Geographic features on a planet or moon will affect air humidity, wind currents, hydrographic basins and overall climate. So, pioneers that will work on terraforming and settlers that will go to their new worlds will have to take care of geographical features. Please note that for terraforming it is not important how these features were created. The goal of our wiki is to see how celestial bodies can become new Earths.
Initial Geography Edit
Main article: Geographic Pattern - Craters
Main article: Geographic Pattern - Erosion
Main article: Geographic Pattern - Tectonic
Before terraforming, a celestial body will have certain geographic features. They will be heavily affected by terraforming processes, because of many processes. In the end, depending on ground conditions, the planet might look almost the same or might be unrecognizable. These features can be divided into 3 groups, based on the forces that model them:
- Impacts create craters. Depending on the celestial body, surface might be covered with almost 0% up to 100% of craters. In some places, like Callisto, Ceres or Mercury, we see craters created over other impact basins.
- Tectonic features include rifts, canyons, mountains, volcanoes and faults. These features are found on many planets and moons, geologically active or inactive.
- Fluid erosion is made by liquids and gasses, including two different types of land. One is found anywhere on Earth: erosion (valleys) and sedimentation (deltas), made by flowing liquids. The only celestial bodies with valleys are Mars and Titan. Winds can create dunes, as seen on Titan.
- Plains exist also in outer space. The best examples are the 'seas' on the Moon.
Before the terraforming process starts, scientists must carefully analyze the geographical pattern of the targeted planet. They will need to also conduct a complete geological research, to know how things will interact with each other.
The overall altitude variation is an important factor. In case of Venus, where most of the land seems to be at the same elevation, the amount of water needed to create an ocean will be smaller then Earth's oceans. Also, if a planet hosts high mountains, they can reach above the greenhouse gasses. In case of the huge volcanoes on Mars, they are so high that on them, conditions will remain similar to how the planet was before terraforming.
During terraforming process Edit
In some cases, like Europa, nothing from the initial crust will remain, the entire moon will become an ocean. A very advanced civilization will be able to remove part of the water until the rocky core of the moon is exposed.
In other cases, transformation will not be so severe. As the ice melts, it will create a massive flood. A Noah's flood, literally. On Mars we know that its water is frozen beneath surface. When the planet heats and ice melts, rivers will first come to life, as violent muddy torrents. This will shift their valleys. The force will be so huge, that it can be able to move mountains. The process will clear the long dried Martian riverbeds, that today are blocked by impact craters.
If water is trapped somehow in the atmosphere, it might be possible to create rain by cooling the planet. In case of Venus, we know that there is only a tenuous amount of water, however the sulfuric acid can be separated into water and sulfur oxide. To limit the effects on the ground, settlers might try to divert comets to Venus while it still has its initial atmosphere, so that water will be uniformly distributed and impact craters will not be formed. Then, if somehow we cool Venus and release all water to the ground, it will create something like Noah's flood. A massive rain, lasting for many days will create huge rivers that will erode the landscape, as the oceans will take shape.
In case water is brought by impacts with diverted comets, we will see a different scenario. Each impact will send shock waves into the forming atmosphere, with a global impact. There will be created a lot of impact craters, but also a lot of violent storms, tsunami waves and earthquakes. All these will model the planet more and more. This is the proposed terraforming model for Luna and Mercury.
One major challenge will be rivers. On Earth, rivers (with some exceptions) are close to an equilibrium phase between erosion and sedimentation. The key to this equilibrium is the slope. If declivity is increased, rivers will erode more. By the opposite, if declivity decreases, rivers will move too slow to carry their sediments. A lake on the middle of a river also is a challenge. Sediments will accumulate inside the lake, while downstream, water will erode its path, because there will be no sediments to counterbalance erosion force. If the planet has its own valleys, like Mars, there will not be major challenges. But if the planet has other features, water will start working. If a massive Noah's flood firstly occurs, it will create the primordial network of valleys for the new rivers.
Geographic engineering Edit
Scientists must work on many simulations, to see how the climate will look like on their new planet. Mountains can block air currents and seas can moisture air. Endorheic seas don't have constant shorelines and newly formed rivers will shape the world.
In some cases, it might be required to use bombs to blast a hole through a mountain range or to create a strait connecting two seas. In other cases, it will be required to make an isthmus between two continents to lower the tides. Geographical adjustments will have to be done. But they are not the biggest thread for a new planet.
Pioneers will have a major challenge with hydrology. If that planet never had liquids flowing on its surface, rivers will not be safe. We can imagine how a river will flow through a place with many craters. It will create a lot of lakes and will have a huge number of waterfalls. In some places, declivity will be too small and rivers will start to deposit sediments until they will separate into branches and eventually will change course. In other places, water will flow too rapidly and will erode the rocks. If erosion takes place at the walls of a crater that is flooded with water, it will be like collapsing a dam. A flood will occur along the river. Pioneers will have to take care of all these. They will need to blast away unstable natural barriers, to dig channels or build dams where required, in order to control the amount of sediments and limit erosion. On the other hand, if a river from an endorheic basin is diverted elsewhere, the sea it feeds will shrink, like it happened to Aral Sea by natural (in past) and artificial (today) ways.
While terraforming the planet, engineers will need a base on ground. Since the planet will undergo massive transformations, the base must be placed in the safest location.
After terraforming process Edit
Things will not end once the planet is terraformed. Putting water on a planet that had no rivers will result in long term changes. There will be 3 challenges for future generations:
- By adding a big weight (like an ocean), surface starts to change. This will generate earthquakes, volcanism and also the crust will sink a few meters. Even for a body without any molten core, the process will still create some compression force. The opposite effect will be on ex-glaciers. Since their water had moved to the oceans, the crust will be lighter and it will rise. This change will be faster in the first 10 years, but will slow down to less then 1 cm per Earth year after a century.
- On new formed rivers, erosion and sedimentation will keep on working until they will reach an equilibrium profile. As the process keeps on going, it is possible that huge areas will be affected. Settlers will have the duty to control this process.
- As geographic features change, climate will also change.
High mountains might be above layers of greenhouse gasses. In many cases, they will resemble conditions found before terraforming. We can imagine the huge volcanoes on Mars becoming reservations. Deep canyons will remain similar to what the deep oceanic falls on Earth.
Rivers will tend to reach an equilibrium profile, like on Earth, but they will never make it in a reasonable timeframe, like a human lifetime. This instability can be used. High erosion can create very tight canyons, very good for dams. Many waterfalls will still exist, resulting in an increase of electricity production. Could settlers turn their attention to hydro energy? they will need such facilities to control floods and stock water for agriculture, anyway. Having the advantage of large surfaces of uninhabited land, it will be easy for them to do get land for building.
As the population increases, the impact on the environment will grow. First settlers might only want to control a small river with dams and dikes, to farm on its proximity, but future generations will bring with them new ideas and new development plans.
By not understanding the strong link between geographic features and terraforming, engineers will have major faults, that can stop the entire process. On the other hand, by directing the forces of nature in a correct way, it will be more easy to make another planet or moon a better home for our future generations.