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Saturday, July 2, 2022

Eco-nationalism

From Wikipedia, the free encyclopedia

Eco-nationalism (also known as ecological nationalism or green nationalism) is a synthesis of nationalism and green politics. Eco-nationalists may be from many points across the left–right political spectrum, but all are bound to the idea that the nation-state and its citizens have a special duty to protect the environment of their country.

Definitions and tenets

According to Jane Dawson, eco-nationalism is the rise of social movements that closely connect problems of environment protection with nationalist concerns. Dawson also surmised that eco-nationalism is "the synthesis of environmentalism, national identity, and the struggle for justice". Professors of history K. Sivaramakrishnan and Gunnel Cederlöf have defined eco-nationalism as, whether nativist or cosmopolitan in nature, "when the state appropriates the environment and environmental policies as forms of national pride, thereby consolidating and legitimating the nation."

One of the first instances of eco-nationalism was in the 1980s in the then Soviet Union, where citizens perceived environmental degradation as both a systemic fault of socialism and a direct result of Moscow's desire to weaken a particular nation by destroying its natural base, and exploiting its resources. Estonian, Lithuanian and Ukrainian independence movements drew great strength from environmental activism, especially from an antinuclear stance. In 1985–1991, eco-nationalism was one of the symptoms and at the same time a new impulse of the disintegration of the Soviet Union.

Eco-nationalism as defined by anthropologists often manifests in the adoption of nature as an entity outside of culture that must be protected in its pristine and untouched state whenever possible. In subaltern studies and cultural anthropology, eco-nationalism refers to the iconification of native species and landscapes in a way that appeals to a nationalist sentiment.

Eco-Ethnic-Nationalism vs Eco-Civic-Nationalism

When discussing eco-nationalism, many writers have noted it is important to understand the difference between Ethnic nationalism and Civic Nationalism. "Ethnic Nationalism" believes that the nation-state should be constructed primarily around a single ethnicity, whereas Civic Nationalism believes that the nation-state should be constructed around a diversity of people who all share common values, beliefs and culture. The former tends to be insular, isolationist, nativist, and typically right-wing while the latter is open, egalitarian, multicultural and typically more left-wing. Whether Ethno nationalist or Civic nationalist, when a nationalist group adds an environmentalist dimension to their ideology, they believe the nation-state and its citizens have a duty to protect the environment of the country.

Bioregionalism

Bioregionalism is the belief that that political, cultural, and economic systems are more environmentally sustainable and just if they are organized around naturally defined areas called bioregions. This idea that a state should conform to the natural geography of the land is compatible with the older nationalist concept of a natural border, which also believes that natural geography should determine the borders of a state. Due to the compatibility of these two ideas, Bioregionalism is often a tenet of eco-nationalist thought.

Ecotourism and Cultural Eco-Nationalism

Eco-nationalism can manifest in ecotourism, which can enrich local economies but has garnered criticism from a variety of perspectives. Artistic works that extol the virtues of a nation's natural phenomena, such as the poetry of William Wordsworth or the paintings of the Group of Seven, are another expression of eco-nationalism.

National examples

Africa

Nigeria

The flag of the Ogoni people

The struggle of the Ogoni people in Ogoniland in coastal south Nigeria against the national government has been characterised as an eco-nationalist movement by Jane Dawson. Following the discovery of oil in the region during the 1960s, the federal government altered how states in Nigeria were budgeted. Before the discovery of oil, a state's budget was based on how much it contributed to the national economy, but after the discovery of oil, the policy became that wealth must be shared out amongst all states. The result of this was that little of the newfound wealth being generated in Ogoniland was reinvested locally, and was instead redistributed to the more politically powerful states in the north of the country. The small percentage of wealth reinvested into Ogoniland was invested into building oil infrastructure, infrastructure which had dire environmental consequences on the region. As a result, Ogoni nationalism took on a distinctive environmentalist dimension in response to these issues.

Asia

India

The struggle of the practitioners of the Sarna sthal religion in India, particularly in the Jharkhand state, to receive official recognition from the state has been described by some as an "eco-nationalist" one, as the Sarna identity has been suggested to born out of a sense of nation infused with ecological thinking.

