Planetary engineering

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Planetary engineering is the development and application of technology for the purpose of influencing the environment of a planet. Planetary engineering encompasses a variety of methods such as terraforming, seeding, and geoengineering.

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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 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

Projected temperature and precipitation changes relative to preindustrial; end-of-century response without (a) and with (b) geoengineering to avoid temperature rise above 1.5C. SRMtemperature-projections.jpg
Projected temperature and precipitation changes relative to preindustrial; end-of-century response without (a) and with (b) geoengineering to avoid temperature rise above 1.5C.
A theoretical design for a power station on Mars. Terraforming designs are not yet planned. Terraforming of Mars.jpg
A theoretical design for a power station on Mars. Terraforming designs are not yet planned.

Terraforming is the process of modifying the atmosphere, temperature, surface topography or ecology 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". [2] 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. [2]

NASA has defined categories of habitability systems and technologies for terraforming to be feasible. [3] 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. [3]

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. [4] 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 CO2 for sufficient atmospheric change is present within Mars' polar deposits, and liquid CO2 could only be present at warmer temperatures "deep within the crust". [4] 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. [4] 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. [5] 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. [5] 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. [5]

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. [6] 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. [7] 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. [8] Through this ethical framework, terraforming attempts on these planets could be seen to threaten their intrinsically valuable environments, rendering these efforts unethical. [6]

Seeding

NASA's Hubble Space Telescope took the picture of Mars on June 26, 2001, when Mars was approximately 68 million kilometers (43 million miles) from Earth -- the closest Mars has ever been to Earth since 1988. Hubble can see details as small as 16 kilometers (10 miles) across. The colors have been carefully balanced to give a realistic view of Mars' hues as they might appear through a telescope. Especially striking is the large amount of seasonal dust storm activity seen in this image. One large storm system is churning high above the northern polar cap (top of image), and a smaller dust storm cloud can be seen nearby. Another large dust storm is spilling out of the giant Hellas impact basin in the Southern Hemisphere (lower right) exploration. Mars Hubble.jpg
NASA's Hubble Space Telescope took the picture of Mars on June 26, 2001, when Mars was approximately 68 million kilometers (43 million miles) from Earth — the closest Mars has ever been to Earth since 1988. Hubble can see details as small as 16 kilometers (10 miles) across. The colors have been carefully balanced to give a realistic view of Mars' hues as they might appear through a telescope. Especially striking is the large amount of seasonal dust storm activity seen in this image. One large storm system is churning high above the northern polar cap (top of image), and a smaller dust storm cloud can be seen nearby. Another large dust storm is spilling out of the giant Hellas impact basin in the Southern Hemisphere (lower right) exploration.

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. [10]

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 CO2 present in the Martian atmosphere. [10] Later organisms such as multicellular plants must be able to withstand the freezing temperatures, withstand high CO2 levels, and produce significant amounts of O2.

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. [11]

Geoengineering

Impression of the hypothetical phrases of the terraforming of Mars MarsTransitionV.jpg
Impression of the hypothetical phrases of the terraforming of Mars

Geoengineering, or climate engineering, 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. [12] Examples of geoengineering are carbon dioxide removal (CDR), which removes carbon dioxide from the atmosphere, and the use of space mirrors to reflect solar energy to space. [12] [13] Carbon dioxide removal (CDR) has multiple practices, the simplest being reforestation, to more complex processes such as direct air capture. [12] [14] The latter is rather difficult to deploy on an industrial scale, for high costs and substantial energy usage would be some aspects to address. [12]

Another geoengineering discipline is solar radiation management (SRM), which is the process of rapidly cooling down the Earth's temperature. [12] Examples of this process include stimulating the cooling effect of volcanoes and enhancing the reflectivity of marine clouds. [12] When a volcano erupts, small particles known as aerosols proliferate throughout the atmosphere, reflecting the sun's energy back into space. [12] [15] This results in a cooling effect, and humanity could conceivably inject these aerosols into the stratosphere, spurring large-scale cooling. [12] [15]

Visible ship tracks in the Northern Pacific, on 4 March 2009. On an overcast day, the clouds look uniform. However, NASA MODIS images' sensor reveals long, skinny trails of brighter clouds hidden within. As ships travel across the ocean, pollution in the ships' exhaust create more cloud drops that are smaller in size, resulting in even brighter clouds. ShipTracks.jpg
Visible ship tracks in the Northern Pacific, on 4 March 2009. On an overcast day, the clouds look uniform. However, NASA MODIS images' sensor reveals long, skinny trails of brighter clouds hidden within. As ships travel across the ocean, pollution in the ships' exhaust create more cloud drops that are smaller in size, resulting in even brighter clouds.

