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Terraforming or terraformation ("Earth-shaping") is the
hypothetical A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obser ...
process of deliberately modifying the
atmosphere 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 ...
,
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
, surface
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sc ...
or
ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...
of a
planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
,
moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
, or other body to be similar to the environment of
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
to make it habitable for humans to live on. The concept of terraforming developed from both
science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...
and actual
science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence ...
.
Carl Sagan Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on ex ...
, an
astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
, proposed the
planetary engineering 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. Widely ...
of
Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
in 1961, which is considered one of the first accounts of the concept. The term was coined by
Jack Williamson John Stewart Williamson (April 29, 1908 – November 10, 2006), who wrote as Jack Williamson, was an American science fiction writer, often called the "Dean of Science Fiction". He is also credited with one of the first uses of the term ''genet ...
in a science-fiction short story ("
Collision Orbit The ''Seetee'' series is a science fiction series by American writer Jack Williamson (writing under the pseudonym "Will Stewart.") It consists of several books and stories set in the late 22nd century, amid space-dwelling Asteroid Belt miners who ...
") published in 1942 in ''
Astounding Science Fiction ''Analog Science Fiction and Fact'' is an American science fiction magazine published under various titles since 1930. Originally titled ''Astounding Stories of Super-Science'', the first issue was dated January 1930, published by William C ...
'', although
terraforming in popular culture Terraforming is well represented in contemporary literature, usually in the form of science fiction, as well as in popular culture.. While many stories involving interstellar travel feature planets already suited to habitation by humans and supp ...
may predate this work. Even if the environment of a planet could be altered deliberately, the feasibility of creating an unconstrained planetary environment that mimics Earth on another planet has yet to be verified. While Venus,
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
,
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
, and even the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
have been studied in relation to the subject, Mars is usually considered to be the most likely candidate for terraforming. Much study has been done concerning the possibility of heating the planet and altering its atmosphere, and
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
has even hosted debates on the subject. Several potential methods for the terraforming of Mars may be within humanity's technological capabilities, but according to Martin Beech, the economic attitude of preferring short-term profits over long-term investments will not support a terraforming project. The long timescales and practicality of terraforming are also the subject of debate. As the subject has gained traction, research has expanded to other possibilities including biological terraforming, para-terraforming, and modifying humans to better suit the environments of
planets A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a youn ...
and
moons A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...
. Despite this, questions still remain in areas relating to the
ethics Ethics or moral philosophy is a branch of philosophy that "involves systematizing, defending, and recommending concepts of right and wrong behavior".''Internet Encyclopedia of Philosophy'' The field of ethics, along with aesthetics, concer ...
,
logistics Logistics is generally the detailed organization and implementation of a complex operation. In a general business sense, logistics manages the flow of goods between the point of origin and the point of consumption to meet the requirements of ...
,
economics Economics () is the social science that studies the production, distribution, and consumption of goods and services. Economics focuses on the behaviour and interactions of economic agents and how economies work. Microeconomics anal ...
,
politics Politics (from , ) is the set of activities that are associated with making decisions in groups, or other forms of power relations among individuals, such as the distribution of resources or status. The branch of social science that studies ...
, and
methodology In its most common sense, methodology is the study of research methods. However, the term can also refer to the methods themselves or to the philosophical discussion of associated background assumptions. A method is a structured procedure for br ...
of altering the environment of an extraterrestrial world, presenting issues to the implementation of the concept.