Europe

Baltic nations and Ukraine

As noted above, some of the first instances of eco-nationalism were observed in Estonia, Latvia, Lithuania and Ukraine in the 1980s. It was during this time period that nationalists in those countries discovered that the Soviet Union did not seek to block anti-government activity if it was under the banner of environmentalism. Thus nationalists in those countries threw themselves into environmental causes, particular after the Chernobyl disaster. In Estonia, eco-nationalists campaigned on the issues of oil-shale pollution, nuclear risk and mineral (phosphate) mining. In Latvia, fears about the potential damages to the natural environment by large hydro-dams on the Daugava River, as well as concerns that the symbols of the Latvian nation the Oak and Linden tree species were being destroyed. The eco-nationalism of Estonia, Latvia, Lithuania and Ukraine are described as being eco-civic-nationalist rather than eco-ethno-nationalist.

United Kingdom

Members of the Scottish Greens supporting the Yes Scotland campaign for Scottish Independence

The centre-left, civic nationalist Scottish National Party has been described in some sources as eco-nationalist; Espousing Scottish nationalism, the SNP has accused the Westminster government of being a "negligent landlord" that tosses its waste and pollution in Scotland. The SNP is noted for a longstanding willingness to work alongside environmental activists. In 2019 the SNP-led Scottish government was one of the first countries in the world to officially declare a climate emergency and followed this up with the radical Climate Change (Emissions Reduction Targets) (Scotland) Act 2019. The act was subsequently praised by the UN as "an inspiring example of the level of ambition we need globally to achieve the Paris Agreement". Following the 2021 Scottish Parliament election, the SNP and Scottish Greens entered into a ruling coalition together. Like the SNP, the Scottish Greens favour independence from the United Kingdom.

Spain

Pro-Independence Catalans during a protest in 2012. The Estelada can be seen throughout.

Republican Left of Catalonia, a Catalan nationalist party, has been described as eco-nationalist. In 2017 they passed a climate emergency declaration through the Catalan parliament that would have taken radical actions such as banning fracking, planning a closure of all nuclear facilities by 2027 and a reduction in CO2 emissions of 27% at a minimum by 2030. However, the Spanish supreme court vetoed the act after deeming it to be unconstitutional because it exceed the scope of powers granted to regional parliaments in Spain. In addition to their work in the Catalan parliament, the ERC (Esquerra Republicana de Catalunya) have been praised by the Climate Action Network for their work in the European Parliament, where between 2014 and 2019 ERC were deemed to have a pro-climate voting record even better than Spain's main green party, Greens Equo, and were ranked amongst the best performers on green issues of any party sitting in the entire European Parliament.

The left-wing Galician Nationalist Bloc has also been called eco-nationalist. The party has called for laws that would provide protection to the landscape and ecosystems while addressing issues of mobility, waste, energy, mining and water management. In 2019 the party asked for the creation of a crisis cabinet at the regional level in Spain to act on the climate emergency, as well as to tackle the threat of invasive species as a threat to water management and biodiversity.

France

In 2014, the nationalist leader of the French National Front, Marine Le Pen, launched a 'patriotic ecology' project. Termed New Ecology, the movement branded itself on a nativist form of environmentalism - encouraging locally sourced products being an example. In keeping with Le Pen's nationalist agenda, Le Pen described open borders as "anti-ecological". Conversely, Le Pen also promised to "decree an immediate moratorium on wind energy" In an article in the Huffington Post, the Danish entrepreneur Jens Martin Skibsted, reported that he once saw Marine Le Pen's father and former leader of the National Front, Jean-Marie Le Pen, "cut a water melon in two to demonstrate that green environmentalists were in fact hidden red communists."

Hungary

The Hungarian political party Our Homeland Movement has been described as chauvinistically eco-nationalist in orientation; for example, the party has called on Hungarians to show patriotism by supporting the removal of pollution from the Tisza River while simultaneously placing the blame on the pollution on Romania and Ukraine. Elements of the far-right Sixty-Four Counties Youth Movement proscribe themselves to the "Eco-Nationalist" label, with one member stating "no real nationalist is a climate denialist".

Russia

The new age religious movement Anastasianism, which stresses the people's spiritual connection to nature, has been described in academia as being "eco-nationalist" in political outlook.

Oceania

Australia and New Zealand

Patriotic pride in the country's landscape and environment is particularly visible in countries such as Australia and New Zealand, which are known for their unique animal life. Eco-nationalism is also marked by national pride in natural wonders such as the Great Barrier Reef or Mitre Peak, extensive conservation efforts towards iconic species such as the kakapo and largetooth sawfish, and the creation of National Parks in order to protect these species and areas. While beneficial for conservation efforts, eco-nationalism has been criticized as an extension of colonialist dichotomies and ontologies and rarely addresses Indigenous ecological knowledge.

The Oil Free Wellington group and its sister projects in other areas of New Zealand, a movement that campaigned against deep-sea drilling for oil off the coast of New Zealand because of the damage it was doing to the nation, has been described as another example of New Zealander Eco-Nationalism.

