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The principle of Terraforming in Aurora is based on changing the atmosphere in order to alter the environment of the planet so it is suitable for your species.

The actual mechanics of using terraforming in the game interface are relatively straightforward. If you have any terraforming installations on a planet or any ships with terraforming modules in orbit, go to the Environment tab, select the gas you want and check the Add Gas checkbox if you want to add the gas rather than remove it. Terraforming installations can be built by industrial capacity and transported to a different planet with freighters.

A Terraforming Ship is easy to design. Copy your freighter design, remove the cargo holds and cargo handling systems and add a Terraforming Module (or perhaps two). If you don't yet have Terraforming module tech, you can research it using the Research tab of the Economics window. It is under Construction / Production.

The Basics

Our own atmosphere has a variety of gases but only Nitrogen, Oxygen and Argon are 1% or above. Everything else is in tiny amounts. Aurora only bothers with the major gases in a planetary atmosphere so planets will generally start with no more than three gases in their atmosphere. Open up the Economics window and take a look at the Environment tab for Earth. The list of gases in the Atmospheric Data section shows the following information:

Nitrogen 79% 0.79 atm
Oxygen 20% 0.2 atm
Argon 1% 0.01 atm
Total Atmospheric Pressure: 1

This shows both the percentage of each gas in the atmosphere and the atmospheric pressure (atm) of each gas. As the atm amount is based on Earth's atmospheric pressure of 1, the atm figures match the percentages. Lets create a colony on Mars and compare this to its atmosphere. Open up the F9 System View window, which provides detailed information on every body in a star system (you can open this by pressing the orange sun icon at the middle top of the system map). It is useful to check this view every time you find a new system, just to see what types of planets you have found and their colony cost (more on colony cost later). If there is more than one star in the system, each star and any associated planets will be on a separate tab. If the System View is slow to load, switch to the options tab and select Hide Asteroids then switch back to the Sol-A tab. Select Mars and press the Add Colony button. Open the Economics window, or press Refresh All (middle bottom) if it is already open. You should see a new colony for Mars. Select it and take a look at the Environment tab. The atmospheric data shows:

Nitrogen 70% 0.007 atm
Carbon Dioxide 30% 0.003 atm
Total Atmospheric Pressure: 0.01

The atmospheric pressure on Mars is only about 1% of that on Earth so the atm figures are tiny. In effect, Mars has almost no atmosphere at all. The atmospheric pressure on Venus is about 100x greater than on Earth and 10,000x greater than Mars.

Each species in Aurora has environmental tolerances with their midpoint being their homeworld. The habitability of planets will vary considerably depending on the species tolerances so a world that is ideal for humans may be uninhabitable for some other species and vice versa. Way back in Part 1 of the tutorial, covering game creation, we entered some values in the Species Tolerance section of the New Game window to set these values for human. As a reminder, those were a maximum deviation in oxygen pressure of 50%, a max deviation in gravity of 70%, a max deviation in temperature of 22 and a max atmospheric pressure to 4.

Fortunately you don't have to remember those as you can find them in the top right of the F9 System View Window. Open it up and take a look. The section is called Environmental Tolerances. The first item is a dropdown showing the selected species while the second shows which gas that species can breathe. You can have methane breathers in Aurora in which case every reference to oxygen in this tutorial would read as methane. There are four rows below this showing the min/max for gravity, oxygen and temperature and the max for pressure. If you are playing through this tutorial from the start, those values should show that an ideal habitable world for humans will have a temperature between -10 and 38C, an oxygen pressure between 0.1 and 0.3 atm, a gravity between 0.1G and 1.9G and a maximum atmospheric pressure of 4.0 atm.

Atmospheric Gases


Gas Toxicity (for oxygen-breathing races) Greenhouse Effect
Hydrogen Colony cost 2 None
Helium None None
Methane Colony cost 2 Warming
Ammonia Colony cost 2 None
Water None None
Neon None None
Nitrogen None None
Carbon Monoxide Colony cost 2 None
Nitrogen Oxide Colony cost 2 None
Oxygen None/Colony cost 2(if >30% concentration) None
Hydrogen Sulphide Colony cost 2 None
Argon None None
Carbon Dioxide None Warming
Nitrogen Dioxide Colony cost 2 Warming
Sulphur Dioxide Colony cost 2 Warming
Chlorine Colony cost 3 None
Fluorine Colony cost 3 None
Bromine Colony cost 3 None
Iodine Colony cost 2 None
Safe Greenhouse Gas None Warming
Anti-Greenhouse Gas None Cooling


C# Aurora makes some minor changes to the gas table. The safe greenhouse gas is now named Aestusium, and the safe anti-greenhouse gas is now named Frigusium. Carbon Dioxide is now a dangerous gas in sufficient quantity.

