The program initializes to the parameters of present day Mars. To determine environmental conditions after terraforming, modify these parameters within Realistic Ranges (outlined below) and then click on Calculate.

To return the applet to the default setting of present day Mars, click on Reset.

If you switch Caps and Regolith on or off then be sure to press Reset afterwards.

Input.

To operate this program you have to enter or modify four parameters.

1) Albedo. This represents the reflectivity of Mars which is nominally set at 0.2. A smaller value indicates a darker planet, whilst a higher value indicates a more reflective planet.

Here are some values to guide your input:

No albedo value outside the range 0 - 1 makes any sense. Values between 0.1 - 0.3 are most realistic when considering Martian terraforming.

2) Insolation Factor. This represents addtional sunlight reflected onto Mars from orbiting mirrors, hence increasing the planet's insolation. Thus, for a ten percent increase in insolation, type in an Insolation Factor of 1.1. An Insolation Factor of 2.3 would give Mars the equivalent insolation of the Earth. Current mirror concepts might be described by an Insolation Factor between 1.01 - 1.3, except for the dynamically supported magnifying soletta design of Birch which would have an IF between 1.2 - 2.3. The default setting is 1. Realistic range: 1 - 2.3.

3) CO2 Pressure. The partial pressure of carbon dioxide must be entered in bars (roughly, 1 bar = 1 atmosphere). The default setting of 6 millibars is therefore 0.006. Scenarios which rely primarily on a CO2 greenhouse usually invoke between 1 - 2 bars of CO2 being released from surface reservoirs. These days more "conservative" values of 0.2 - 0.5 bars seem more prevalent. Carbon dioxide is toxic for humans above 0.01 bar and so if you wish to simulate a fully terraformed Mars (with a background nitrogen/oxygen atmosphere) you must lower the CO2 Pressure to this value and increase other warming methods. Note, if the caps/regolith are switched on then you do not need to manually adjust CO2 Pressure. Realistic Range: 0 - 3.

4) N2/O2 Pressure. Nitrogen and oxygen add to the overall pressure of the atmosphere. They do not have a greenhouse effect of their own but can cause pressure broadening of absorption bands, hence enhancing the greenhouse effects of other gases. Enter values in bars. Realistic Range: 0 - 3.

5) CH4 Pressure. It is possible that small amounts of methane might be made on Mars, or imported from comets, for the purposes of terraforming. Enter values in millionths of a bar (microbars). Realistic Range: 0 - 50000.

6) NH3 Pressure. It is possible that small amounts of ammonia might be made on Mars, or imported from comets, for the purposes of terraforming. One modelEnter values in millionths of a bar (microbars). Realistic Range: 0 - 100.

7) CFC Pressure. The term "CFC" is used as a blanket term to describe powerful trace greenhouse gases manufactured to absorb in the infrared window region. (In reality, they are likely to be a mix of perfluorocarbons rather than CFCs.) Their pressure must be entered in millionths of a bar (microbars) and values typically considered for use in terraforming are between 0.01 - 10 microbars. the default setting is 0. Realistic Range: 0 - 10.

The following input is only required when Caps and Regolith is switched on. On pressing Reset, the program defaults to a 350 mbar CO2 climate model with 3.6 mbar in the atmosphere, 46.4 mbar in the polar caps, 300 mbar in the regolith and a Td of 30 K..

8) Cap CO2 Inventory. This indicates the pressure equivalent of CO2 ice stored in the polar caps. It will thus respond to climate change. Most estimates place the CO2 stored in the polar caps as a meagre 10 mbar but some models of CO2 ice or clathrate beneath the surface of the North Polar Cap estimate the amount as high as a whopping 850 mbar. Enter values in millibars. Realistic Range: 1 - 100.

9) Regolith Td. This is the the temperature rise required to outgas 1/e of the regolith CO2 inventory. It is therefore easier to extract copious CO2 from the regolith if Td is low. Models have examined the behaviour of regoliths over a Td range of 10-60 K and have concluded that low values are likely to be unrealistic. Realistic Range: 30 - 60.

10) Regolith CO2 Capacity. This is the maximum holding capacity of the Regolith for adsorbed CO2. Models vary widely between 40-2000 mbar, but recent work definitely favours lower estimates. Enter values in millibars. Realistic Range: 40 - 500.

11) Regolith CO2. This is the actual quantity of CO2 adsorbed in the regolith. Since calculations start off from low temperatures, it is best to initially assume that the regolith is fully charged with CO2 and thus to set Regolith CO2 the same as Regolith CO2 Capacity. Realistic Range: 40 - 500.

Output.

The program will give three values as output: the Mean Global Surface Temperature; the Polar Temperature; and the Maximum Tropical Temperature. The latter two are rough approximations and should not be taken too seriously.

The program initializes with a mean Global Surface Temperature for Mars of 218.6 K, or -54.4 celsius. By comparison, the mean Global Surface Temperature of the Earth is about 288 K, or 15 celsius.

Delta T is the warming increment and is the same in degrees C or degrees K. Here, it is equal to the Mean Global Surface Temperature minus the Black Body temperature of Mars.

Planet frozen above latitude refers to the latitude poleward of which the temperature is below freezing.

Habitable percent of surface refers to the percentage area of Mars that is above freezing.

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