Satellite system (astronomy)

From Wikipedia, the free encyclopedia
 
Artist's concept of the Saturnian satellite system
A spherical yellow-brownish body (Saturn) can be seen on the left. It is viewed at an oblique angle with respect to its equatorial plane. Around Saturn there are rings and small ring moons. Further to the right large round moons are shown in order of their distance.
Saturn, its rings and major icy moons—from Mimas to Rhea.

A satellite system is a set of gravitationally bound objects in orbit around a planetary mass object (incl. sub-brown dwarfs and rogue planets) or minor planet, or its barycenter. Generally speaking, it is a set of natural satellites (moons), although such systems may also consist of bodies such as circumplanetary disks, ring systems, moonlets, minor-planet moons and artificial satellites any of which may themselves have satellite systems of their own (see Subsatellites). Some bodies also possess quasi-satellites that have orbits gravitationally influenced by their primary, but are generally not considered to be part of a satellite system. Satellite systems can have complex interactions including magnetic, tidal, atmospheric and orbital interactions such as orbital resonances and libration. Individually major satellite objects are designated in Roman numerals. Satellite systems are referred to either by the possessive adjectives of their primary (e.g. "Jovian system"), or less commonly by the name of their primary (e.g. "Jupiter system"). Where only one satellite is known, or it is a binary with a common centre of gravity, it may be referred to using the hyphenated names of the primary and major satellite (e.g. the "Earth-Moon system").

Many Solar System objects are known to possess satellite systems, though their origin is still unclear. Notable examples include the largest satellite system, the Jovian system, with 80 known moons (including the large Galilean moons) and the Saturnian System with 83 known moons (and the most visible ring system in the Solar System). Both satellite systems are large and diverse. In fact all of the giant planets of the Solar System possess large satellite systems as well as planetary rings, and it is inferred that this is a general pattern. Several objects farther from the Sun also have satellite systems consisting of multiple moons, including the complex Plutonian system where multiple objects orbit a common center of mass, as well as many asteroids and plutinos. Apart from the Earth-Moon system and Mars' system of two tiny natural satellites, the other terrestrial planets are generally not considered satellite systems, although some have been orbited by artificial satellites originating from Earth.

Little is known of satellite systems beyond the Solar System, although it is inferred that natural satellites are common. J1407b is an example of an extrasolar satellite system. It is also theorised that Rogue planets ejected from their planetary system could retain a system of satellites.

Natural formation and evolution

Satellite systems, like planetary systems, are the product of gravitational attraction, but are also sustained through fictitious forces. While the general consensus is that most planetary systems are formed from an accretionary disks, the formation of satellite systems is less clear. The origin of many moons are investigated on a case by case basis, and the larger systems are thought to have formed through a combination of one or more processes.

System stability

Gravitational accelerations at L4

The Hill sphere is the region in which an astronomical body dominates the attraction of satellites. Of the Solar System planets, Neptune and Uranus have the largest Hill spheres, due to the lessened gravitational influence of the Sun at their far orbits, however all of the giant planets have Hill spheres in the vicinity of 100 million kilometres in radius. By contrast, the Hill spheres of Mercury and Ceres, being closer to the Sun are quite small. Outside of the Hill sphere, the Sun dominates the gravitational influence, with the exception of the Lagrangian points.

Satellites are stable at the L4 and L5 Lagrangian points. These lie at the third corners of the two equilateral triangles in the plane of orbit whose common base is the line between the centers of the two masses, such that the point lies behind (L5) or ahead (L4) of the smaller mass with regard to its orbit around the larger mass. The triangular points (L4 and L5) are stable equilibria, provided that the ratio of M1/M2 is nearly 24.96. When a body at these points is perturbed, it moves away from the point, but the factor opposite of that which is increased or decreased by the perturbation (either gravity or angular momentum-induced speed) will also increase or decrease, bending the object's path into a stable, kidney-bean-shaped orbit around the point (as seen in the corotating frame of reference).

It is generally thought that natural satellites should orbit in the same direction as the planet is rotating (known as prograde orbit). As such, the terminology regular moon is used for these orbit. However a retrograde orbit (the opposite direction to the planet) is also possible, the terminology irregular moon is used to describe known exceptions to the rule, it is believed that irregular moons have been inserted into orbit through gravitational capture.

Accretion theories

Accretion disks around giant planets may occur in a similar way to the occurrence of disks around stars, out of which planets form (for example, this is one of the theories for the formations of the satellite systems of Uranus, Saturn, and Jupiter). This early cloud of gas is a type of circumplanetary disk known as a proto-satellite disk (in the case of the Earth-Moon system, the proto-lunar disk). Models of gas during the formation of planets coincide with a general rule for planet-to-satellite(s) mass ratio of 10,000:1 (a notable exception is Neptune). Accretion is also proposed by some as a theory for the origin of the Earth-Moon system, however the angular momentum of system and the Moon's smaller iron core can not easily be explained by this.

Debris disks

Another proposed mechanism for satellite system formation is accretion from debris. Scientists theorise that the Galilean moons are thought by some to be a more recent generation of moons formed from the disintegration of earlier generations of accreted moons. Ring systems are a type of circumplanetary disk that can be the result of satellites disintegrated near the Roche limit. Such disks could, over time, coalesce to form natural satellites.

Collision theories

Formation of Pluto's moons. 1: a Kuiper belt object nears Pluto; 2: the KBO impacts Pluto; 3: a dust ring forms around Pluto; 4: the debris aggregates to form Charon; 5: Pluto and Charon relax into spherical bodies.

Collision is one of the leading theories for the formation of satellite systems, particularly those of the Earth and Pluto. Objects in such a system may be part of a collisional family and this origin may be verified comparing their orbital elements and composition. Computer simulations have been used to demonstrate that giant impacts could have been the origin of the Moon. It is thought that early Earth had multiple moons resulting from the giant impact. Similar models have been used to explain the creation of the Plutonian system as well as those of other Kuiper belt objects and asteroids. This is also a prevailing theory for the origin of the moons of Mars. Both sets of findings support an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit. Collision is also used to explain peculiarities in the Uranian system. Models developed in 2018 explain the planet's unusual spin support an oblique collision with an object twice the size of Earth which likely to have re-coalesced to form the system's icy moons.

Gravitational capture theories

Animation illustrating a controversial asteroid-belt theory for the origin of the Martian satellite system

Some theories suggest that gravitational capture is the origin of Neptune's major moon Triton, the moons of Mars, and Saturn's moon Phoebe. Some scientists have put forward extended atmospheres around young planets as a mechanism for slowing the movement of a passing objects to aid in capture. The hypothesis has been put forward to explain the irregular satellite orbits of Jupiter and Saturn, for example. A tell-tale sign of capture is a retrograde orbit, which can result from an object approaching the side of the planet which it is rotating towards. Capture has even been proposed as the origin of Earth's Moon. In the case of the latter, however, virtually identical isotope ratios found in samples of the Earth and Moon cannot be explained easily by this theory.

Temporary capture

Evidence for the natural process of satellite capture has been found in direct observation of objects captured by Jupiter. Five such captures have been observed, the longest being for approximately twelve years. Based on computer modelling, the future capture of comet 111P/Helin-Roman-Crockett for 18 years is predicted to begin in 2068. However temporary captured orbits have highly irregular and unstable, the theorised processes behind stable capture may be exceptionally rare.

Controversial theories

Some controversial early theories, for example Spaceship Moon Theory and Shklovsky's "Hollow Phobos" hypothesis have suggested that moons were not formed naturally at all. These theories tend to fail Occam's razor. While artificial satellites are now a common occurrence in the Solar System, the largest, the International Space Station is 108.5 metres at its widest, is tiny compared to the several kilometres of the smallest natural satellites.

Notable satellite systems

The Pluto-Charon system (with orbital paths illustrated): The binaries Pluto and Charon orbited by Nix, Hydra, Kerberos, and Styx, taken by the Hubble Space Telescope in July 2012
 
Animation of radar images of near-Earth asteroid (136617) 1994 CC and satellite system

Known satellite systems of the Solar System consisting of multiple objects or around planetary mass objects, in order of perihelion:

Planetary Mass

Object Class Perihelion (AU) Natural satellites Artificial satellites Ring/s groups Note
Earth Planet 0.9832687 1 2,465*
See List of Earth observation satellites, List of satellites in geosynchronous orbit, List of space stations
The Moon Natural satellite 1.0102
10*
See Lunar Reconnaissance Orbiter, Lunar Orbiter program
Mars Planet 1.3814 2 11*
*6 are derelict (see List of Mars orbiters)
1 Ceres Dwarf planet 2.5577
1*
*Dawn
Jupiter Planet 4.95029 80 1 4 With ring system and four large Galilean moons. Juno since 2017. See also Moons of Jupiter and Rings of Jupiter
Saturn Planet 9.024 83
7
Uranus Planet 20.11 27
13 With ring system. See also Moons of Uranus
134340 Pluto-Charon Dwarf planet (binary) 29.658 5