Dangerous gases now have safe concentration levels. These levels are percentages of the body's atmosphere, not absolute pressure values. For example, a planet with with 0.001 atm of CO2 and no other gases will have a dangerous atmosphere, because the CO2 is 100% of the planet's atmosphere, even though the absolute amount is low.

Finally, if a planet's temperature is low enough, gases will freeze out of the atmosphere. This is most important for water vapour, since planetary water balance is much more important in C#. Note that for water in particular, the boiling point is set much lower than water's actual boiling point, because water will evaporate and condense based on temperature. -18 Celsius is the point where some parts of the planet are warm enough to have some water evaporation.

Gas Toxicity (for oxygen-breathing races) Boiling Point Greenhouse Effect
Hydrogen Colony cost 2 (safe level 500 ppm = 0.05%) 20K = -253C None
Helium None 4K = -269C None
Methane Colony cost 2 (safe level 30,000 ppm = 30% for methane-breathers, 500 ppm = 0.05% for oxygen-breathers) 109K = -164C Warming
Ammonia Colony cost 2 (safe level 50 ppm = 0.005%) 240K = -23C None
Water None 245K = -18C None
Neon None 27K = -246C None
Nitrogen None 77K = -196C None
Carbon Monoxide Colony cost 2 (safe level 50 ppm = 0.005%) 82K = -191C None
Nitrogen Oxide Colony cost 2 (safe level 5 ppm = 0.0005%) 121K = -152C None
Oxygen Colony cost 2 (safe level 30,000 ppm = 30% for oxygen-breathers, 500 ppm = 0.05% for methane-breathers) 90K = -183C None
Hydrogen Sulphide Colony cost 2 (safe level 20 ppm = 0.002%) 212K = -61C None
Argon None 87K = -186C None
Carbon Dioxide Colony cost 2 (safe level 5,000 ppm = 0.5%) 195K = -78C Warming
Nitrogen Dioxide Colony cost 2 (safe level 5 ppm = 0.0005%) 262K = -11C Warming
Sulphur Dioxide Colony cost 2 (safe level 5 ppm = 0.0005%) 263K = -10C Warming
Chlorine Colony cost 3 (safe level 1 ppm = 0.0001%) 239K = -34C None
Fluorine Colony cost 3 (safe level 1 ppm = 0.0001%) 85K = -188C None
Bromine Colony cost 3 (safe level 1 ppm = 0.0001%) 332K = 59C None
Iodine Colony cost 2 (safe level 1 ppm = 0.0001%) 457K = 184C None
Aestusium None 100K = -173C Warming
Frigusium None 1K = -272C Cooling

Colony Cost and Terraforming

In addition to the individual species tolerances, the requirements for an ideal habitable world are no dangerous gases such as Chlorine or Hydrogen Sulphide and a maximum oxygen percentage of 30%. A planet that doesn't meet the gravity criterion is uninhabitable and there is nothing you can do about that. Falling outside one or more of the other criteria means the planet will have a colony cost above zero.

The colony cost measures the amount of Infrastructure required to support the population. The formula for required infrastructure is Population in millions x Colony Cost x 100. So a population of one million on a planet with a colony cost of 2 would need 200 infrastructure. A population of 15 million on a population with a colony cost of 0.8 would need 15 x 0.8 x 100 = 1200 infrastructure. If there is insufficient infrastructure for the population there will be negative growth, with the percentage based on how bad the shortage is, as well as unrest. You don't need to remember the formula as the Population & Production summary shows the maximum population for the available infrastructure.

Note that you can put ground bases, troops, sensors etc. on any world except a gas giant, regardless of the habitability. If you want an actual population though, which you will need to run shipyards, factories, etc., then the planet has to be habitable or at least have enough infrastructure for the inhabitants.

Note that Underground Infrastructure and Orbital Habitat Modules can be used to colonize even uninhabitable comets.

The colony cost is calculated in the following way. The five checks below this paragraph are made. Whichever results in the highest colony cost, that will be the colony cost for the planet. You can see these factors in the Colony Cost Factors section in the lower left of the F9 view for the currently selected planet.

  1. ) If the atmosphere is not breathable, the colony cost is 2.0.
  2. ) If there are toxic gases in the atmosphere then the colony cost will be 2.0 for some gases and 3.0 for others. (See above)
  3. ) If the pressure is too high, the colony cost will be equal to the Atmospheric Pressure divided by the species maximum pressure with a minimum of 2.0
  4. ) If the oxygen percentage is above 30%, the colony cost will be 2.0
  5. ) The colony cost for a temperature outside the range is Temperature Difference / Temperature Deviation. So if the deviation was 22 and the temperature was 48 degrees below the minimum, the colony cost would be 48/22 = 2.18

In the case of Mars, the gravity is OK, the atmosphere is not breathable, there are no toxic gases, the pressure is not too high, there is no oxygen and the temperature is too low. Therefore, the colony cost will either be 2.0 for the lack of a breathable atmosphere or the colony cost for the temperature differential, whichever is higher. Assuming the temperature colony cost was 2.18, which would also be the colony cost for Mars, the best way to start terraforming would be to warm up the planet until the temperature colony cost was less than 2.0, at which point the lack of a breathable atmosphere would became the main issue and you could start adding oxygen. Once the atmosphere was breathable, you would go back to worrying about temperature.

Terraforming Installations

Terraformers can add or remove a small amount of a selected gas over time. The amount added is measured in atmospheric pressure (atm). Note that as you add atm for one gas, the percentages of the different gases in the atmosphere will change. A single terraforming module or single terraforming installation with basic tech can add 0.001 atm per year. In other words, it could generate Earth's atmosphere in about 1000 years. That can be improved by researching the racial terraforming rate and by building more terraformers.

Mars and Venus are both hard to terraform because their atmospheric pressure is so different to Earth's. Mars essentially has no atmosphere and you have to start almost from scratch. The first thing you need to do to make an atmosphere breathable is to ensure the atm of oxygen in the atmosphere falls within your species' tolerance for Oxygen. Assuming the tutorial values for human tolerances, on Mars you would need to create enough oxygen to get the oxygen atm to 0.1, which for one terraformer at the basic tech level of 0.001 per annum will take 100 years. If you had twenty terraformers though, it would only take five years. Increasing the Terraforming rate to 0.002 would halve the time. As you may have guessed, terraforming requires a considerable investment of time and resources.

So you get the 0.1 atm of oxygen into the Martian atmosphere. Is it breathable? Unfortunately not, because pure oxygen atmospheres are a bad idea. Apart from the unfortunate consequences of striking a match, breathing pure oxygen over long periods causes lung damage. So an atmosphere in Aurora is not breathable unless the oxygen content is 30% or less. So if we need at least 0.1 atm of oxygen and that can't be more than 30% of the total atmospheric pressure, what does that total atmospheric pressure need to be? 0.1 * 100/30 = 0.333, so we need a total atm of 0.334 or another 0.234 atm, which will take another 234 years for the lonely terraformer. This can be any non-Toxic gas. Nitrogen is a reasonable choice or if you also need to change the temperature too, either up or down, you can use a greenhouse gas or an anti-greenhouse gas. For Mars, Carbon Dioxide would be ideal, although you could also use the abstract Safe Greenhouse Gas.

Temperature and Greenhouse Gases

As you add or subtract any type of gas to/from the atmosphere, the atmosphere will be updated and that will also affect the temperature. Every system body has a base temperature and a surface temperature. The base temperature is based on the solar infall from the star (or stars in binary systems) while the surface temperature includes adjustments for atmosphere and planetary albedo (which is the reflectivity of the surface). The formulas used are shown on the Environment tab of the Economics window

Surface Temperature in Kelvin = Base Temperature in Kelvin x Greenhouse Factor x Albedo
Greenhouse Factor = 1 + (Atmospheric Pressure / 10) + Greenhouse Pressure (Maximum = 3.0)

So every gas adds a little to the greenhouse factor but greenhouse gases add 10x as much. You get other benefits from warming as well. If the hydrosphere for a planet is Ice Sheet rather than Liquid Water (check the F9 view again), then at a certain point the ice will melt and form oceans. This will change the albedo because the ice that was reflecting heat back into space just melted and you will see a jump in temperature. The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

As the pressure increases, you will see the percentages of different gases changing. If there is enough oxygen in terms of atm then once the oxygen percentage drops below 30%, the atmosphere will be breathable.

Changes in C# 1.12.0

In C# 1.12.0 dust was added to the calculation and the formulas were changed to the following to prevent anti-greenhouse gas from creating temperatures below absolute zero (previously anti-greenhouse pressure was subtracted from greenhouse pressure):

Greenhouse Factor =  1 + (Atmospheric Pressure / 10) + Greenhouse Pressure (Maximum = 3)
Anti-Greenhouse Factor =  1 + (Dust Level / 20000) + Anti-Greenhouse Pressure (Maximum = 3)
Surface Temperature (K)  = (Base Temperature (K) * Greenhouse Factor * Albedo) / Anti-Greenhouse Factor

Atmospheric Pressure

Venus is almost impossible to terraform in Aurora. Each species has a maximum atmospheric pressure (Check F9 again to see yours). Before anything else, you would need to reduce Venus below that point. Assuming your species tolerance is about 4 atm then reducing the Venusian atmosphere, which has a pressure for 100, to that level would take our solo terraformer 96,000 years

You best bet for terraforming is to find a planet where the conditions are much closer to those on Earth. For example, you might find one with the right temperature and sufficient atmospheric pressure but the oxygen atm is 0.08 instead of the required 0.1 (or whatever your min oxygen atm tolerance is). Making this atmosphere breathable would involve adding just 0.02 atm of oxygen, which would take the solo terraformer 20 years, or 1 year for 20 terraformers. Equally, a planet with an already breathable atmosphere that is a little too hot or too cold can be made ideal by adding/subtracting greenhouse gases or adding anti-greenhouse gas.