History of scholarly study

The astronomer
Carl Sagan Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on ex ...
proposed the
planetary engineering 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. Widely ...
of Venus in an article published in the journal ''
Science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence ...
'' in 1961. Sagan imagined seeding the atmosphere of
Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
with
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...
, which would convert water, nitrogen and carbon dioxide into
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
s. As this process removed
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
from the atmosphere, the
greenhouse effect The greenhouse effect is a process that occurs when energy from a planet's host star goes through the planet's atmosphere and heats the planet's surface, but greenhouse gases in the atmosphere prevent some of the heat from returning directly ...
would be reduced until surface temperatures dropped to "comfortable" levels. The resulting carbon, Sagan supposed, would be incinerated by the high surface temperatures of Venus, and thus be sequestered in the form of "graphite or some involatile form of carbon" on the planet's surface.Sagan 1997, pp. 276–7. However, later discoveries about the conditions on
Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
made this particular approach impossible. One problem is that the clouds of Venus are composed of a highly concentrated
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...
solution. Even if atmospheric algae could thrive in the hostile environment of Venus's upper atmosphere, an even more insurmountable problem is that its atmosphere is simply far too thick—the high atmospheric pressure would result in an "atmosphere of nearly pure molecular oxygen" and cause the planet's surface to be thickly covered in fine graphite powder. This volatile combination could not be sustained through time. Any carbon that was fixed in organic form would be liberated as carbon dioxide again through combustion, "short-circuiting" the terraforming process. Sagan also visualized making
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
habitable for human life in "Planetary Engineering on Mars" (1973), an article published in the journal ''
Icarus In Greek mythology, Icarus (; grc, Ἴκαρος, Íkaros, ) was the son of the master craftsman Daedalus, the architect of the labyrinth of Crete. After Theseus, king of Athens and enemy of Minos, escaped from the labyrinth, King Minos sus ...
''. Three years later, NASA addressed the issue of planetary engineering officially in a study, but used the term "planetary ecosynthesis" instead. The study concluded that it was possible for Mars to support life and be made into a habitable planet. The first conference session on terraforming, then referred to as "Planetary Modeling", was organized that same year. In March 1979, NASA engineer and author
James Oberg James Edward Oberg (born November 7, 1944) is an American space journalist and historian, regarded as an expert on the Russian and Chinese space programs. He had a 22-year career as a space engineer in NASA specializing in orbital rendezvous. O ...
organized the First Terraforming Colloquium, a special session at the Lunar and Planetary Science Conference in Houston. Oberg popularized the terraforming concepts discussed at the colloquium to the general public in his book ''New Earths'' (1981). Not until 1982 was the word ''terraforming'' used in the title of a published journal article. Planetologist Christopher McKay wrote "Terraforming Mars", a paper for the '' Journal of the British Interplanetary Society''. The paper discussed the prospects of a self-regulating Martian biosphere, and the word "terraforming" has since become the preferred term. In 1984,
James Lovelock James Ephraim Lovelock (26 July 1919 – 26 July 2022) was an English independent scientist, environmentalist and futurist. He is best known for proposing the Gaia hypothesis, which postulates that the Earth functions as a self-regulating sy ...
and Michael Allaby published ''The Greening of Mars''. Lovelock's book was one of the first to describe a novel method of warming Mars, where
chlorofluorocarbon Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and p ...
s (CFCs) are added to the atmosphere. Motivated by Lovelock's book, biophysicist Robert Haynes worked behind the scenes to promote terraforming, and contributed the
neologism A neologism Ancient_Greek.html"_;"title="_from_Ancient_Greek">Greek_νέο-_''néo''(="new")_and_λόγος_/''lógos''_meaning_"speech,_utterance"is_a_relatively_recent_or_isolated_term,_word,_or_phrase_that_may_be_in_the_process_of_entering_com ...
''Ecopoiesis'', forming the word from the Greek , ''oikos'', "house", and , ''poiesis'', "production". Ecopoiesis refers to the ''origin of an ecosystem''. In the context of space exploration, Haynes describes ecopoiesis as the "fabrication of a sustainable ecosystem on a currently lifeless, sterile planet". Fogg defines ecopoiesis as a type of
planetary engineering 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. Widely ...
and is one of the first stages of terraformation. This primary stage of ecosystem creation is usually restricted to the initial seeding of microbial life. A 2019 opinion piece by Lopez, Peixoto and Rosado has reintroduced microbiology as a necessary component of any possible colonization strategy based on the principles of microbial symbiosis and their beneficial ecosystem services. As conditions approach that of Earth, plant life could be brought in, and this will accelerate the production of oxygen, theoretically making the planet eventually able to support animal life.