See also Moons of Pluto
Neptune Planet 29.81 14
5 With ring system. See also Moons of Neptune
136108 Haumea Dwarf planet 34.952 2
1 See also Moons of Haumea, ring system discovered 2017
136199 Eris Dwarf planet (binary) 37.911 1

Binary: Dysnomia
136472 Makemake Dwarf planet 38.590 1

S/2015 (136472) 1

Small Solar System body

Object Class Perihelion (AU) Natural satellites Artificial satellites Ring/s groups Note
66391 Moshup Mercury-crosser asteroid 0.20009 1

Binary system
(66063) 1998 RO1 Aten asteroid 0.27733 1

Binary system
(136617) 1994 CC near-Earth asteroid 0.95490 2

Trinary system
(153591) 2001 SN263 near-Earth asteroid 1.03628119 2

Trinary system
(285263) 1998 QE2 near-Earth asteroid 1.0376 1

Binary system
67P/Churyumov–Gerasimenko Comet 1.2432
1*
*Rosetta, since August 2014
2577 Litva Mars-crosser 1.6423 2

Binary system
3749 Balam Main-belt Asteroid 1.9916 2

Binary system
41 Daphne Main-belt Asteroid 2.014 1

Binary system
216 Kleopatra Main-belt Asteroid 2.089 2


93 Minerva Main-belt Asteroid 2.3711 2


45 Eugenia Main-belt Asteroid 2.497 2


130 Elektra Main-belt Asteroid 2.47815 2


22 Kalliope Main-belt Asteroid 2.6139 1

Binary: Linus
90 Antiope Main-belt Asteroid 2.6606 1

Binary: S/2000 (90) 1
87 Sylvia Main-belt Asteroid 3.213 2


107 Camilla Cybele asteroid 3.25843 1

Binary: S/2001 (107) 1
617 Patroclus Jupiter Trojan 4.4947726 1

Binary: Menoetius
2060 Chiron Centaur 8.4181

2
10199 Chariklo Centaur 13.066

2 First minor planet known to possess a ring system. see Rings of Chariklo
47171 Lempo Trans-Neptunian object 30.555 2

Trinary/Binary with companion
90482 Orcus Kuiper belt object 30.866 1

Binary: Vanth
225088 Gonggong Trans-Neptunian object 33.050 1

BinaryL Xiangliu
120347 Salacia Kuiper belt object 37.296 1

Binary: Actaea
(48639) 1995 TL8 Kuiper belt object 40.085 1

Binary: S/2002 (48639) 1
1998 WW31 Kuiper belt object 40.847 1

Binary: S/2000 (1998 WW31) 1
50000 Quaoar Kuiper belt object 41.868 1

Binary: Weywot

Features and interactions

Natural satellite systems, particularly those involving multiple planetary mass objects can have complex interactions which can have effects on multiple bodies or across the wider system.

Ring systems

Model for formation of Jupiter's rings

Ring systems are collections of dust, moonlets, or other small objects. The most notable examples are those around Saturn, but the other three gas giants (Jupiter, Uranus and Neptune) also have ring systems. Studies of exoplanets indicate that they may be common around giant planets. The 90 million km (0.6 AU) circumplanetary ring system discovered around J1407b has been described as "Saturn on steroids" or “Super Saturn” Luminosity studies suggest that an even larger disk exists in the PDS 110 system.

Other objects have also been found to possess rings. Haumea was the first dwarf planet and Trans-Neptunian object found to possess a ring system. Centaur 10199 Chariklo, with a diameter of about 250 kilometres (160 mi), is the smallest object with rings ever discovered consisting of two narrow and dense bands, 6–7 km (4 mi) and 2–4 km (2 mi) wide, separated by a gap of 9 kilometres (6 mi). The Saturnian moon Rhea may have a tenuous ring system consisting of three narrow, relatively dense bands within a particulate disk, the first predicted around a moon.

Most rings were thought to be unstable and to dissipate over the course of tens or hundreds of millions of years. Studies of Saturn's rings however indicate that they may date to the early days of the Solar System. Current theories suggest that some ring systems may form in repeating cycles, accreting into natural satellites that break up as soon as they reach the Roche limit. This theory has been used to explain the longevity of Saturn's rings as well the moons of Mars.

Gravitational interactions

Orbital configurations

The Laplace resonance exhibited by three of the Galilean moons. The ratios in the figure are of orbital periods. Conjunctions are highlighted by brief color changes.
 
