Here is my 12 step plan:
Step 1: Find the Right Size, Perfect Distance
I cannot over stress the importance of this step. If we skip it, the project will fail. We need the perfect size planet. If the planet is too big, the planet's gravity will hold too much atmosphere, resulting in crushing pressure at the surface. However, if the planet is too small, the atmosphere's gaseous molecules bouncing off each other will eventually fly off into space, because their average speed exceeds the escape velocity of a small planet's gravity. Mars is the poster-child for that scenario. It had an atmosphere once, but it's gone now because Mars is too small. Now, Venus is about the size of our planet, but she is our go-to example of a planet too close to the sun. A run-away greenhouse effect makes the average surface temperature of Venus 864° Fahrenheit (462° Celsius). We won't get many colonists signing up for that!
You won't be getting very far without a dedicated team of engineers, scientists and support staff in a comfortable self-sustaining residence. When things go wrong - and they WILL go wrong - you need a crew capable of fixing things before they get out of hand. The distances are far too great for command control at home to do everything remotely.
The planet will be a barren rock at first. So, without an atmosphere, any water we add would just freeze. And we NEED water. So we must enshroud the planet with life sustaining air. Atmosphere formation will also focus on generating tons of water vapor to prepare for Step 4. In fact, the resident crew won't see their sun for a long, long time. Humidity will be at 100%, with a pea-soup-like fog everywhere.
The resident buildings will be air tight and strong enough to withstand high pressure, because they will now be underwater. In this step, the foggy atmosphere will release most of the water vapor and precipitate on the planet as liquid water. We will keep this up until the entire planet is covered with water since we will introduce life to the ocean first. We won't wait for the atmosphere to be "human-ready" before introducing life, however. The early stages of our own planet had the same scenario. Part of the plan is to allow time for the organisms to live and die. That will enrich the silt that accumulates on the sea floor. You see, we are thinking ahead to Step 8.
As the water settles out of the sky and into the ocean, our resident crew will finally start catching glimpses of their sun. Eventually, they will enjoy blue skies, fluffy clouds, sunrises, sunsets, thunderstorms, wind and the stars at night. They will have to come up to the surface to enjoy the beginnings of these atmospheric pleasures, though, because the ocean still covers the entire planet. We want that valuable sea silt to build up and don't want to leave even one section of land exposed to remain barren. We have important things to do with that organic matter. So let it coat every square foot of the planet.
Here's an analogy to help you understand why we start simple. Long ago, some humans had aquariums. If they put a fish in a fresh tank it would die. The tank was too barren and had to be seasoned by establishing a cycle where bacteria would convert the ammonia from fish waste into nitrite and then into nitrate. The latter being the least toxic to life. They could speed things along by adding water from an established tank that already had bacteria. As these chemicals came under control, they would add sturdy, inexpensive fish until it was stable enough to add their prized angelfish. We'll need to do the same thing in our new ocean. So, we'll start with bacteria, algae and hardy single-cell organisms like our planet's pre-Cambrian seas. The bonus now is that the algae will start converting CO2 into oxygen.
Now we'll introduce complex lifeforms a little at a time. Remember, our atmosphere is still not "human-ready" so make sure our lifeforms can stand the current make up of the air and sea. Most of these won't survive the transition to a "human-ready" atmosphere, so don't get too attached to them. In fact, why don't we have some fun and make some really crazy plants and animals. What we are emulating here is our planet's Paleozoic seas. We'll eventually introduce more complex life, in as many varieties and sizes as possible - including giant animals similar to our Mesozoic oceans. The more biomass there is to live and die, the richer the seafloor silt will become.
Next we'll expose some landmass. We'll bend the crust of the planet to form sea basins and continents. Even better! We'll make sure it is one landmass. A supercontinent. That way the dissemination of life will be easier (see Steps 9 and 10). We'll leave the majority of the planet as ocean, however, for a more naturally stable planet. The oceans are the lifeblood of the planet, driving the water cycle, the weather patterns and oxygen-carbon dioxide cycle. The built-up foundation of silt laid down in steps 6 and 7 will now provide some topsoil to support the land life we will introduce in the next step. We aren't just doing this so our colonists will enjoy a beautiful place to live, the ecosystems we are building are the key to a self-sustaining planet.
So now we have some topsoil to work with, but we can't get carried away and plant a rose bush, yet. The soil will barely support hardy plants and small animals. Let's be pragmatic and start with algae, moss and plants that reproduce with spores. We'll save those seed-bearing flowering plants until later. We will include worms, insects and other creepy-crawlies that thrive on scavenging dead stuff, like the Devonian and Carboniferous periods. As we gradually add more complex land life we want something to clean up the mess and add to enriching the top soil.
Now comes the fun part. We'll gradually fill the continent with complex lifeforms. Reptiles, birds, mammals and seed-bearing plants of all kinds. And again, we'll try to include as many giant animals as possible, to speed things along with a large biomass. In fact, if we didn't have to worry about our resident crew's safety, now would have been a great time to create some big, scary monstrous creatures. But, alas, we'll have to be content with more placid predators.
If we did everything right, now all we need to do is take time off and watch our new world establish equilibrium. As more time passes, the more stable the planet will become. The wildlife and their environments will evolve jointly into thriving ecosystems. This would be a good time for our residents - who have grown to be a rather large population by the way - to take a much deserved rest and to enjoy the beautiful world they helped create.
The moment we've all waited for - and it has been a long, long wait. Terraforming a planet doesn't happen overnight. But all that effort was worth it, because the rest of the humans are coming in their colony ships. We pioneers who first set this project in motion have long since passed away, but our offspring should honor our memory by taking good care of their new home. They have been watching things unfold and waiting eagerly for this time to arrive.
Why does this all sound familiar? Wait a minute, I remember! I read about a similar plan in an ancient book. The first and second chapters had two separate "creation" stories.
The first chapter was the blueprint or planning stage or spiritual creation - whatever you want to call it.
The second chapter had a very scant explanation of the physical creation, yet the order that was laid out was curious.
First, there "went up a mist from the earth, and watered the whole face of the ground." (Sounds like my foggy atmosphere.) Then man was created about the same time as plants and he was given a pleasant home. Why? It sounds like the workplace for an on-site manager to me. (Much like my resident oversight crew.) Then man was joined by animals of all kinds. When his job was done, "a deep sleep [fell] upon him" and he was given human companionship in the form of a mate. He was probably made to forget about his role in the creation, too.
Furthermore, the "lights in the heavens" were not "created" until the fourth day. Again that sounds like what I expected in my plan about the the sun, moon and stars not being visible because of the thick cloudy atmosphere. Even the mention of the "waters under the heaven [being] gathered together unto one place, and [letting] the dry land appear" perfectly mirrors my plan to start with a global ocean then creating a continent later.
I tried to pattern my plan after the history written in the rocks of our home planet, but it is interesting how closely it imitates the plan written in that ancient book. That book said the planning took 6 days, however it didn't say how long the physical creation took. I bet it took a long time. Our little exercise in terraforming suggests that it would have taken a long, long time. (Read also: Science and Religion: Both Dating Methods Are Wrong)