars.