What is Terraforming?

"Terraforming is the process of deliberately modifying the atmosphere, temperature, surface topography and/or ecology of a planet or moon to make it more similar to that of Earth. Simply put, it's the process of taking a dead, inhospitable world like Mars, and turning it into a place where plants, animals, and humans can live and breathe freely on the surface. At the end of a terraforming project, humans would be able to live unaided on an alien world, as naturally as they would on the surface of Earth.Naturally, this is a tremendous task to undertake. Our own alterations of Earth, however potentially disastrous, have been mere nudges relative to the massive efforts that would be required to remake an entire planet in Earth's image. Without a doubt, it would be the single largest and most expensive undertaking in human history. But make no mistake: it is possible. And, some argue, unavoidable.PROCESSPlanets are big things, and altering one is a huge undertaking, but the processes involved are actually quite simple. Many of the techniques have their origins in 19th century science and basic chemistry. Each planet will present its own difficulties, but every terraforming effort can be reduced to the same five priorities: global temperature, atmospheric pressure, atmospheric composition, water, and the biosphere.Each of these priorities can be addressed in an infinite number of ways, and inevitably they will begin to clash: increasing the carbon dioxide in a planet's atmosphere will warm the planet up, but converting it into breathable oxygen will cool it back down, etc. Balancing these different objectives, advancing toward each goal simultaneously without overdoing any one priority at the expense of the others, will be the true challenge of terraforming, and forms the core gameplay mechanic of TerraGenesis.TIMEFRAMEIf you're beginning to think this sounds like it would take a very long time, you're not wrong. Even the most ambitious estimates for how long it would take to terraform a planet are upwards of a century, with others ranging from multiple centuries to millenia. Planets are large things, and it takes enormous effort to alter them significantly. Undeniably, terraforming is a long-term investment.That being said, such timescales do not make terraforming impossible, or even necessarily impractical. The pace of modern living makes a century seem like an eternity, but consider this: the great cathedral of Notre Dame in Paris took over 100 years to build, York Minster Cathedral took over 250, and completion time estimates for Petra in Jordan range from 450 to 850 years. The Great Wall of China was built in a series of pushes over the course of 2,000 years. Humanity is no stranger to long-term engineering projects. And of course, modern and as-yet-discovered technologies could speed up the process of terraforming considerably. CANDIDATESAny discussion of which planets are best-suited for terraforming has to begin with Mars. Though significantly smaller than Earth and with less protection from solar radiation due to its lack of a strong magnetosphere (the magnetic field that makes compasses work on Earth). Mars remains a better candidate for terraforming than we could have ever hoped for. With water on the surface, a pre-existing (if dangerously thin) atmosphere, as much dry land as exists on Earth, two usable moons, and an orbit next-in-line to our own, Mars seems hand-made for the purpose of terraforming. In fact, many astrophysicists and geologists have suggested that Mars may have been much more Earth-like in the past, even without our efforts.Beyond Mars, things get more difficult. Venus is the closest planet to Earth and almost exactly the same size (and thus has very similar gravity), but the surface is a nightmarish hellscape of air thicker than sea water and temperatures hot enough to melt lead. Mercury is the only other rocky planet in our solar system, but it is too close to the Sun for terraforming to be practical. Several moons have been proposed as options for hominization, though their smaller size and vast distances from the Sun would present major challenges as well.That being said, the rapid discovery in the last few years of hundreds of exoplanets, (planets orbiting stars other than our own), will almost certainly open up countless new options for exploration and terraforming, whenever the challenges of interstellar travel are finally overcome."