Aspects and definitions

In 1985, Martyn J. 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: *
Planetary engineering 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. Widely ...
: the application of technology for the purpose of influencing the global properties of a planet. * 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 Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ...
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 An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
emulating all the functions of the
biosphere The biosphere (from Greek βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all ecosystems. It can also ...
of Earth, one that would be fully habitable for human beings. Fogg also devised definitions for candidate planets of varying degrees of human compatibility: * 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 The biosphere (from Greek βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all ecosystems. It can also ...
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 Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
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.


Habitability requirements

An absolute requirement for life is an energy source, but the notion of planetary habitability implies that many other geophysical, geochemical, and astrophysical criteria must be met before the surface of an astronomical body is able to support life. Of particular interest is the set of factors that has sustained complex, multicellular animals in addition to simpler organisms on Earth. Research and theory in this regard is a component of
planetary science Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth), celestial bodies (such as moons, asteroids, comets) and planetary systems (in particular those of the Solar System) and the processes of their ...
and the emerging discipline of
astrobiology Astrobiology, and the related field of exobiology, is an interdisciplinary scientific field that studies the origins, early evolution, distribution, and future of life in the universe. Astrobiology is the multidisciplinary field that invest ...
. In its astrobiology roadmap,
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
has defined the principal habitability criteria as "extended regions of liquid water, conditions favorable for the assembly of complex
organic molecule In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
s, and energy sources to sustain
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ...
."


Preliminary stages

Once conditions become more suitable for
life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energy ...
of the
introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...
, the importation of
microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
life could begin. As conditions approach that of Earth, plant life could also be brought in. This would accelerate the production of oxygen, which theoretically would make the planet eventually able to support
animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...
life.


Prospective targets


Mars

In many respects,
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
is the most Earth-like planet in the Solar System. It is thought that Mars once had a more Earth-like environment early in its history, with a thicker atmosphere and abundant water that was lost over the course of hundreds of millions of years. The exact mechanism of this loss is still unclear, though three mechanisms, in particular, seem likely: First, whenever surface water is present,
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
() reacts with rocks to form
carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate ...
s, thus drawing atmosphere off and binding it to the planetary surface. On Earth, this process is counteracted when
plate tectonics Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of larg ...
works to cause volcanic eruptions that vent carbon dioxide back to the atmosphere. On Mars, the lack of such tectonic activity worked to prevent the recycling of gases locked up in sediments.Forget, Costard & Lognonné 2007, pp. 80–2. Second, the lack of a
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior d ...
around Mars may have allowed the
solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
to gradually erode the atmosphere.
Convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...
within the core of Mars, which is made mostly of
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
, originally generated a
magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
. However the
dynamo "Dynamo Electric Machine" (end view, partly section, ) A dynamo is an electrical generator that creates direct current using a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundati ...
ceased to function long ago, and the magnetic field of Mars has largely disappeared, probably due to "loss of core heat, solidification of most of the core, and/or changes in the mantle convection regime." Results from the NASA MAVEN mission show that the atmosphere is removed primarily due to Coronal Mass Ejection events, where outbursts of high-velocity protons from the Sun impact the atmosphere. Mars does still retain a limited
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior d ...
that covers approximately 40% of its surface. Rather than uniformly covering and protecting the atmosphere from solar wind, however, the magnetic field takes the form of a collection of smaller, umbrella-shaped fields, mainly clustered together around the planet's southern hemisphere.Solar Wind, 2008 Finally, between approximately 4.1 and 3.8 billion years ago,
asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...
impacts during the Late Heavy Bombardment caused significant changes to the surface environment of objects in the Solar System. The low
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
of Mars suggests that these impacts could have ejected much of the Martian atmosphere into deep space.Forget, Costard & Lognonné 2007, pp. 80. Terraforming Mars would entail two major interlaced changes: building the atmosphere and heating it. A thicker atmosphere of greenhouse gases such as
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
would trap incoming
solar radiation Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ...
. Because the raised temperature would add greenhouse gases to the atmosphere, the two processes would augment each other. Carbon dioxide alone would not suffice to sustain a temperature above the freezing point of water, so a mixture of specialized greenhouse molecules might be manufactured.