Dangerous Gases

Another consideration is Dangerous gases. An atmosphere will never be breathable if it contains gases such as Bromine, Chlorine, Sulphur Dioxide, Methane, Ammonia, Fluorine, Carbon Monoxide, Nitrogen Oxide, Hydrogen Sulphide, etc. All these will have to be extracted from the atmosphere by your terraformers

Terraformers as Weapons

Terraformers can even be used as weapons. If you found a planet where you wanted to loot the industry but you didn't want to bombard or invade, you could slowly extract the oxygen from the atmosphere.

Terraforming Difficult Worlds

The above guide names Venus as almost impossible, due to the amount of pressure it has. However, it is only almost impossible. If you're dead-set at terraforming it legitimately, rather than using SpaceMaster Mode - perhaps to take advantage of the huge stores of minerals that might have been found there - it not only possible, but practical.

Let's review the ways you can terraform:

Terraforming Installations

Terraforming installations are perhaps the least efficient way to go about it, because they require substantial manpower on-site in order to function. On a planet like Venus, not only will this require incredible amounts of Infrastructure, but most likely nearly all of the imported colonists will be working day and night to keep themselves alive in the extremely hostile environment - very few, if any, will be left to man the terraforming installations.

Terraforming installations are additionally five times the size of terraforming modules (125k tons vs 25k tons), meaning it's rather difficult to move them around; in the case of Venus, this in not a big issue, since it's close to Earth, but the logistics become terrible if the Venusian-type planet is extrasolar. To top it all off, they're more expensive in terms of resources (300 duranium and boronide vs 250 each).

In conclusion: Avoid using installations whenever possible.

Terraforming Modules on ships

Putting modules on ships is overall a better option than terraforming installations. However, there are some limitations to this practice.

One is the fuel use - unless you've got tens of millions tons of Sorium deposits in yoru home system, chances are that your fuel reserves are not infinite, and a fleet of terraformers is going to use a lot of fuel moving around. Another, perhaps more serious one, is that terraforming modules are still big things, and require fairly massive Shipyards - or very many moderately-sized shipyards with lots of slipways, which would incidentally exacerbate the fuel problem. Still, they will work with just 100 crew manning them each, rather than 250k civilians, and can be more easily moved.

In conclusion: Better than terraforming installations, but not ideal.

Terraforming Modules on PDCs

Now we're getting places. PDCs have some advantages and some disadvantages, compared to ships.

PDCs can be prefabbed, which is how you should produce them if you plan to deploy them on another world, which allows you to make them with Industry instead of shipyards. Typically, this will mean that they can be made in greater amounts and with greater alacrity than ships. Moving the prefab components will be less of a hassle than moving installations (since they'll be smaller), and they will work without civilian manufacturers manning them. Unfortunately, you will have to assemble them on-site, which can be a problem - but one easily solved with the use of a Construction Brigade or ten.

The major disadvantage of PDCs is that you can't move them once they're deployed. Once you build a PDC, it's there to stay. Currently, there doesn't seem to be much point in destroying them, either.

In conclusion: Might be worthwhile for a long-term project like Venus, but unfortunately not reusable.

Terraforming Modules on Orbitals

What if you could combine the reusability of ship-based modules and the ability of being produced by industry of PDCs? This is what Orbital Habitats have to offer. Ships with an Orbital Habitat Module are classed as an Orbital Habitat, and can therefore be built by Industry (not prefabbed, though) instead of Shipyards.

Put one Orbital Habitat Module on your design, and as many Terraforming Modules as you want. Orbital Habitat Modules are pretty big, and are essentially an overhead cost of building these Terraforming Stations with Industry - so put many Terraforming Modules on each, no less than 10. 50 or even 100 each would not be wrong.

Since putting engines and fuel on these beasts is a fool's game, you will need tugs. Large ones - an easy method of designing appropriate towing vessels is to copy the terraforming station design, and put engines on until you reach a reasonable speed, then remove the orbital habitat and terraforming modules. You will be left with a design that is much smaller, and capable of reasonably towing the habitat to its destination.

In conclusion: This is currently the preferred way to terraform difficult worlds, taking the minimum amount of time and resources.