The Triplanetary System

Colonisation of the Solar System

The colonisation of our Solar System will probably occur in the following sequence:

1. The Moon, simply because it's closest.
2. Mars, the best planet (other than Earth) for human colonisation for many reasons.
3. Mercury, which is reasonably close and not quite as challenging as Venus.
4. Ceres and the Asteroid Belt.
5. The moons of Jupiter, especially Callisto, Ganymede and Europa.  While much further away (5 AU), they are still easier to build bases on than Venus.  Io's surface is slightly too dangerous.
6. Venus.
7. The moons of Saturn, especially Titan.
8. The moons of Uranus, especially Ariel and Umbriel.
9. The moons of Neptune, especially Triton.
10. The Kuiper Belt and beyond.

(I have this crazy idea that the sequence for planetary colonisation is encoded in the days of the week: Monday = Moon Day, Tuesday = Tiw's Day (Tiw = Mars), Wednesday = Woden's Day (Woden = Mercury), Thursday = Thor's Day (Thor = Jupiter), Friday = Freya's Day (Freya = Venus), and Saturday = Saturn's Day.  The Moon, Mars, Mercury, Jupiter, Venus, Saturn - a logical colonisation sequence.  Is it possible that God somehow planned it that way, to plant the seeds of interplanetary colonisation in our subconscious?)

Of all the worlds colonised by humans, the Moon and Mars will be by far the most important.

Luna, the Moon

Luna is interesting and valuable for a wide range of reasons:

• Close to Earth and the Sun.
• Lots of valuable metals such as titanium.
• Best place in the Solar System to find helium-3.
• One of the best places in the Solar System to learn about its early history.
• Great place for holidays, sports and recreation!

Mars

Mars also has many qualities which make it especially important:

• Reasonably close to Earth and the Sun.
• A diurnal (day-night) cycle almost the same as Earth's (24h40m)
• An axial tilt and seasons like Earth.
• Temperatures not too extreme.
• Water, atmosphere, and lots of useful metals - everything needed for life and for colonisation.
• Spectacular geology and geography to explore.
• Can be terraformed, i.e. potentially able to host an uncontained planetary biosphere.

The Triplanetary System

That's why these two planets receive all the attention when talking about space colonisation.  Over the next century, our Solar System will change, because people will be living on 3 worlds instead of just one.  There may be bases built on other worlds such as Mercury and Ceres and Ganymede, but the populations there will never grow at the same rate as those on Luna and Mars because the locations simply aren't as good.

The economic drivers that lead to construction of bases, towns and cities on Luna and Mars will also propel the development of space technology, especially in areas like space communications and transportation.  The distances between these planets will grow smaller, just as the distances between continents on Earth has narrowed over the centuries.

Trade routes will be established between these 3 planets, carrying metals, coal, food supplies, seeds, gases, construction materials, electronics and other products between them.  An Earth-Luna-Mars internet will be built (and is already being built) to provide communications.  While many people may live only on one world, many will travel between them regularly, for business and pleasure.

The Solar System in 200 years will be like Earth today, with its 3 large continental land masses (Earth will be analogous to Eurasia-Africa, Mars to the Americas, and Luna to Australia).  Each planet will have its own cultures and identity, but there will be a lot of communications, commerce, sports, tourism, friendships and agreements that bind them to each other.

The Moon or Mars?

There has been considerable debate in recent years about whether it is more important to focus our space colonisation efforts on Luna or Mars.  In my opinion, this is like discovering the New World and arguing about whether to colonise North or South America - as if you have to pick one.

There are many more people interested in Mars than the Moon, which is understandable because Mars offers more.  But the Moon is still awesome, and it's much easier to get to.  It does not have to be a contest, because (a) it is absurd to think that only one of them will or should be colonised; (b) the people who want to go to the Moon will go there anyway, and the people who want to go to Mars will go there anyway, and (c) they can be colonised together in a harmonious program.

The colonisation of Mars is particularly challenging, mostly because of the distance, and because many of the technologies needed are untested.  This really highlights the blessing that is Luna.  Luna is always only 3 days away at the most, so if anything goes wrong during our early attempts at colonisation, people can be brought back to Earth very easily.  Early pioneers will be high quality humans so health and safety must be a priority.  From Mars, the shortest trip (using current space transportation technology) is 6 months at best.

Besides, many of the same challenges exists on Luna as they do on Mars - temperature extremes, high levels of radiation, ubiquitous dust, low gravity, and the absence of a breathable atmosphere.  By conquering these challenges on the Moon, we will be well-prepared to colonise Mars.