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Planetary engineering is the development and application of technology for the purpose of influencing the environment of a
planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
. Planetary engineering encompasses a variety of methods such as
terraforming Terraforming or terraformation ("Earth-shaping") is the hypothetical process of deliberately modifying the atmosphere, temperature, surface topography or ecology of a planet, moon, or other body to be similar to the environment of Earth to mak ...
, seeding, and geoengineering. Widely discussed in the scientific community, terraforming refers to the alteration of other planets to create a habitable environment for terrestrial life. Seeding refers to the introduction of life from
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
to habitable planets. Geoengineering refers to the engineering of a planet's climate, and has already been applied on Earth. Each of these methods are composed of varying approaches and possess differing levels of feasibility and ethical concern.


Terraforming

Terraforming is the process of modifying the
atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
,
temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
, surface topography or
ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...
of a planet, moon, or other body in order to replicate the environment of Earth.


Technologies

A common object of discussion on potential terraforming is the planet Mars. To terraform Mars, humans would need to create a new atmosphere, due to the planet's high carbon dioxide concentration and low atmospheric pressure. This would be possible by introducing more greenhouse gases to below "freezing point from indigenous materials". To terraform Venus, carbon dioxide would need to be converted to graphite since Venus receives twice as much sunlight as Earth. This process is only possible if the greenhouse effect is removed with the use of "high-altitude absorbing fine particles" or a sun shield, creating a more habitable Venus. NASA has defined categories of habitability systems and technologies for terraforming to be feasible. These topics include creating power-efficient systems for preserving and packaging  food for crews, preparing and cooking foods, dispensing water, and developing facilities for rest, trash and recycling, and areas for crew hygiene and rest.


Feasibility

A variety of planetary engineering challenges stand in the way of terraforming efforts. The atmospheric terraforming of Mars, for example, would require "significant quantities of gas" to be added to the Martian atmosphere. This gas has been thought to be stored in solid and liquid form within Mars' polar ice caps and underground reservoirs. It is unlikely, however, that enough for sufficient atmospheric change is present within Mars' polar deposits, and liquid could only be present at warmer temperatures "deep within the crust". Furthermore, sublimating the entire volume of Mars' polar caps would increase its current atmospheric pressure to 15 millibar, where an increase to around 1000 millibar would be required for habitability. For reference, Earth's average sea-level pressure is 1013.25 mbar. First formally proposed by astrophysicist Carl Sagan, the terraforming of Venus has since been discussed through methods such as organic molecule-induced carbon conversion, sun reflection, increasing planetary spin, and various chemical means. Due to the high presence of sulfuric acid and solar wind on Venus, which are harmful to organic environments, organic methods of carbon conversion have been found unfeasible. Other methods, such as solar shading, hydrogen bombardment, and magnesium-calcium bombardment are theoretically sound but would require large-scale resources and space technologies not yet available to humans.


Ethical considerations

While successful terraforming would allow life to prosper on other planets, philosophers have debated whether this practice is morally sound. Certain ethics experts suggest that planets like Mars hold an intrinsic value independent of their utility to humanity and should therefore be free from human interference. Also, some argue that through the steps that are necessary to make Mars habitable - such as fusion reactors, space-based solar-powered lasers, or spreading a thin layer of soot on Mars' polar ice caps - would deteriorate the current aesthetic value that Mars possesses. This calls into question humanity's intrinsic ethical and moral values, as it raises the question of whether humanity is willing to eradicate the current ecosystem of another planet for their benefit. Through this ethical framework, terraforming attempts on these planets could be seen to threaten their intrinsically valuable environments, rendering these efforts unethical.


Seeding


Environmental considerations

Mars is the primary subject of discussion for seeding. Locations for seeding are chosen based on atmospheric temperature, air pressure, existence of harmful radiation, and availability of natural resources, such as water and other compounds essential to terrestrial life.


Developing microorganisms for seeding

Natural or engineered microorganisms must be created or discovered that can withstand the harsh environments of Mars. The first organisms used must be able to survive exposure to ionizing radiation and the high concentration of present in the Martian atmosphere. Later organisms such as multicellular plants must be able to withstand the freezing temperatures, withstand high levels, and produce significant amounts of . Microorganisms provide significant advantages over non-biological mechanisms. They are self-replicating, negating the needs to either transport or manufacture large machinery to the surface of Mars. They can also perform complicated chemical reactions with little maintenance to realize planet-scale terraforming.


Climate engineering

Climate engineering Geoengineering (also known as climate engineering or climate intervention) is the deliberate large-scale interventions in the Earth’s climate system intended to counteract human-caused climate change. The term commonly encompasses two broad cate ...
is a form of planetary engineering which involves the process of deliberate and large-scale alteration of the Earth's climate system to combat climate change. Examples of geoengineering are carbon dioxide removal (CDR), which removes carbon dioxide from the atmosphere, and solar radiation modification (SRM) to reflect solar energy to space.
Carbon dioxide removal Carbon dioxide removal (CDR) is a process in which carbon dioxide () is removed from the atmosphere by deliberate human activities and durably stored in geological, terrestrial, or ocean reservoirs, or in products.IPCC, 2021:Annex VII: Glossar ...
(CDR) has multiple practices, the simplest being
reforestation Reforestation is the practice of restoring previously existing forests and woodlands that have been destroyed or damaged. The prior forest destruction might have happened through deforestation, clearcutting or wildfires. Three important purpose ...
, to more complex processes such as direct air capture. The latter is rather difficult to deploy on an industrial scale, for high costs and substantial energy usage would be some aspects to address. Examples of SRM include stratospheric aerosol injection (SAI) and marine cloud brightening (MCB). When a volcano erupts, small particles known as
aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be generated from natural or Human impact on the environment, human causes. The term ''aerosol'' co ...
s proliferate throughout the atmosphere, reflecting the sun's energy back into space. This results in a cooling effect, and humanity could conceivably inject these aerosols into the stratosphere, spurring large-scale cooling. One proposal for MCB involves spraying a vapor into low-laying sea clouds, creating more cloud condensation nuclei. This would in theory result in the cloud becoming whiter, and reflecting light more efficiently.


See also

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Astroengineering Engineering on an astronomical scale, or astronomical engineering, ''i.e.'', engineering involving operations with whole astronomical objects (planets, stars, etc.), is a known theme in science fiction, as well as a matter of recent scientific r ...
*
Macro-engineering In engineering, macro-engineering (alternatively known as mega engineering) is the implementation of large-scale design projects. It can be seen as a branch of civil engineering or structural engineering applied on a large landmass. In particular ...
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Megascale engineering Megascale engineering (or macro-engineering) is a form of exploratory engineering concerned with the construction of structures on an enormous scale. Typically these structures are at least in length—in other words, at least one megameter, hen ...
* Moving the Earth * Virgin Earth Challenge


References


Further reading

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External links


Geoengineering: A Worldchanging Retrospective
– Overview of articles on geoengineering from the sustainability site
Worldchanging Worldchanging was a nonprofit online publisher that operated from 2003 to 2010. Its strapline was ''A bright green future''. It published newsletters and books about sustainability, bright green environmentalism, futurism and social innovatio ...
{{DEFAULTSORT:Planetary engineering Space colonization Engineering disciplines