Rotating-frame depiction of the horseshoe exchange orbits of Janus and Epimetheus

Cassini's laws describe the motion of satellites within a system with their precessions defined by the Laplace plane. Most satellite systems are found orbiting the ecliptic plane of the primary. An exception is Earth's moon, which orbits in to the planet's equatorial plane.

When orbiting bodies exert a regular, periodic gravitational influence on each other is known as orbital resonance. Orbital resonances are present in several satellite systems:

Other possible orbital interactions include libration and co-orbital configuration. The Saturnian moons Janus and Epimetheus share their orbits, the difference in semi-major axes being less than either's mean diameter. Libration is a perceived oscillating motion of orbiting bodies relative to each other. The Earth-moon satellite system is known to produce this effect.

Several systems are known to orbit a common centre of mass and are known as binary companions. The most notable system is the Plutonian system, which is also dwarf planet binary. Several minor planets also share this configuration, including "true binaries" with near equal mass, such as 90 Antiope and (66063) 1998 RO1. Some orbital interactions and binary configurations have been found to cause smaller moons to take non-spherical forms and "tumble" chaotically rather than rotate, as in the case of Nix, Hydra (moons of Pluto) and Hyperion (moon of Saturn).

Tidal interaction

Diagram of the Earth–Moon system showing how the tidal bulge is pushed ahead by Earth's rotation. This offset bulge exerts a net torque on the Moon, boosting it while slowing Earth's rotation.

Tidal energy including tidal acceleration can have effects on both the primary and satellites. The Moon's tidal forces deform the Earth and hydrosphere, similarly heat generated from tidal friction on the moons of other planets is found to be responsible for their geologically active features. Another extreme example of physical deformity is the massive equatorial ridge of the near-Earth asteroid 66391 Moshup created by the tidal forces of its moon, such deformities may be common among near-Earth asteroids.

Tidal interactions also cause stable orbits to change over time. For instance, Triton's orbit around Neptune is decaying and 3.6 billion years from now, it is predicted that this will cause Triton to pass within Neptune's Roche limit resulting in either a collision with Neptune's atmosphere or the breakup of Triton, forming a large ring similar to that found around Saturn. A similar process is drawing Phobos closer to Mars, and it is predicted that in 50 million years it will either collide with the planet or break up into a planetary ring. Tidal acceleration, on the other hand, gradually moves the Moon away from Earth, such that it may eventually be released from its gravitational bounding and exit the system.

Perturbation and instability

While tidal forces from the primary are common on satellites, most satellite systems remain stable. Perturbation between satellites can occur, particularly in the early formation, as the gravity of satellites affect each other, and can result in ejection from the system or collisions between satellites or with the primary. Simulations show that such interactions cause the orbits of the inner moons of the Uranus system to be chaotic and possibly unstable. Some of Io's active can be explained by perturbation from Europa's gravity as their orbits resonate. Perturbation has been suggested as a reason that Neptune does not follow the 10,000:1 ratio of mass between the parent planet and collective moons as seen in all other known giant planets. One theory of the Earth-Moon system suggest that a second companion which formed at the same time as the Moon, was perturbed by the Moon early in the system's history, causing it to impact with the Moon.

Atmospheric and magnetic interaction

Gas toruses in the Jovian system generated by Io (green) and Europa (blue)

Some satellite systems have been known to have gas interactions between objects. Notable examples include the Jupiter, Saturn and Pluto systems. The Io plasma torus is a transfer of oxygen and sulfur from the tenuous atmosphere of Jupiter's volcanic moon, Io and other objects including Jupiter and Europa. A torus of oxygen and hydrogen produced by Saturn's moon, Enceladus forms part of the E ring around Saturn. Nitrogen gas transfer between Pluto and Charon has also been modelled and is expected to be observable by the New Horizons space probe. Similar tori produced by Saturn's moon Titan (nitrogen) and Neptune's moon Triton (hydrogen) is predicted.

Image of Jupiter's northern aurorae, showing the main auroral oval, the polar emissions, and the spots generated by the interaction with Jupiter's natural satellites

Complex magnetic interactions have been observed in satellite systems. Most notably, the interaction of Jupiter's strong magnetic field with those of Ganymede and Io. Observations suggest that such interactions can cause the stripping of atmospheres from moons and the generation of spectacular auroras.

History

An illustration from al-Biruni's astronomical works, explains the different phases of the moon, with respect to the position of the sun.

The notion of satellite systems pre-dates history. The Moon was known by the earliest humans. The earliest models of astronomy were based around celestial bodies (or a "celestial sphere") orbiting the Earth. This idea was known as geocentrism (where the Earth is the centre of the universe). However the geocentric model did not generally accommodate the possibility of celestial objects orbiting other observed planets, such as Venus or Mars.