Marine cloud brightening (MCB) is a solar radiation management theory that is designed to make marine clouds brighter, reflecting light back into deep space. [16] By reflecting light from the sun, this process could help offset anthropogenic global warming, which threatens the lives of all human beings and life on Earth. [17] One proposal involves spraying a vapor into low-laying sea clouds, creating more cloud condensation nuclei. [18] This would in theory result in the cloud becoming whiter, and reflecting light more efficiently. [18]

See also

Related Research Articles

<span class="mw-page-title-main">Greenhouse effect</span> Atmospheric phenomenon causing planetary warming

The greenhouse effect occurs when greenhouse gases in a planet's atmosphere cause some of the heat radiated from the planet's surface to build up at the planet's surface. This process happens because stars emit shortwave radiation that passes through greenhouse gases, but planets emit longwave radiation that is partly absorbed by greenhouse gases. That difference reduces the rate at which a planet can cool off in response to being warmed by its host star. Adding to greenhouse gases further reduces the rate a planet emits radiation to space, raising its average surface temperature.

<span class="mw-page-title-main">Terraforming</span> Hypothetical planetary engineering process

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 make it habitable for humans to live on.

<span class="mw-page-title-main">Atmosphere</span> Layer of gases surrounding an astronomical body held by gravity

An atmosphere is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules.

Climate engineering is a term used for both carbon dioxide removal and solar radiation management, also called solar geoengineering, when applied at a planetary scale. However, they have very different geophysical characteristics which is why the Intergovernmental Panel on Climate Change no longer uses this overarching term. Carbon dioxide removal approaches are part of climate change mitigation. Solar geoengineering involves reflecting some sunlight back to space. All forms of geoengineering are not a standalone solution to climate change, but need to be coupled with other forms of climate change mitigation. Another approach to geoengineering is to increase the Earth's thermal emittance through passive radiative cooling.

The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the Sun's output would be only 70 percent as intense during that epoch as it is during the modern epoch. The paradox is this: with the young sun's output at only 70 percent of its current output, early Earth would be expected to be completely frozen – but early Earth seems to have had liquid water and supported life.

<span class="mw-page-title-main">Planetary habitability</span> Known extent to which a planet is suitable for life

Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and maintain environments hospitable to life. Life may be generated directly on a planet or satellite endogenously or be transferred to it from another body, through a hypothetical process known as panspermia. Environments do not need to contain life to be considered habitable nor are accepted habitable zones (HZ) the only areas in which life might arise.

Atmospheric escape is the loss of planetary atmospheric gases to outer space. A number of different mechanisms can be responsible for atmospheric escape; these processes can be divided into thermal escape, non-thermal escape, and impact erosion. The relative importance of each loss process depends on the planet's escape velocity, its atmosphere composition, and its distance from its star. Escape occurs when molecular kinetic energy overcomes gravitational energy; in other words, a molecule can escape when it is moving faster than the escape velocity of its planet. Categorizing the rate of atmospheric escape in exoplanets is necessary to determining whether an atmosphere persists, and so the exoplanet's habitability and likelihood of life.

<span class="mw-page-title-main">Runaway greenhouse effect</span> Climatic effect causing a planets atmosphere to trap heat and prevent cooling

A runaway greenhouse effect occurs when a planet's atmosphere contains greenhouse gas in an amount sufficient to block thermal radiation from leaving the planet, preventing the planet from cooling and from having liquid water on its surface. A runaway version of the greenhouse effect can be defined by a limit on a planet's outgoing longwave radiation which is asymptotically reached due to higher surface temperatures evaporating water into the atmosphere, increasing its optical depth. This positive feedback means the planet cannot cool down through longwave radiation and continues to heat up until it can radiate outside of the absorption bands of the water vapour.

<span class="mw-page-title-main">Colonization of Venus</span> Proposed colonization of the planet Venus

The colonization of Venus has been a subject of many works of science fiction since before the dawn of spaceflight, and is still discussed from both a fictional and a scientific standpoint. However, with the discovery of Venus's extremely hostile surface environment, attention has largely shifted towards the colonization of the Moon and Mars instead, with proposals for Venus focused on habitats floating in the upper-middle atmosphere and on terraforming.

