Essay on Terraforming

Definition

Terraforming: the process of changing an alien planet or moons' atmosphere, ocean and climate closer to that of current day Earth, so that humans might colonise it.

Examines the limitations of terraforming, in terms of the gravity, day length, & year length of the planet of interest. Goes on to examine the proposed methods for achieving terraforming, including chemistry, biology & molecular nanotechnology. Then goes on to outline the conclusions that can be drawn from this critique.

Limitations

Gravity

The planet must have a gravitational pull at its surface roughly equivalent to the one we evolved in, which produces a downward acceleration of approximately 9.8 m/s² or 1 G.

* Represents the average acceleration (1) at the surface of the planet (2).

1. There are many factors which affect this, two of the most important would be the size & mass of the planet.
2. This is taken to be the upper atmosphere for the gas giants. Neither current theory nor observation can exactly pin down where the surface is!

Too Little

If the gravitational pull is too small, human muscles atrophy and the entire skeletal structure loses mass, strength and resilience.

This is fine if you intend never to leave. I've heard this suggested as a 'retirement village' concept for the aged and infirm, but I believe that after a short period in which the body would flourish due to increased blood flow, the heart itself would become weaker and their health would degenerate faster .

In the 'too little' category would be planets Mars, Mercury and Pluto (the surprise here being that both Mercury and Pluto have larger G forces at the surface than Mars). Our moon, as well as the major moons Ganymede, Callisto, Titan and Triton all have smaller surface gravity's still. All asteroids and comets have minimal gravitational fields.

A possible solution to a lack of gravity would be to adapt a technique demonstrated in the movie '2001, A Space Odyssey', in which an artificial gravity is maintained by centripetal acceleration. This might be in the form of a conventional toroidal space station or centripetal vivarium.

A centripetel structure in orbit can receive light continuously, but one on a planetary surface is locked into the same day length as the rock itself.

Besides, centripetal designs work best when the structures are in free-fall (orbit). When they are built in a gravity well (a planet surface), you need to angle the walls away from full vertical so that the combination of centripetal force due to rotation and existing gravitational acceleration, produce a total force close to 1G. For a structure of any length you would need to 'step' the surface continuously and join the angled surfaces together, failing to do this would cause a continuously changing force on the occupants as they moved from one end to the other.

Too Much

If the gravitational pull is too large, humans are crushed by the forces. Our muscles, skeleton and heart were all shaped by the gravitational stresses of Earth.

We could probably get used to Neptune's 1.1 G's, but Jupiter's 2.3 would be strictly for body builders who wanted an alternative to steroids.

While centripetal acceleration could compensate for a gravity which is too small, there is no scientific theory known to mankind that suggests we would be able to compensate for excessive acceleration.

Day Length

The period and direction of rotation of a planet determines the time taken between successive 'sunrises'. Earth's day length is very close to 24 hours at this stage in its history (it's slowing down). Day length's of other solar planets range from less than half a day for Jupiter and Saturn, to more than 240 days for Venus.

The natural rhythms of Earth organisms, from plants and animals to humans, are locked into our immediate environment.

Plants help regulate growth and flowering by the changing rhythms of light they experience. Plants seem to adapt to the available lighting conditions within limits, though different cycles of day length may cause unwanted effects such as early flowering of crops.

Animals have natural rhythms of chemicals that induce restorative sleep (or at least slow down) each 24 hours. Animals will tend to follow a cycle of activity-rest close to 24 hours long even when exposed to constant light. Studies performed on humans suggest that while we can operate on different day lengths, forcing ourselves to do so causes significant psychological stress. I feel the majority of animals would be affected the same way, perhaps to an even greater degree.

The only hope for our teraformers is to create an artificial environment in which the light waxes and wanes each 24 hours.

This limits the usefulness of terraforming. You're going to all this effort to make a planet like Earth, yet the 'day' on the planet surface doesn't correspond to the 'day' in your colony.

Year Length

As a planet orbits the sun, it's spin axis remains pointed in the same direction (like a top). Because no planet's spin axis is perpendicular to it's axis of rotation about the sun, it alternately points one hemisphere then the other toward the sun. This causes the seasonal variations in such things as the length of daylight, ambient temperature and weather patterns.

Planets progressively further from the sun have a longer year length. Year length varies from as little as 88 days for Mercury to almost 12 years by the time you reach Jupiter.

Though Venus and Mars are closer to Earth at 0.62 and 1.88 years respectively, even such variations from the natural seasonal lengths of Earth would cause pregnant animals to birth at the wrong time and crops to mature at an unnatural (and perhaps undesirable) rate.

This leads to the same inherent result as the day-length being wrong, but now added to the fact that you're clocks won't tell you if it's day or night outside, you're calendar won't even warn you whether you need to wear warm clothes.

It would be easier to survive in a glass dome on the bottom of the ocean, and the oceans are much closer.

Methods

Chemistry

Dump chemicals into the planet to neutralise or lock up the unwanted or excessive chemicals and boost any useful ones that are lacking.

Microbiology

If you have a suitable mixture of initial elements in the atmosphere, but they are just locked up in the 'wrong compounds', it might be possible to find or genetically engineer a simple organism that feeds on the compounds you don't want, to produce those you do.

Nanotechnology

Produce a billion (or so) little machines to do the work for you. This method could be suitable for 'wrong compound' atmospheres. If the machines are small enough to work at a molecular level and can grab individual molecules of reactant and shunt their atoms around to form new connections and compounds, they may be more efficient than living organisms.

Conclusion

For the huge amount of effort required to produce an inferior imitation of Earth, potential colonists could have built many space based colonies with an ideal environment.

Space colonies have continuous access to sunshine. Day length and seasonal variations can be altered easily, by adjusting mirrors that reflect light down to the inner surfaces of the colony.

The effort required to adjust the atmospheric chemical balances on a planetary scale would be better spent on space colonies as well. Planetary atmospheres can be many kilometers deep, yet you would only require up to a few kilometers of air between the floor and ceiling of even the largest space colonies.

Energy would be needed to bring materials from the surface of planets and moons into orbit in order to build space colonies, but much of the heavier elements (metals etc.) required are abundant in the asteroid belt, so obtaining them should not be difficult.

The only reason humans would set up a base on a planet is the need to study the planet itself. Our computers are becoming more powerful and capable all the time, and automation of many tasks done by humans will be further spurred by the harsh conditions. Mining and other materials collection operations will be largely automated.

Terraforming alien and hostile planets is a romantic fantasy that will never be realised.

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