Colonizing other planets in our solar system, or even orbiting other stars, is a perennial element of science fiction. It’s fertile ground for stories of every kind. But, practically speaking, will it be worth the tremendous effort required anytime soon? We could do it out of curiosity, or even the sheer joy of adventuring. In my personal opinion, the most pressing reason to spread Earth life to other planets is the “don’t put all your eggs in one basket” philosophy. Earth, or any single planet, is vulnerable to any number of doomsday scenarios, and we owe it not only to each other but to all of this planet’s life forms to preserve them here and ultimately protect them by transplanting them “out there” too.

What doesn’t pass the logic test is the assertion that we should colonize other planets because we need the room—that we’ve overcrowded our home and need to find new hospitable real estate. Yes, the most people-friendly land areas of Earth are overcrowded, but that’s actually a rather small percentage of the planet. Of Earth’s land mass, about a third of it is desert (defined as receiving less rainfall than it loses by evaporation) and a quarter is mountainous. So a little over 40% is more easily habitable, but that doesn’t mean it’s all inhabited. Huge tracts of boreal forest making up much of Canada and Russia are only lightly inhabited, partly because it requires a little more effort to eke out a living there, but mainly because people tend to crowd together along coastlines and large river basins. If we occupied all of the so-called habitable land space with the population density of the average city, we could house many times the current human population of seven billion. Of course, that’s not practical because, for now at least, we still need a lot of that land to produce food.

Contrast that with the habitation needs elsewhere in the solar system, where all food, water, and even air will have to be produced or imported. Even if we used up all of Earth’s easily-habitable land surface, there are lots of other places we could live on this planet with much less difficulty than creating extraterrestrial habitats.

The oceans: The most obvious (though not necessarily easiest) alternative living space on Earth because they’re a lot larger than the land—71% of the planet compared to the dry 29%—and they offer a lot of vertical territory as well as horizontal. In a brilliantly forward-thinking book I’ve mentioned before called The Millennial Project—Colonizing the Galaxy in Eight Easy Steps author Marshall T. Savage proposed colonizing the oceans first for practice and practicality. He envisioned floating colonies grown much like a coral reef, producing energy and fertilizing vast algae beds by drawing deep ocean water to the surface. The algae and other mariculture products would be a plentiful food source not only for each colony’s own inhabitants but exported around the world. There are other ideas for living on the ocean, but Savage’s is a good example. The ‘vertical real estate’ I mentioned—quantities of water to great depths—would be primarily for food production. Underwater habitation might be possible, but it would present many of the same challenges as a space colony.

Deserts: Possibly the easiest target for our expansion plans because the only real barrier to their habitation is the lack of water, and irrigating them would nearly double our habitable land space. If we can come up with a technology to produce ready supplies of water from the air, deep underground, or from the nearest ocean via desalinization plants and pipelines, we can render desert areas habitable even if they’re not necessarily fertile because of poor soil.

Antarctica: The south polar continent is included among Earth’s desert spaces, but offers even greater challenges because of its cold weather. Still, it’s not as cold or dry as the Moon or Mars (Mars can see temperatures in the area of 20C but also down to the -150C’s!) and other places we’re considering colonizing in the Solar System are even harsher. Heating is a factor of energy, and as we become more proficient at tapping the inner heat of the Earth, or maybe develop practical fusion energy, the Antarctic cold will be less of an issue. Not to mention that global warming may yet take hold there!

So far, I’ve looked at other geographical places where we might live, but in my next post we’ll get more creative and investigate some really interesting new digs, and the real meaning of “living the high life”.