This is a simulation of what one would expect to find on a terraformed Callisto, using formulas from Math And Terraforming. Please note that not even the supercomputers at NASA can provide us with a perfect simulation. The information showed here is only an approximation.
Basic data[]
- Distance from Sun: 778.57 million km
- Distance to Jupiter: 1.883 million km
- Diameter: 4821 km
- Solar Constant: 0.073
- Mass: 0.018 Earths
- Mean density: 1.834 kg/l
- Orbital period: 16.689 Earth days
- Jupiter's orbital period: 11.862 Earth years
- Rotation axial tilt: below 10 degrees
Atmosphere[]
Callisto is at a safe distance from Jupiter. Its Hill sphere is larger and perturbations from other moons and Jupiter itself are not so strong. This will ensure a more stable atmosphere.
During this simulation, we will use an atmosphere with the same pressure at sea level as Earth's and a similar composition.
- Atmosphere stability for oxygen molecules:
- Earth's gravity (15 degrees C): 4.116
- Callisto's gravity (15 degrees C): 18.87
- Callisto's gravity (-100 degrees C): 11.34
- Atmosphere stability for water molecules:
- Earth's gravity (15 degrees C): 7.320
- Callisto's gravity (15 degrees C): 33.54
- Callisto's gravity (-100 degrees C): 20.16
- Atmosphere stability for hydrogen molecules:
- Earth's gravity (15 degrees C): 65.88
- Callisto's gravity (15 degrees C): 301.9
- Callisto's gravity (-100 degrees C): 181.4
notes: A value below 10 means stability for over a million years, a value between 10 and 100 means stability between 0.1 and 10 millions of years, while a value higher then 100 means stability for less then 10 thousand years.
This calculation does not include solar wind erosion.
Conclusion: Callisto will not have a safe atmosphere for long, but can hold one that will remain breathable for maybe 10 thousand years. Water vapors will ascend fast below the greenhouse layer. Above the greenhouse shield, they will cool fast and freeze, producing water ice clouds, that will mostly condensate and fall back to the surface.
Ionizing UV radiation, even if weak, will break water molecules and will free hydrogen, which will fast escape into space. This process can replenish oxygen, but will consume water.
The atmosphere will look like this:
Ground average temperature: 15 degrees C
- Surface pressure at sea level: 1
- Atmosphere total mass (Earth = 1): 1.08
- Atmosphere breathable height: 63.2 km
- Atmosphere total height: 188 km
Ground average temperature: -100 degrees C
- Surface pressure at sea level: 1
- Atmosphere total mass (Earth = 1): 0.84
- Atmosphere breathable height: 48.8 km
- Atmosphere total height: 145 km
Combined: Atmosphere total mass (Earth = 1): 0.96 Atmosphere breathable height: 55 km
- Atmosphere total height: 160 km.
Basically, there will be two different atmospheric layers: below and above the greenhouse gasses. The lower layer will be hotter and will contain most of the air, while the upper layer will be cold and will compress the lower layer.
The atmosphere will be fluffy.
Temperature[]
Main article: Temperature.
The first problem with Calisto is that we need to gain the correct surface temperature. The Solar Constant is low (0.073), compared to Earth (1.98). Greenhouse Gases are needed. The Greenhouse Calculator provides us with some useful values. The needed amount of sulfur hexafluoride is 0.189 kg/sqm.
Climate Simulation[]
Main article: Climate.
On Earth, the average temperature is +15 degrees C. By using greenhouse gasses we will try the best to get a similar value.
Callisto has a smaller diameter then Earth (0.378), a thing that will help air currents mix temperatures. The extremely fluffy atmosphere also helps us maintain a global temperature similar for the whole moon.
Average temperatures for each latitude:
- poles: 12 C
- 75 deg: 14 C
- 60 deg: 15 C
- 45 deg: 16 C
- 30 deg: 16 C
- 15 deg: 17 C
- equator: 17 C
Day - night cycle variation:
Callisto has a long day (16.689 Earth days). Because of this and the huge greenhouse effect needed, there will be little differences in temperature.
- Daily temperature variation: 8 degrees C
- Equator day-night variations: 13 to 21 degrees C
- Near pole day-night variations: 8 to 16 degrees C.
Altitude:
Because of the fluffy atmosphere, temperature will not decrease significantly with altitude.
Seasons:
Callisto has a very small axial tilt, so there will be no seasons.
Conclusion.
Callisto is very interesting. It behaves like an Outer Planet, but, the climate will experience some changes. The long rotation period which triggers a long day-night cycle appears to stimulate some changes. It brings a difference of 8 degrees C between day and night. Because of this, the atmosphere will heat in day time. This will cause the air to hold less humidity. During night, temperature will drop and it will be possible to rain. Also, there will be little temperature variations between equator and poles. This will stimulate some winds to blow.