Venus

Terraforming
Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
requires two major changes: removing most of the planet's dense carbon dioxide atmosphere, and reducing the planet's surface temperature. These goals are closely interrelated because Venus's extreme temperature may result from the
greenhouse effect The greenhouse effect is a process that occurs when energy from a planet's host star goes through the planet's atmosphere and heats the planet's surface, but greenhouse gases in the atmosphere prevent some of the heat from returning directly ...
caused by its dense atmosphere.


Mercury

Although usually disregarded as being too hot, Mercury may in fact be one of the easiest bodies in the solar system to terraform. Mercury's magnetic field is only 1.1% that of Earth's but it is thought that Mercury's magnetic field should be much stronger, up to 30% of Earth's, if it weren't being suppressed by certain solar wind effects. It is thought that Mercury's magnetic field was suppressed after "stalling" at some point in the past (possibly caused by the Caloris basin impact) and, if given a temporary "helping hand" by shielding Mercury from solar wind by placing an artificial magnetic shield at Mercury-Sun L1 (similar to the proposal for Mars), then Mercury's magnetic field would "inflate" and grow in intensity 30 times stronger at which point Mercury's magnetic field would be self sustaining provided the field wasn't made to "stall" by another celestial event. Despite being much smaller than Mars, Mercury has a gravity nearly identical in strength to Mars due to its increased density and could, with a now augmented
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior d ...
, hold a
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
/
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
atmosphere 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 ...
for millions of years. To provide this atmosphere, 3.5×1017
kilogram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...
s of water could be delivered by a similar process as proposed for Venus by launching a stream of kinetic impactors at Hyperion (the moon of Saturn) causing it to be ejected and flung into the inner solar system. Once this water has been delivered, Mercury could be covered in a thin layer of doped
titanium dioxide Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. It is a white solid that is insolu ...
photo-catalyst dust which would split the water into its constituent
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
and
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
molecules, with the hydrogen rapidly being lost to space and a 0.2-0.3
bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar * Chocolate bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a layer of cloud * Bar ( ...
atmosphere of pure oxygen being left behind in less than 70 years (assuming an efficiency of 30-40%). At this point the atmosphere would be breathable and
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
may be added as required to allow for plant growth in the presence of
nitrate Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insolu ...
s. Temperature management may not be required, despite an equilibrium average temperature of ~159 Celsius. Millions of square kilometers at the poles have an average temperature of 0-50 Celsius, or 32-122 Fahrenheit (an area the size of Mexico at each pole with habitable temperatures). The total habitable area is likely to be even larger given that the previously mentioned photo-catalyst dust would raise the albedo from 0.12 to ~0.6, lowering the global average temperature to tens of degrees and potentially increasing the habitable area. The temperature could be further managed with the usage of solar shades. Mercury has the potential to be the fastest celestial body to terraform at least partially, giving it a thin but breathable atmosphere with human-survivable pressures, a strong magnetic field, with at least a small percentage of its land at survivable temperatures at closer to the north and south poles provided water content could be constrained to avoid a runaway greenhouse effect.


