Pollution is the ultimate result of human civilization. Since we discovered fire in the stone age, we have been polluting the environment. But how far will this go?
Pollution terraformed worlds Edit
It is most of sure that human civilization will pollute the newly terraformed planets. Their new ecosystems will be more fragile then what we have now on Earth, so we must be very careful.
In the first 100 years, new ecosystems will be more fragile. Plants and animals will try to conquer the new world. The climate will change sometimes dramatically until it gets to an equilibrium state. Water will dissolve toxic minerals from the ground and the ground itself might contain toxic compounds. If we add human pollution to this, we might send the planet to a runaway sentence to death.
Air pollution Edit
Human activity creates many dangerous gasses. Probably the most dangerous of all is carbon dioxide, that has to be strictly limited. In case of an Outer Planet, there is a huge risk that this process will degenerate. Outer planets receive only limited light from their sun. So, you have a very small solar energy that reaches the planet and you have to limit the thermal radiation up to a value that will block enough heat on the planet. If you increase the greenhouse effect, temperatures might rise to deadly values. Also, there might be chemical compounds able to react with the greenhouse gasses and destroy them, sending the planet to an ice age.
On an outer planet, winds are very slow. Gasses in the air are not well mixed. Air stagnation will result in stratification of toxins. Methane and ammonia are naturally formed in low amounts in nature, but they are degraded. Without winds, these gasses will move to the upper atmospheric layers. Carbon dioxide is heavy and will condense on low altitudes. We must avoid processes that can result in massive accumulations of these gasses. This is one reason why Population Limit is set to so low values for outer planets.
On an Inner Planet, without atmospheric shields, the planet will naturally enter a runaway greenhouse effect. We must be very careful with any greenhouse gasses.
Water pollution Edit
As we well know, chemicals dumped in water are transported by rivers into the oceans, where they slowly accumulate into larger amounts until they become toxic. We must avoid at all costs doing what we have already done on Earth.
There also is another way of pollution that most of people don't realize today. River diversions for hydro energy and for irrigation are always affecting the rivers, sometimes much harder then chemicals. If you take 70% of water from a river, it will flow much slower and sometimes become unable to transport sediments. Its waters will get hotter and will have less oxygen, resulting in a decrease of fish population.
Soil pollution Edit
Industrial centers and residential towns will certainly affect the ground beneath them. But this is not the most dangerous of all. First of all, we tend to create large quantities of garbage, as much that on Earth we have already built hills of it. The second major concern is industrial waste. We must be very careful with these.
Global pollution Edit
There is a new category of pollution, that we don't see today on Earth. The main reason for this is that Earth is far more stable. It resides in the center of a habitable zone, it has the perfect ratio of minerals for life, it has enough gravity to hold a stable atmosphere and still we haven't pushed the ecosystems to the limits. Other planets don't have all these facilities.
Except for Venus, all other terraformable objects in Solar System are smaller. Less gravity means that their atmosphere will more easily be scattered away by solar winds. For Venus and Mercury, the risk of a runaway greenhouse effect will be high. For the moons of the gas giants, there are two major risks: to lose their atmospheres and to make a hole in the greenhouse layers. Luna and Mars are more stable.
Global pollution refers to a change in the environment that can disturb its equilibrium state to a point where its ecosystems will be radically affected and unable to repair without an external intervention.
During terraforming process, the former carbon dioxide is transformed into atomic carbon (black powder) and oxygen. The carbon must be kept away from contact with the atmosphere and sources of fire. If it somehow ignites, the planet is doomed.
Another major thread to a planet with a fragile ecosystem is a war. Earth survived many atomic blasts without problems. However, if you detonate an atomic bomb on a terraformed Triton, the blast will make a hole in the layer of greenhouse gasses and will have catastrophic effects on the entire moon. The same would happen in the case of a major explosion.
Pollution on asteroids and airless moons Edit
Without an atmosphere, everything will remain still on the surface. Asteroids and small moons will not be terraformed. Maybe they will be paraterraformed. Industrial colonization will affect many asteroids. Without any threatened ecosystem, industrial corporations might have no reason protect the nature. Toxic waste, garbage and abandoned constructions will remain immobile on the surface. For how long? Probably for billions of years. On an asteroid affected by heavy mining, full with deposits of toxic waste and covered with the ruins of former industrial corporations, settlers will avoid to go. That celestial body is marked forever as inhabitable.
Cosmic pollution Edit
Since the beginning of the cosmic era, space around the Earth has become overwhelmed with objects. Without the effects of an atmosphere and of life, these objects will probably be there for millennia. As the space age will continue, the number of objects will increase, not only around Earth, but also around other planets, moons and asteroids and even on heliocentric orbits.
Galactic pollution Edit
Now, let's take a look into the future. As human civilization extends beyond the Solar System, pollution will also extend to other celestial bodies.
At some point, humans will try to do things that are impossible today. The creation of an Artificial sun from a giant planet will affect the entire solar system. When we will be able to extract energy directly from stars, this might lead them to instability. As new transport ways are invented, they will also have other effects. When we will create vehicles able to fly faster then the speed of light or when we will create wormholes, we might disrupt the fabric of space, creating ways of pollution that we never imagined possible.