Seleucus of Seleucia (b. 190 BCE) made observations which may have included the phenomenon of tides, which he supposedly theorized to be caused by the attraction to the Moon and by the revolution of the Earth around an Earth-Moon 'center of mass'.

As heliocentrism (the doctrine that the Sun is the centre of the universe) began to gain in popularity in the 16th century, the focus shifted to planets and the idea of systems of planetary satellites fell out of general favour. Nevertheless, in some of these models, the Sun and Moon would have been satellites of the Earth.

Nicholas Copernicus published a model in which the Moon orbited around the Earth in the Dē revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), in the year of his death, 1543.

It was not until the discovery of the Galilean moons in either 1609 or 1610 by Galileo, that the first definitive proof was found for celestial bodies orbiting planets.

The first suggestion of a ring system was in 1655, when Christiaan Huygens thought that Saturn was surrounded by rings.

The first probe to explore a satellite system other than Earth was Mariner 7 in 1969, which observed Phobos. The twin probes Voyager 1 and Voyager 2 were the first to explore the Jovian system in 1979.

Zones and habitability

Artist's impression of a moon with surface water oceans orbiting within the circumstellar habitable zone

Based on tidal heating models, scientists have defined zones in satellite systems similarly to those of planetary systems. One such zone is the circumplanetary habitable zone (or "habitable edge"). According to this theory, moons closer to their planet than the habitable edge cannot support liquid water at their surface. When effects of eclipses as well as constraints from a satellite's orbital stability are included into this concept, one finds that — depending on a moon's orbital eccentricity — there is a minimum mass of roughly 0.2 solar masses for stars to host habitable moons within the stellar HZ.

The magnetic environment of exomoons, which is critically triggered by the intrinsic magnetic field of the host planet, has been identified as another effect on exomoon habitability. Most notably, it was found that moons at distances between about 5 and 20 planetary radii from a giant planet can be habitable from an illumination and tidal heating point of view, but still the planetary magnetosphere would critically influence their habitability.

Atmospheric chemistry

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Atmospheric_chemistry

Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary approach of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and volcanology and other disciplines. Research is increasingly connected with other areas of study such as climatology.

The composition and chemistry of the Earth's atmosphere is of importance for several reasons, but primarily because of the interactions between the atmosphere and living organisms. The composition of the Earth's atmosphere changes as result of natural processes such as volcano emissions, lightning and bombardment by solar particles from the corona. It has also been changed by human activity and some of these changes are harmful to human health, crops and ecosystems. Examples of problems which have been addressed by atmospheric chemistry include acid rain, ozone depletion, photochemical smog, greenhouse gases and global warming. Atmospheric chemists seek to understand the causes of these problems, and by obtaining a theoretical understanding of them, allow possible solutions to be tested and the effects of changes in government policy evaluated.

Atmospheric composition

Visualisation of composition by volume of Earth's atmosphere. Water vapour is not included as it is highly variable. Each tiny cube (such as the one representing krypton) has one millionth of the volume of the entire block. Data is from NASA Langley.
 
The composition of common nitrogen oxides in dry air vs. temperature
 
Chemical composition of atmosphere according to altitude. Axis: Altitude (km), Content of volume (%).
 
Average composition of dry atmosphere (mole fractions)
Gas per NASA
Dry clean air near sea level
(standard ISO 2533 - 1975)
Nitrogen, N2 78.084% 78.084%
Oxygen, O2 20.946% 20.946%
Minor constituents (mole fractions in ppm)
Argon, Ar 9340 9340
Carbon dioxide*[a], CO2 400 314[b]
Neon, Ne 18.18 18.18
Helium, He 5.24 5.24
Methane, CH4 1.7 2.0
Krypton, Kr 1.14 1.14
Hydrogen, H2 0.55 0.5
Nitrous oxide, N2O 0.5 0.5
Xenon, Xe 0.09 0.087
Nitrogen dioxide, NO2 0.02 up to 0.02
Ozone*, O3, in summer
up to 0.07
Ozone*, O3, in winter
up to 0.02
Sulphur dioxide*, SO2
up to 1
Iodine*, I2
0.01
Water vapour* Highly variable (about 0–3%);
typically makes up about 1%
Notes
The mean molecular mass of dry air is 28.97 g/mol. *The content of the gas may undergo significant variations from time to time or from place to place. The concentration of CO2 and CH4 vary by season and location. CO2 here is from 1975, but has been increasing by about 2–3 ppm annually (see Carbon dioxide in Earth's atmosphere).

