Introduction

Terraforming is the process of planetary engineering designed to expand a planet’s capacity for supporting terrestrial life. Originally coined by science fiction, terraforming has been adopted by science and is a subject of serious theoretical study.

Fogg (1995) defines terraforming as:

"A process of planetary engineering, specifically directed at enhancing the capacity of an extraterrestrial planetary environment to support life. The ultimate in terraforming would be to create an uncontained planetary biosphere emulating all the functions of the biosphere of the Earth — one that would be fully habitable for human beings."

Ecopoiesis

Much of the research in the scientific community focuses on the possibility of terraforming Mars, firstly allowing aerobic life such as humans.

The first stage of terraforming is known as oikoV, house, and poihsiV, or production. It is defined by Fogg 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.". The initial stage of planetary engineering leading to ecopoiesis has been the focus of most terraforming research.

To facilitate ecopoiesis on Mars, certain conditions must be produced:

1. The mean global surface temperature must be increased by around 60 K
2. The mass of the atmosphere must be increased
3. Liquid water must be made available
4. The surface UV and cosmic ray flux must be reduced

In order to allow plant roots to respirate, a low amount of free oxygen and nitrogen must also be produced before further terraforming can take place.

Terraforming an entire planet is a huge task, but the conditions above have the favourable properties that each is a catalyst for the others: for example, increasing the mass of the atmosphere increases its capacity to act as a radiation and meteor shield, enhances the greenhouse effect and thus raising the temperature, and widens the stability field of liquid water. Mars’s atmosphere may also have the potential to be "nudged" into a runaway CO₂ greenhouse effect, a climatic-feedback experienced to a lethally effective extreme on, for example, Venus.

Sagan predicted this effect may be achieved by reducing the albedo of the polar ice caps, effectively altering the planet’s sunlight absorption/reflection ratio. A subsequent NASA study in 1976 suggested such a darkening of the caps may not need to be huge: a reduction in albedo from 77% to 73%.

Pioneer Organisms

Initially, Mars — or other hostile planets — will only be capable of supporting certain types of microorganisms, such as the bacteria found in the most inhospitable environments on Earth: the extremophiles. Extremophiles on our planet have been found thriving in conditions that most other creatures would quickly die in, such as in high radiation environments, in rocks deep inside the Earth, or inside volanic vents on the ocean floor. Here we take a brief look at some possible candidates that may be capable of living, and multiplying, during the early stages of terraforming.

• Chroococcidiopsis sp: this hardy type of organic molecules instead of synthesis”>heterotrophic bacterium has an impressive resistance to UV and ionizing radiation, due to its multilayered cell wall, carotenoid pigments and super-efficient DNA repair mechanisms.

Other candidates

In addition to Mars, there are other candidates within our Solar System that may be suitable for terraforming: Venus, Titan, Mercury, Europa, Ganymede, Io, Callisto, and the Earth’s Moon. However, if Mars is a daunting challenge, terraforming any of these worlds would be on another level again, requiring technology and resources far beyond what humans currently have available.

The engineering of extrasolar worlds would truly be the final frontier of terraforming, if economical interstellar travel is ever achieved. As of this year (2005), astronomers have found 155 confirmed extrasolar planets across 136 star systems, with many more unconfirmed detections by the Hubble telescope. Of these, a handful are approaching a similar mass to that of our Earth, and as the precision of our detection methods improves we can only hope to find worlds that are better candidates for extrasolar terraforming.

References

1. Fogg, Martyn J., Terraforming Mars: A Review of Research
2. Pioneer Organisms Nominated for Terraforming
3. Extra-solar Planets Catalog