Moon

Although the gravity on Earth's
moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
is too low to hold an atmosphere for geological spans of time, if given one, it would retain it for spans of time that are long compared to human lifespans. Landis and others have thus proposed that it could be feasible to terraform the moon, although not all agree with that proposal. Landis estimates that a 1 PSI atmosphere of pure oxygen on the moon would require on the order of two hundred trillion tons of oxygen, and suggests it could be produced by reducing the oxygen from an amount of lunar rock equivalent to a cube about fifty kilometers on an edge. Alternatively, he suggests that the water content of "fifty to a hundred comets" the size of Halley's comet would do the job, "assuming that the water doesn't splash away when the comets hit the moon." Likewise, Benford calculates that terraforming the moon would require "about 100 comets the size of Halley's."


Earth

It has been recently proposed that due to the effects of
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
, an interventionist program might be designed to return
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
to pre-industrial climate parameters. In order to achieve this, multiple solutions have been proposed, such as the management of
solar radiation Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ...
, the sequestration of carbon dioxide using geoengineering methods, and the design and release of climate altering genetically engineered organisms.


Other bodies in the Solar System

Other possible candidates for terraforming (possibly only partial or paraterraforming) include large moons of Jupiter or Saturn (
Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...
, Callisto, Ganymede,
Europa Europa may refer to: Places * Europe * Europa (Roman province), a province within the Diocese of Thrace * Europa (Seville Metro), Seville, Spain; a station on the Seville Metro * Europa City, Paris, France; a planned development * Europa Clif ...
,
Enceladus Enceladus is the sixth-largest moon of Saturn (19th largest in the Solar System). It is about in diameter, about a tenth of that of Saturn's largest moon, Titan. Enceladus is mostly covered by fresh, clean ice, making it one of the most refle ...
), and the dwarf planet Ceres.


Other possibilities


Biological terraforming

Many proposals for planetary engineering involve the use of genetically engineered bacteria. As synthetic biology matures over the coming decades it may become possible to build designer organisms from scratch that directly manufacture desired products efficiently. Lisa Nip, Ph.D. candidate at the MIT Media Lab's Molecular Machines group, said that by synthetic biology, scientists could genetically engineer humans, plants and bacteria to create Earth-like conditions on another planet. Gary King, microbiologist at
Louisiana State University Louisiana State University (officially Louisiana State University and Agricultural and Mechanical College, commonly referred to as LSU) is a public land-grant research university in Baton Rouge, Louisiana. The university was founded in 1860 n ...
studying the most extreme organisms on Earth, notes that "synthetic biology has given us a remarkable toolkit that can be used to manufacture new kinds of organisms specially suited for the systems we want to plan for" and outlines the prospects for terraforming, saying "we'll want to investigate our chosen microbes, find the genes that code for the survival and terraforming properties that we want (like radiation and drought resistance), and then use that knowledge to genetically engineer specifically Martian-designed microbes". He sees the project's biggest bottleneck in the ability to genetically tweak and tailor the right microbes, estimating that this hurdle could take "a decade or more" to be solved. He also notes that it would be best to develop "not a single kind of microbe but a suite of several that work together".
DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the A ...
is researching the use of photosynthesizing plants, bacteria, and algae grown directly on the Mars surface that could warm up and thicken its atmosphere. In 2015 the agency and some of its research partners created an software called DTA GView − a '
Google Maps Google Maps is a web mapping platform and consumer application offered by Google. It offers satellite imagery, aerial photography, street maps, 360° interactive panoramic views of streets (Street View), real-time traffic conditions, and rou ...
of
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...
s', in which genomes of several organisms can be pulled up on the program to immediately show a list of known genes and where they are located in the genome. According to Alicia Jackson, deputy director of DARPA's Biological Technologies Office, they have developed a "technological toolkit to transform not just hostile places here on Earth, but to go into space not just to visit, but to stay".


Paraterraforming

Also known as the "world house" concept, para-terraforming involves the construction of a habitable enclosure on a planet that encompasses most of the planet's usable area. The enclosure would consist of a transparent roof held one or more kilometers above the surface, pressurized with a breathable atmosphere, and anchored with tension towers and cables at regular intervals. The world house concept is similar to the concept of a domed habitat, but one which covers all (or most) of the planet.


