The different terraforming methods which will transform Mars into a second Earth are called 'Achievement Processes'. They try to achieve a chemical and biological equilibrium in the new biosphere on the surface of Mars.

When an equilibrium is created methods need to be devised which maintain the equilibrium. These 'Maintaining Processes' have so robust that Mars can still sustain life after millions of years, even without human influence.

First supergreenhouse gasses are used like CFC's. When the temperature rises frozen CO2 in the polar caps and in the frozen upper layers of the crust will sublimate into the atmosphere. This will dense the atmosphere even more resulting in another rise in the surface temperature, causing more CO2 to sublime.

This chain reaction only stops or slows down when all the CO2 has entered the atmosphere or when counter measures are taken like covering the polar caps with a layer of dust [Sagan, 1973]. Venus has a runaway greenhouse so this planet has to be terraformed the opposite way, possibly by using genetically engineered hyperthermophyle bacteria.

In the meantime the experimental sowing of genetically altered life on the surface of Mars can be implemented. This is called Ecopoiesis [Haynes, 1990], what is defined as "...the fabrication of an uncontained, anaerobic, biosphere on the surface of a sterile planet. As such, it can represent an end in itself or be the initial stage in a more lengthy process of terraforming." [Fogg, 1995].

Second Step Terraforming of Mars [2TM]:
This next step will be an enormous operation. The gasses in the thickened atmosphere have to be converted into a mixture comparable to Earth's atmosphere. To achieve this within human timescales enormous energy sources are needed. Nuclear fusion is the obvious choice for this. It could even be possible to use fusion directly to change carbon into nitrogen, an element not very abundant on Mars, but needed to create an Earth-like atmosphere.

Third Step Terraforming of Mars [3TM]:
Scientists know that the Earth is capable to sustain itself. The CO2 ends up in the ground through sedimentation and finds it's way back again into the atmosphere through volcanism. Cycles like these are common for a large amount of elements. For example there is an oxygencycle, a nitrogencycle, etc.

On Mars in her early youth cycles like these also played a role, but somehow they stopped. It is theorized that this happened because the inner energy motor of Mars died out. Earth's energy motor causes volcanism and thus the carbon cycle.

Almost all the CO2 became stored in the rocks which thinned the atmosphere creating a cold and dry planet. Mars also couldn't keep an atmosphere that large because of it's small size. Therefore gas also disappeared in space, aided by the solar wind. All together this is the reason that terraforming on the long term is a Maintaining Process.

The planet has to maintain itself without human influence. With Mars however this is impossible. Plate tectonics is needed for the carbon cycle and as said before the planet is to small to hold a thick atmosphere.

Therefore machines have to be built which sustain the chemical and maybe even the biological equilibrium. They work automatically and repair themselves so they can stay active for thousands and maybe even millions of years. Examples are:

1)	A selfregulating chain of machines between Mars and Titan which scoop nitrogen gas from the atmosphere of Titan and take it to Mars.
2)	A ring of superconducting material deep in the ground around the equator so an artificial magnetic field is created.
3)	A certain amount of machines interconnected on the surface of Mars which, with the use of feed back, maintain the equilibrium of the system. Is there too much CO2? Then they suck it out of the atmosphere and turn it into another gas or into calcite, a rock.
4)	Technology to 'turn on' a planet again, maybe by multiple meltdowns?

An other problem arises in the far future [millions of years from now] when weathering and erosion flattens the surface. Nothing will counter that, no mountains will form, eventually a well-balanced distribution of sediments will create a topographical flat surface. The beauty of the geology of Mars will disappear and this could be the ground for people leaving Mars. Mars as a living environment is then exhausted.