So you—or the space agency that you work for—have decided that humans are too good to be confined to the Earth. With that spark of manifest destiny helping to illuminate your path, there is no stopping you from pulling up stakes and heading out to any of the nearby worlds that are so seemingly destitute of life as we know it that they are practically begging to be colonized.
Step One: The Moon
I may be paraphrasing here, but someone once said, “A journey of a few million miles starts with a stop by the grocery store.” The grocery store for this trip is just down the block, only about 250,000 miles away. Though you won’t find any cases of Mr. Pibb on the Moon, what you will find is water: Buckets and buckets of water, according to NASA. One of their recent missions discovered that that place is just lousy with crater-shaped ice cubes of water. Water is also thinly dispersed over its surface.
The Moon is much smaller than the Earth, on the order of 1/80th the Earth’s mass. So, once you are out of the “gravity well” of the Earth, it can eat your interplanetary dust. The escape from gravity makes the Moon a great staging area to “daisy-chain” your travels to other worlds, but just like the grocery store, it’s got its own thing going on too.
NASA has been seriously considering using “inflatable habitats” for doing work on the Moon. These habitats are akin to camping on the Moon—you make your way there, set up the tents and get to work on building your winter cabin.
The crust of the Moon—called the regolith—is a great place to take refuge. Refuge from astronaut-killing cosmic radiation. Going outside the protective magnetic field of the Earth is a dangerous prospect. Cosmic radiation is not like getting the arm that you’re hanging out the window of your car a little sunburned. Oh, no.
The Sun, in addition to putting out a lot of light, streams out radiation all of the time in the form of very, very energetic particles. These energetic particles are brimming over with energy, have the ability to penetrate everything but the thickest of materials, and basically can give you wicked cancer, in a hurry.
So, building a little hidey-hole in the Moon to escape these solar death-rays is an absolute necessity. This is pretty much the case on every other body with a “surface” you would be able to visit in the Solar System.
Shielding yourself from cosmic rays is a huge challenge for designers of spacecraft. Most designs currently being dreamed up—not many have been thoroughly tested—involve putting all of the food and water that astronauts would need on an interplanetary voyage into the walls of the craft. In essence, you surround yourself with your supplies. As you eat your freeze-dried ice cream and suck down your Tang with gusto, well, what comes around goes around. Being surrounded in a capsule that sandwiches you with your own bodily waste sure beats dying.
Once you make your stop at the Moon to get your water and split it up into suitable hydrogen for fuel and oxygen for breathing, you’re basically free to follow your fancy.
Step Two: Mars
If you have a hankering for a “rustic” place to visit, Mars is where you should steer your spaceship with fuzzy dice hanging in the window first. It’s the dream of every space agency worth its rockets right now to send a human to Mars.
The surface of Mars isn’t exactly welcoming—huge dust storms can blind you for days on end, and the average temperature is -63 degrees C (-81 degrees F). Nighttime temperatures on the Red Planet can dip down to -110 degrees C (-170 degrees F).
Mars is red because the outer layer of its regolith is basically composed of fine rust. That’s right, rust. If you’ve ever spent time in a desert, you’ll know that sand gets into everything and is hard to get out. Mars dust would be worse; a fine red, gritty powder that’s gonna make your airlock look like a bomb of jeweler’s rouge exploded in it. It has been hard on most of the rovers and landers we’ve sent there, and it will be even harder to wash out of a white spacesuit. It’s a manageable problem, though.
There’s probably more water on Mars in the form of polar ice caps than there is on the Moon, and it boasts a predictable array of seasons. Its tilt is roughly 25 degrees, close enough to Earth’s 23.5 degrees to give it seasons similar to ours. It has a year that is 684 Earth-days long. Its seasons are, however, about twice as long as those here, because it takes Mars roughly twice as long as the Earth to orbit the Sun. For example, the summer on Mars lasts 194 sols—Martian days, which are 37 minutes and 22 seconds longer than ours—as compared to the 93-day summer that we have here on Earth.
A colony on Mars would be cool, but given that it has 1% of the atmosphere that we have on Earth, the chances of going for a walk in the warm breeze are rather remote unless you take up some serious terraforming. Like, hundreds of years of intensive terraforming. This atmosphere—made up of about 95% carbon-dioxide—could be transformed with a bit of creativity and solar energy to breathable air. It’s a lot of work, though, for something that won’t be ready until your great-grandchildren are grown.
Making small “biosphere”-like enclosures for the colony is more likely. That pesky cosmic radiation is again going to be a problem on Mars. The magnetic field created by a dynamo of a spinning core inside our warm, gooey lava-filled Earth keeps that radiation from making us all end up with horrible cancer. Mars lacks a core like ours, and so its inhabitants will be exposed. But if a colony is sufficiently shielded inside the wall of a crater, a Mars habitat might be downright cozy.
Step Three: The Asteroids
If you’re into get-rich quick schemes and can find a mining company with the capital to invest in a rocket fitted with mining tools, making your way to an asteroid or comet is definitely the next step towards manifesting your destiny.
Larger asteroids of the metallic variety would be chock full of precious metals. A single asteroid with the diameter of 1 km could contain metals worth upwards of twenty trillion dollars. Just like with gold or oil or platinum here on Earth, all you have to do is go and get it! Which is harder than it sounds, given that you have to find such an asteroid, and then plot its orbit, and then find a way to rendezvous with it. Keep in mind that while you’re living on the asteroid and running a huge drill, you are transferring all of that mass to yourself, and then have to get back to Earth. One way to manage it is to find an asteroid that contains a sufficient amount of water or carbon-dioxide ice, which could be used as fuel to bring the mined materials back to Earth.
A better strategy might be to drive a spacecraft out to the asteroid and gather any ices it contains for fuel. Then, strap on some rockets and haul it into a nearer-Earth orbit (like somewhere outside the orbit of the Moon, as you don’t want to unsettle the natives) and mine it from there. “Colonizing” an asteroid, while potentially profitable, shouldn’t be one of your long-term goals.
Step Four: The Icies
Past the asteroid belt, other places in our Solar System potentially suitable for humans to set up shop are Enceladus and Europa. You wouldn’t want to hang out on the surface of them for very long, as they are both coated in a thick crust of ice and lack much in the way of atmosphere or energy. But the planets they hang around—Saturn and Jupiter—both are monstrosities that tug on the innards of their tiny moons, which in turn continually churn up the guts of these small celestial bodies to make them big balls of water with a rocky core.
Living underneath the ice of Europa or Enceladus—the latter of which has actual geysers that shoot into space, putting Old Faithful to shame—would give you plenty of protection from cosmic rays, and give you a chance to drive around in a submarine (think Abyss, but darker and hopefully without pathological members of the military trying to nuke everything).
Since both of these icy moons lie so far away from the Sun, setting up solar cells on the surface wouldn’t do you too much good. However, you could use the thermal energy from the water outside of your little sub-bubble to power lights, grow food (I hope you like algae), and generally keep the harsh environment of space at bay.
Once you get past this point in the Solar System, there’s not much out in the boondocks that you’d want to spend any length of time visiting. Neptune and Uranus are just too gassy to land on, and their Moons receive so little sunlight that powering and heating equipment—not to mention growing food—become daunting tasks.
So remember: Find plenty of water, get plenty of sunshine, line the walls of your spacecraft with your own excrement, and you are well on your way to colonizing the Solar System!
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