Adapting humans

It has also been suggested that instead of or in addition to terraforming a hostile environment humans might adapt to these places by the use of
genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of technologies used to change the genetic makeup of cells, including ...
,
biotechnology Biotechnology is the integration of natural sciences and engineering sciences in order to achieve the application of organisms, cells, parts thereof and molecular analogues for products and services. The term ''biotechnology'' was first used ...
and cybernetic enhancements.


Issues


Ethical issues

There is a philosophical debate within
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...
and
ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...
as to whether terraforming other worlds is an
ethical Ethics or moral philosophy is a branch of philosophy that "involves systematizing, defending, and recommending concepts of right and wrong behavior".''Internet Encyclopedia of Philosophy'' The field of ethics, along with aesthetics, concerns ma ...
endeavor. From the point of view of a cosmocentric ethic, this involves balancing the need for the preservation of human life against the intrinsic value of existing planetary ecologies. Lucianne Walkowicz has even called terraforming a "planetary-scale strip mining operation". On the pro-terraforming side of the argument, there are those like Robert Zubrin, Martyn J. Fogg, Richard L. S. Taylor, and the late
Carl Sagan Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on ex ...
who believe that it is humanity's moral obligation to make other worlds suitable for human
life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energy ...
, as a continuation of the history of life-transforming the environments around it on Earth.Robert Zubrin, '' The Case for Mars: The Plan to Settle the Red Planet and Why We Must'', pp. 248–249, Simon & Schuster/Touchstone, 1996, They also point out that Earth would eventually be destroyed if nature takes its course, so that humanity faces a very long-term choice between terraforming other worlds or allowing all terrestrial life to become
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
. Terraforming totally barren planets, it is asserted, is not morally wrong as it does not affect any other life. The opposing argument posits that terraforming would be an unethical interference in
nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...
, and that given humanity's past treatment of Earth, other planets may be better off without human interference. Still others strike a middle ground, such as
Christopher McKay Dr Christopher P. McKay (born 1954) is an American planetary scientist at NASA Ames Research Center, studying planetary atmospheres, astrobiology, and terraforming. McKay majored in physics at Florida Atlantic University, where he also studied ...
, who argues that terraforming is ethically sound only once we have completely assured that an alien planet does not harbor life of its own; but that if it does, we should not try to reshape it to our own use, but we should engineer its environment to artificially nurture the alien life and help it thrive and co-evolve, or even co-exist with humans.Christopher McKay and Robert Zubrin, "Do Indigenous Martian Bacteria have Precedence over Human Exploration?", pp. 177–182, in ''On to Mars: Colonizing a New World'', Apogee Books Space Series, 2002, Even this would be seen as a type of terraforming to the strictest of ecocentrists, who would say that all life has the right, in its home biosphere, to evolve without outside interference.


Economic issues

The initial cost of such projects as planetary terraforming would be massive, and the infrastructure of such an enterprise would have to be built from scratch. Such
technology Technology is the application of knowledge to reach practical goals in a specifiable and reproducible way. The word ''technology'' may also mean the product of such an endeavor. The use of technology is widely prevalent in medicine, scien ...
has not yet been developed, let alone financially feasible at the moment. John Hickman has pointed out that almost none of the current schemes for terraforming incorporate economic strategies, and most of their models and expectations seem highly optimistic.


Political issues

National pride, rivalries between nations, and the politics of
public relations Public relations (PR) is the practice of managing and disseminating information from an individual or an organization (such as a business, government agency, or a nonprofit organization) to the public in order to influence their perception. ...
have in the past been the primary motivations for shaping space projects. It is reasonable to assume that these factors would also be present in planetary terraforming efforts.