<span class="mw-page-title-main">Terraforming of Mars</span> Hypothetical modification of Mars into a habitable planet

The terraforming of Mars or the terraformation of Mars is a hypothetical procedure that would consist of a planetary engineering project or concurrent projects, with the goal to transform Mars from a planet hostile to terrestrial life to one that can sustainably host humans and other lifeforms free of protection or mediation. The process would involve the modification of the planet's extant climate, atmosphere, and surface through a variety of resource-intensive initiatives, and the installation of a novel ecological system or systems.

<span class="mw-page-title-main">Terraforming of Venus</span> Engineering the global environment of Venus to make it suitable for humans

The terraforming of Venus or the terraformation of Venus is the hypothetical process of engineering the global environment of the planet Venus in order to make it suitable for human habitation. Adjustments to the existing environment of Venus to support human life would require at least three major changes to the planet's atmosphere:

  1. Reducing Venus's surface temperature of 737 K
  2. Eliminating most of the planet's dense 9.2 MPa (91 atm) carbon dioxide and sulfur dioxide atmosphere via removal or conversion to some other form
  3. The addition of breathable oxygen to the atmosphere.
<span class="mw-page-title-main">Atmosphere of Venus</span> Gas layer surrounding Venus

The atmosphere of Venus is primarily of supercritical carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K, and the pressure is 93 bar (1,350 psi), roughly the pressure found 900 m (3,000 ft) underwater on Earth. The Venusian atmosphere supports opaque clouds of sulfuric acid, making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging. Aside from carbon dioxide, the other main component is nitrogen. Other chemical compounds are present only in trace amounts.

<span class="mw-page-title-main">Climate of Mars</span> Climate patterns of the terrestrial planet

The climate of Mars has been a topic of scientific curiosity for centuries, in part because it is the only terrestrial planet whose surface can be easily directly observed in detail from the Earth with help from a telescope.

This is a list of climate change topics.

<span class="mw-page-title-main">Solar geoengineering</span> Reflection of sunlight to reduce global warming

Solar geoengineering, or solar radiation modification (SRM), is a type of climate engineering in which sunlight would be reflected back to outer space to limit or offset human-caused climate change. There are multiple potential approaches, with stratospheric aerosol injection (SAI) being the most-studied method, followed by marine cloud brightening (MCB). Other methods have been proposed, including a variety of space-based approaches, but they are generally considered less viable, and are not taken seriously by the Intergovernmental Panel on Climate Change. SRM methods could have a rapid cooling effect on atmospheric temperature, but if the intervention were to suddenly stop for any reason, the cooling would soon stop as well. It is estimated that the cooling impact from SAI would cease 1–3 years after the last aerosol injection, while the impact from marine cloud brightening would disappear in just 10 days. Contrastingly, once any carbon dioxide is added to the atmosphere and not removed, its warming impact does not decrease for a century, and some of it will persist for hundreds to thousands of years. As such, solar geoengineering is not a substitute for reducing greenhouse gas emissions but would act as a temporary measure to limit warming while emissions of greenhouse gases are reduced and carbon dioxide is removed.

<span class="mw-page-title-main">Carbonate–silicate cycle</span> Geochemical transformation of silicate rocks

The carbonate–silicate geochemical cycle, also known as the inorganic carbon cycle, describes the long-term transformation of silicate rocks to carbonate rocks by weathering and sedimentation, and the transformation of carbonate rocks back into silicate rocks by metamorphism and volcanism. Carbon dioxide is removed from the atmosphere during burial of weathered minerals and returned to the atmosphere through volcanism. On million-year time scales, the carbonate-silicate cycle is a key factor in controlling Earth's climate because it regulates carbon dioxide levels and therefore global temperature.

<span class="mw-page-title-main">Bio-geoengineering</span> Form of climate engineering

Bio-geoengineering is a form of climate engineering which seeks to increase the solar reflectivity of crops by modifying physiological leaf and/or canopy traits to help reduce regional surface warming.

<span class="mw-page-title-main">Life on Venus</span> Scientific assessments on the microbial habitability of Venus

The possibility of life on Venus is a subject of interest in astrobiology due to Venus's proximity and similarities to Earth. To date, no definitive evidence has been found of past or present life there. In the early 1960s, studies conducted via spacecraft demonstrated that the current Venusian environment is extreme compared to Earth's. Studies continue to question whether life could have existed on the planet's surface before a runaway greenhouse effect took hold, and whether a relict biosphere could persist high in the modern Venusian atmosphere.

<span class="mw-page-title-main">Earth analog</span> Planet with environment similar to Earths

An Earth analog, also called an Earth analogue, Earth twin, or second Earth, is a planet or moon with environmental conditions similar to those found on Earth. The term Earth-like planet is also used, but this term may refer to any terrestrial planet.

