The amazing discoveries that New Horizons made at Pluto are showing us a new kind of planet. Yes, many of you might argue that Pluto is not a classic planet. On the other hand, settlers that one day will come to Pluto will not be so interested in origin and terminology, but in ways to terraform it. Also, many cold planets (or dwarf planets) exist for sure around more distant stars.
The Planet Edit
Surface Composition & Geology Edit
On a cold, frigid world like Pluto, what we might consider solid rocks, are in fact water ice and gasses. The mountains of Pluto are in fact made of water ice. There are many other substances, not as solid: The Heart of Pluto (Sputnik Planum) is, according to NASA, as soft as toothpaste and is made of gasses. If Pluto were large enough to sustain an atmosphere as dense of that of Earth, then we probably would have seen some strange liquids.
If we talk about Geology, things are far more different then what we see on Earth. On Pluto, settlers will have to adapt. Metals (like iron or copper) are probably as rare as gold and silver on Earth. The most abundant materials are water ice, tholins (organic materials) and many other ices.
As far as we know from Pluto and similar Kuiper Belt objects, some of them appear to be made of water ice, while others show to have large amounts of frozen methane (or other gasses) and tholins. It is also possible that a planet might have a crust made of over 100 km thick of frozen nitrogen and methane.
First of all, temperatures are very low. The planet will require huge amounts of greenhouse gasses.
Such a planet is facing some strange weather patterns. Even if it is orbiting the dim M - type stars, it will require a lot of time to finish its rotation around the star. This means very long years.
The third problem is about interstellar environment. Solar winds should be very weak that far from the parent star, so they will not create problems. If they are too weak, the interstellar wind would allow cosmic rays to reach the planet. These planets can have an internal dynamo, creating their own magnetic field. However, without an internal molten metal core, the dynamo effect will be weaker.
What would happen if you take Pluto to the orbit of Earth? It will become a giant comet. First, all gasses from Sputnik Planum will evaporate, then the water will be lost into space and then, after millennia, you will only find its internal, rocky core, probably smaller then Ceres.
A possible solution Edit
If the planet is larger then Pluto (for example something as big as Mars) and can support a large atmosphere, terraforming will be somehow possible. First of all, by warming the planet, its gasses will evaporate and will create a giant atmosphere. Then, as temperature rises, water ice will also melt. The problem is that we will create a planet with a giant atmosphere and with an endless ocean, with no solid ground. With the effects of greenhouse gasses, this will be possible, but since the amount of radiation received by the planet is small, it will take centuries to accumulate all the heat. Additional heat can be generated by atomic fusion.
Once temperature was acquired, the second step will be to do something with the atmosphere. One solution would be to transform existing gasses (carbon dioxide or monoxide, methane, ethane, nitrogen and others) into organic compounds that can float. This way, we can create a floating continent. The process can be done by using genetically-modified plants or bacteria (see Plants on new worlds for details) or to create a huge chemical factory. The first option will take a lot of time, while the second will require huge amounts of energy. Once finished, the artificial floating ground will still have major problems. It will not be as solid as a real continent and it can burn.
The third step requires for life to be inserted. Majority of plants that exist here on Earth, will find very difficult to survive with the weak luminosity found at Pluto or Sedna. Only genetically-modified plants will survive. And this will be a major problem for settlers.
Once terraforming was finished Edit
There will be major problems for settlers. First of all, since the ground can burn, any fire can end-up in a planetary disaster. Second, the planet will face a dangerous balance between received and lost energy. If the planet is as big as Earth, it will receive 1000 to 10000 times less energy from its sun then Earth does. Greenhouse gasses will keep the energy blocked and the planet will lose from radiation 1000 to 10000 times less energy then Earth. In these conditions, heat resulting from industrial activities can overheat the planet and destroy its equilibrium. Industrial development will be affected. Also, since the amount of sunlight received by planets is far smaller, there will be problems. If you want grain crops, you will need to provide them with extra light, or they will die. Extra light will create heat. The total population that can be fed is far smaller then if the planet were at Earth orbit.
Is it worth terraforming? Edit
Before starting to work, settlers will first ask themselves the most important question: Is it worth terraforming? What are the costs? What are the benefits? The process will take hundreds of years if not millennia and the costs will be far higher then on other planets. A civilization that developed interstellar travel, will prefer to look for a better planet in another solar system.
The best solution is probably paraterraforming. A planet like Pluto provides materials for many other terraforming projects. For example, it can be a source for water and gasses for an Inner Planet like Mercury. It can be a source for organic materials for industry. Once we move out from Earth, we will need another source of organic materials for rubber or plastic. Using tholins from Pluto might be a solution. Industrial colonization will benefit from this.
Paraterraforming can also be a hard job. Suppose we create a dome on the surface of Pluto. It will need to be well protected against the low temperatures outside. The weak light that comes from the sun is too dim to support life for many plants. Or, if some plants will survive, they will not be able to feed the colony. So, artificial light will be required. Another problem is that the dome must be protected from below. The surface below the dome might contain ices that can melt at -170 degrees Celsius.
An underground colony will also face major problems, because all walls will need to be well insulated. Heat from the colony can melt the walls. Also, tenuous amounts of gasses from the ground can infiltrate into the walls and enter the colony. We know that Pluto has carbon monoxide, a highly dangerous gas.
Major advantages are that all ingredients needed for life can be found there. There is always water. Carbon dioxide can be used for plants, while nitrogen can be directly supplied from the planet.
Colony on Pluto Edit
Now, let's imagine a space colony on Pluto. The model can be applied on many other planets.
The economy on Pluto should be focused on industry. Pluto has a huge diversity of terrains, from the nitrogen ocean called Sputnik Planum to the dark, tholin-rich plateaus of Ctulhu Regio. It also has mountains made of water ice and a lot of other types of terrains. The best place for a base should be between Sputnik and Cthulhu, between the youngest and the oldest (the lightest and the darkest) terrains. There, on a plateau, a city should rise, with a population of 4000 people. The city should be partially underground, because heat has a lower escape rate below ground. Majority of buildings should be well insulated and linked with surface or underground passages. A few domes can exist, with transparent walls.
Very important will be a power plant, that will provide heat and electricity to the entire area. The only available source of energy should be nuclear, with uranium brought from imports or a fusion power plant with existing hydrogen or deuterium. The power plant must have at least two separate generators. If one generator is closed, the other one must operate at once, or the city will freeze.
The economy must be centered on industry. There will be a quarry in each place where a desired organic compound is found. Also, a refinery will extract each raw material. A network of roads will be required, as well as a set of vehicles for them. But, what material can we use for roads on Pluto? The best and most abundant is water ice. It could even be possible to make a railway with rails of ice.
The huge refinery will be a source of pollution, just like here on Earth. The extraction process will leave behind deposits of debris. However, since Pluto has no life on it and humans cannot live there without protection suits, there will not be as many problems as on Earth.
Tourism can be another source of income. Visiting the huge variety of terrains found here, at the edge of Solar System, should be an incredible experience. The low gravity of Pluto is another thing that makes a trip more interesting. But, because Pluto is so far, visitors will be rare. It is just like today. If you live in Asia, a trip to Hawaii is too far and too expensive, so most probably you would prefer to go in holidays to somewhere closer to home.
In the end Edit
Terraforming of planets like Pluto is unlikely and highly expensive, but not impossible. At least in the nearest 1000 years. But, if we think further away, it can become a reality. A more advanced civilization that had overpopulated all planets in its solar system would like to terraform even a colder one. In other scenarios, an advanced civilization can transform a giant planet of a brown dwarf into an Artificial sun, creating opportunities for a Pluto class planet to be terraformed.