In popular culture

Terraforming is a common concept in
science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...
, ranging from
television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertising, ...
,
movies A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmospher ...
and
novels A novel is a relatively long work of narrative fiction, typically written in prose and published as a book. The present English word for a long work of prose fiction derives from the for "new", "news", or "short story of something new", itself ...
to
video games Video games, also known as computer games, are electronic games that involves interaction with a user interface or input device such as a joystick, controller, keyboard, or motion sensing device to generate visual feedback. This feedbac ...
. A related concept from science fiction is xenoforming – a process in which
aliens Alien primarily refers to: * Alien (law), a person in a country who is not a national of that country ** Enemy alien, the above in times of war * Extraterrestrial life, life which does not originate from Earth ** Specifically, intelligent extrater ...
change the Earth or other planets to suit their own needs, already suggested in the classic ''
The War of the Worlds ''The War of the Worlds'' is a science fiction novel by English author H. G. Wells, first serialised in 1897 by ''Pearson's Magazine'' in the UK and by ''Cosmopolitan (magazine), Cosmopolitan'' magazine in the US. The novel's first appear ...
'' (1898) of H.G. Wells.


See also

* * * * * * * * * * * * * * *


Notes


References

* * * Dalrymple, G. Brent (2004). ''Ancient Earth, ancient skies: the age of Earth and its cosmic surroundings''.
Stanford University Press Stanford University Press (SUP) is the publishing house of Stanford University. It is one of the oldest academic presses in the United States and the first university press to be established on the West Coast. It was among the presses officially ...
. * Faure, Gunter & Mensing, Teresa M. (2007). ''Introduction to planetary science: the geological perspective''. Springer. . * * * * Fogg, Martyn J. (2000)
The Ethical Dimensions of Space Settlement
(PDF format). ''Space Policy'', 16, 205–211. Also presented (1999) at the 50th International Astronautical Congress,
Amsterdam Amsterdam ( , , , lit. ''The Dam on the River Amstel'') is the capital and most populous city of the Netherlands, with The Hague being the seat of government. It has a population of 907,976 within the city proper, 1,558,755 in the urban ar ...
(IAA-99-IAA.7.1.07). * Forget, François; Costard, François & Lognonné, Philippe (2007). ''Planet Mars: Story of Another World''. Springer. . * Kargel, Jeffrey Stuart (2004). ''Mars: a warmer, wetter planet''. Springer. . * * * McKay Christopher P. & Haynes, Robert H. (1997). "Implanting Life on Mars as a Long Term Goal for Mars Exploration", in ''The Case for Mars IV: Considerations for Sending Humans'', ed. Thomas R. Meyer (San Diego, California: American Astronautical Society/Univelt), Pp. 209–15. * Read, Peter L.; Lewis, Stephen R. (2004). ''The Martian climate revisited: atmosphere and environment of a desert planet''. Springer. . * Sagan, Carl & Druyan, Ann (1997). ''Pale Blue Dot: A Vision of the Human Future in Space''. Ballantine Books. . * Schubert, Gerald; Turcotte, Donald L.; Olson, Peter. (2001). ''Mantle convection in the Earth and planets''. Cambridge University Press. . * Taylor, Richard L. S. (1992). "Paraterraforming – The world house concept". '' Journal of the British Interplanetary Society'', vol. 45, no. 8, pp. 341–352. . . * Thompson, J. M. T. (2001). ''Visions of the future: astronomy and Earth science''.
Cambridge University Press Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by King Henry VIII in 1534, it is the oldest university press in the world. It is also the King's Printer. Cambridge University Pr ...
. .


External links


New Mars forum

Terraformers Society of Canada




* ttp://www.terraformers.info/ Terraformers Australia
Terraformers UK

The Terraformation of Worlds

Terraformation de Mars
* Fogg, Martyn J
The Terraforming Information Pages

BBC article on Charles Darwin's and Joseph Hooker's artificial ecosystem on Ascension Island that may be of interest to terraforming projects
*
Robotic Lunar Ecopoiesis Test Bed
Principal Investigator: Paul Todd (2004) {{Space colonization Ecosystems Open problems Planetary engineering Science fiction themes Space colonization