<span class="mw-page-title-main">Planetary habitability in the Solar System</span> Habitability of the celestial bodies of the Solar System

Planetary habitability in the Solar System is the study that searches the possible existence of past or present extraterrestrial life in those celestial bodies. As exoplanets are too far away and can only be studied by indirect means, the celestial bodies in the Solar System allow for a much more detailed study: direct telescope observation, space probes, rovers and even human spaceflight.

References

  1. ↑ MacMartin, Douglas G.; Ricke, Katharine L.; Keith, David W. (13 May 2018). "Solar geoengineering as part of an overall strategy for meeting the 1.5°C Paris target". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 376 (2119): 20160454. Bibcode:2018RSPTA.37660454M. doi:10.1098/rsta.2016.0454. PMC   5897825 . PMID   29610384.
  2. 1 2 Pollack, James B.; Sagan, Carl (1993). "Planetary engineering" (PDF). In Lewis, John S.; Matthews, Mildred Shapley; Guerrieri, Mary L. (eds.). Resources of Near-Earth Space. University of Arizona Press. pp. 921–950. ISBN   978-0-8165-1404-5. Archived from the original (PDF) on 24 June 2010.
  3. 1 2 "Habitats, Habitability, and Human Factors". NASA SBIR & STTR Program. Archived from the original on 27 October 2021. Retrieved 5 November 2021.
  4. 1 2 3 Jakosky, Bruce M.; Edwards, Christopher S. (August 2018). "Inventory of CO2 available for terraforming Mars". Nature Astronomy. 2 (8): 634–639. Bibcode:2018NatAs...2..634J. doi:10.1038/s41550-018-0529-6. S2CID   133894463.
  5. 1 2 3 Fogg, M. J. (1987). "The Terraforming of Venus". Journal of the British Interplanetary Society. 40: 551–564. Bibcode:1987JBIS...40..551F.
  6. 1 2 "The Ethics of Terraforming | Issue 38". Philosophy Now. Archived from the original on 5 November 2021. Retrieved 5 November 2021.
  7. ↑ Sparrow, Robert (Fall 1999). "The Ethics of Terraforming" (PDF). Environmental Ethics. 21 (3): 227–245. doi:10.1007/978-90-481-9920-4_124 . Retrieved 21 April 2023.
  8. ↑ Sparrow, Robert (Fall 1999). "The Ethics of Terraforming" (PDF). Environmental Ethics. 21 (3): 227–245. doi:10.1007/978-90-481-9920-4_124 . Retrieved 21 April 2023.
  9. ↑ Lopez-Arreguin, A.J.R.; Montenegro, S. (September 2019). "Improving engineering models of terramechanics for planetary exploration". Results in Engineering. 3: 100027. doi: 10.1016/j.rineng.2019.100027 . S2CID   202783328.
  10. 1 2 Todd, Paul (August 2006). "Planetary biology and terraforming". Gravitational and Space Biology. 19 (2): 79–85. Gale   A176373142.
  11. ↑ Conde-Pueyo, Nuria; Vidiella, Blai; Sardanyés, Josep; Berdugo, Miguel; Maestre, Fernando T.; de Lorenzo, Victor; Solé, Ricard (9 February 2020). "Synthetic Biology for Terraformation Lessons from Mars, Earth, and the Microbiome". Life. 10 (2): 14. doi: 10.3390/life10020014 . PMC   7175242 . PMID   32050455.
  12. 1 2 3 4 5 6 7 8 "What is Climate Engineering?". Union of Concerned Scientists. Archived from the original on 27 October 2021. Retrieved 27 October 2021.
  13. ↑ "Explainer: Six ideas to limit global warming with solar geoengineering". Carbon Brief. 9 May 2018. Archived from the original on 1 November 2021. Retrieved 1 November 2021.
  14. ↑ "Effectively removing CO2 from the atmosphere". ScienceDaily. Archived from the original on 27 October 2021. Retrieved 27 October 2021.
  15. 1 2 "Volcanoes Can Affect Climate". USGS. Archived from the original on 31 October 2021. Retrieved 1 November 2021.
  16. ↑ "Marine Cloud Brightening (Technology Briefing)". Geoengineering Monitor. 15 April 2021. Retrieved 13 January 2023.
  17. ↑ Jackson, Randal. "The Effects of Climate Change". Climate Change: Vital Signs of the Planet. Archived from the original on 4 May 2020. Retrieved 3 November 2021.
  18. 1 2 "Proposed Geoengineering Technologies". Geoengineering Monitor. Archived from the original on 3 November 2021. Retrieved 3 November 2021.

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