From all four Galilean moons, Callisto will have the best climate for humans. It will be like a mild spring, with small periods of increasing temperature and periods of diffuse rains.
Geography[]
See also: Geography and Geographic Pattern - Craters.
Callisto is a dead object. It has no volcanic activity. Its core appears to be cold and undifferentiated. With other words, this moon is made of a mixture of rocks and ices that alternate down to its center. Terraforming such an object will be a difficult task. If terraformers will decide to heat-up the atmosphere, then ices will start to melt. Since liquid water is heavier then ice, it will slowly make its way down towards the core, just like moulons erode a glacier. This process will take much time.
Callisto appears to be a perfect candidate for partial Ground Insulation. In that case, ices will be covered with a protective insulation, while rocks with a higher melting point will not. This will ensure many Geographic features will remain.
Continents vs oceans. Unfortunately, we don't have an altitude map revealing Callisto's surface, so we don't know clearly how the moon will look like. So, we don't know if it will have a global ocean or many endorheic basins, a global or many continents or if it will be composed of a mixture of land and water, like the Moon.
Callisto is dominated by craters (see Geographic Pattern - Craters). In that case, altitude variation is significant, like on Mercury or the Moon. So, Callisto might behave like a Mountain Planet. On the other hand, the atmosphere is high enough to pass over obstacles.
One thing is clear: there will be many lakes, islands and peninsulas, from the former craters. Rivers will have many waterfalls on their ways.
The Sky[]
As one can see above, the atmosphere of Callisto will be fluffy. Clouds and hazes will block visibility most of time. Still, there is a higher chance for settlers to see blue sky.
Still, assuming sky visibility similar to Earth, one will see the following celestial bodies:
- The Sun - 1.79 units
- Jupiter - 74.25 units
- Io - 1.58 to 2.48 units
- Europa - 1.22 to 2.58 units
- Ganymede - 1.78 to 6.47 units.
Amalthea would be visible at about 3.6 magnitude, and Himalia, when its pericenter is in opposition from the sun, would be visible at a dim 5.4.
All other Jovian moons would not be visible from Callisto,
To see how large a celestial body will look like, draw a circle of X mm on a sheet of paper and look at it from a distance of 1 m.
- Mercury: 3.2 to 3.6 magnitude
- Venus: 0.2 to 0.8 magnitude
- Earth: 1.3 to 2.2 magnitude
- Moon: 5.2 to >6 magnitude
- Mars: 4.2 to 5.5 magnitude
- Saturn: 1.2 to 3.8 magnitude
Human Colonies[]
- Population limit: 26.5 million
- Land population feeding capacity: 11 people fed from one square km
- Largest city supported by environment: 106 000 people
Assuming it will have similar types of terrain Earth will have, Europa can support a Population Limit of 26.5 million people.
As showed above, Callisto has the best climate from all Galilean moons. This will stimulate people to settle here.
Industry[]
Since Callisto has the best climate, there is a higher chance that people will like to settle here. Major industrial complexes will move to other moons, letting here those industries that don't harm too much the environment.
Some energy can be gathered from waterfalls, but most will come from nuclear power plants.
Agriculture[]
Callisto is far from the Sun. Because of this, plants don't get enough light to grow like on Earth. Still, settlers will have to produce the food they need to eat. Experiments made with grain crops showed that at Jupiter's orbit, it is possible to grow and harvest cereals (see Plants on new worlds and Agriculture for details).
Transportation[]
Callisto has no volcanic activity and probably no quakes. So, it is a good place to build infrastructure. Roads and railways will have to pass through many obstacles like crater rims.
Air transport will have a significant importance.
As for now, it is not known how future continents and oceans will look and if water transportation can have a significant importance.
Orbits around the moon appear to be stable for enough time. A network of satellites can provide the background for telecommunications. It is impossible to launch a satellite into a geosynchronous orbit, so there will be many satellites orbiting the moon.
There will be one or more bases on the surface, that will be used for spaceships. Most interplanetary ships will dock at Himalia, while cargo and passengers will be transshipped to and from Ganymede by smaller ships.
Tourism[]
With less gravity and a mild climate, Callisto will be a good destination for people who suffer from many heart, circulatory and respiratory diseases.
Also, since a significant part of the landscape will remain thanks to ground insulation, Callisto will be a wonderful place, with many lakes, mountains and waterfalls.
Wild Life[]
Callisto, with its climate patterns, is suitable for most plants and animals found on Earth in temperate regions.
The moon, like all celestial bodies who have their Geography dominated by craters, will have many islands and landlocked seas. These features are ideal for separating ecosystems. Many endangered Earth species can be protected here.