Editing Terraforming (section)

===Aspects and definitions===
In 1985, [[Martyn Fogg]] started publishing several articles on terraforming. He also served as editor for a full issue on terraforming for the ''Journal of the British Interplanetary Society'' in 1992. In his book ''Terraforming: Engineering Planetary Environments'' (1995), Fogg proposed the following definitions for different aspects related to terraforming:<ref name="EPE" />

* [[Planetary engineering]]: the application of technology for the purpose of influencing the global properties of a planet.
* [[Climate engineering|Geoengineering]]: planetary engineering applied specifically to Earth. It includes only those macro engineering concepts that deal with the alteration of some global parameter, such as the greenhouse effect, atmospheric composition, [[insolation]] or impact flux.
* Terraforming: a process of planetary engineering, specifically directed at enhancing the capacity of an extraterrestrial planetary environment to support life as we know it. The ultimate achievement in terraforming would be to create an open planetary [[ecosystem]] emulating all the functions of the [[biosphere]] of Earth, one that would be fully habitable for human beings.

Fogg also devised definitions for candidate planets of varying degrees of human compatibility:<ref>Fogg, 1996</ref>

* Habitable planet (HP): A world with an environment sufficiently similar to Earth's as to allow comfortable and free human habitation.
* Biocompatible planet (BP): A planet possessing the necessary physical parameters for life to flourish on its surface. If initially lifeless, then such a world could host a [[biosphere]] of considerable complexity without the need for terraforming.
* Easily-terraformable planet (ETP): A planet that might be rendered biocompatible, or possibly habitable, and maintained so by modest planetary engineering techniques and with the limited resources of a starship or robot precursor mission.

Fogg suggests that [[Mars]] was a biologically compatible planet in its youth, but is not now in any of these three categories, because it can only be terraformed with greater difficulty.<ref>{{Cite book|title=Terraforming : engineering planetary environments|last=Fogg|first=Martyn J.|date=1995|publisher=Society of Automotive Engineers|isbn=1560916095|oclc=32348444}}</ref>