Trace gas composition

Besides the more major components listed above, Earth's atmosphere also has many trace gas species that vary significantly depending on nearby sources and sinks. These trace gases can include compounds such as CFCs/HCFCs which are particularly damaging to the ozone layer, and H
2
S
which has a characteristic foul odor of rotten eggs and can be smelt in concentrations as low as 0.47 ppb. Some approximate amounts near the surface of some additional gases are listed below. In addition to gases, the atmosphere contains particulates as aerosol, which includes for example droplets, ice crystals, bacteria, and dust.

Composition (ppt by volume unless otherwise stated)
Gas Clean continental, Seinfeld & Pandis (2016) Simpson et al. (2010)[4]
Carbon monoxide, CO 40-200 ppb  97 ppb
Nitric oxide, NO
16
Ethane, C2H6
781
Propane, C3H8
200
Isoprene, C5H8
311
Benzene, C6H6
11
Methanol, CH3OH
1967
Ethanol, C2H5OH
75
Trichlorofluoromethane, CCl3F 237 252.7
Dichlorodifluoromethane, CCl2F2 530 532.3
Chloromethane, CH3Cl
503
Bromomethane, CH3Br 9–10 7.7
Iodomethane, CH3I
0.36
Carbonyl sulfide, OCS 510 413
Sulfur dioxide, SO2 70–200 102
Hydrogen sulfide, H2S 15–340 
Carbon disulfide, CS2 15–45 
Formaldehyde, H2CO 9.1 ppb 
Acetylene, C2H2 8.6 ppb 
Ethene, C2H4 11.2 ppb  20
Sulfur hexafluoride, SF6 7.3 
Carbon tetrafluoride, CF4 79 
Total gaseous mercury, Hg 0.209 

History

Schematic of chemical and transport processes related to atmospheric composition

The ancient Greeks regarded air as one of the four elements. The first scientific studies of atmospheric composition began in the 18th century, as chemists such as Joseph Priestley, Antoine Lavoisier and Henry Cavendish made the first measurements of the composition of the atmosphere.

In the late 19th and early 20th centuries interest shifted towards trace constituents with very small concentrations. One particularly important discovery for atmospheric chemistry was the discovery of ozone by Christian Friedrich Schönbein in 1840.

In the 20th century atmospheric science moved on from studying the composition of air to a consideration of how the concentrations of trace gases in the atmosphere have changed over time and the chemical processes which create and destroy compounds in the air. Two particularly important examples of this were the explanation by Sydney Chapman and Gordon Dobson of how the ozone layer is created and maintained, and the explanation of photochemical smog by Arie Jan Haagen-Smit. Further studies on ozone issues led to the 1995 Nobel Prize in Chemistry award shared between Paul Crutzen, Mario Molina and Frank Sherwood Rowland.

In the 21st century the focus is now shifting again. Atmospheric chemistry is increasingly studied as one part of the Earth system. Instead of concentrating on atmospheric chemistry in isolation the focus is now on seeing it as one part of a single system with the rest of the atmosphere, biosphere and geosphere. An especially important driver for this is the links between chemistry and climate such as the effects of changing climate on the recovery of the ozone hole and vice versa but also interaction of the composition of the atmosphere with the oceans and terrestrial ecosystems.

Carbon dioxide in Earth's atmosphere if half of anthropogenic CO2 emissions are not absorbed
(NASA simulation; 9 November 2015)
 
Nitrogen dioxide 2014 - global air quality levels

Methodology

Observations, lab measurements, and modeling are the three central elements in atmospheric chemistry. Progress in atmospheric chemistry is often driven by the interactions between these components and they form an integrated whole. For example, observations may tell us that more of a chemical compound exists than previously thought possible. This will stimulate new modelling and laboratory studies which will increase our scientific understanding to a point where the observations can be explained.

Observation

Observations of atmospheric chemistry are essential to our understanding. Routine observations of chemical composition tell us about changes in atmospheric composition over time. One important example of this is the Keeling Curve - a series of measurements from 1958 to today which show a steady rise in of the concentration of carbon dioxide (see also ongoing measurements of atmospheric CO2). Observations of atmospheric chemistry are made in observatories such as that on Mauna Loa and on mobile platforms such as aircraft (e.g. the UK's Facility for Airborne Atmospheric Measurements), ships and balloons. Observations of atmospheric composition are increasingly made by satellites with important instruments such as GOME and MOPITT giving a global picture of air pollution and chemistry. Surface observations have the advantage that they provide long term records at high time resolution but are limited in the vertical and horizontal space they provide observations from. Some surface based instruments e.g. LIDAR can provide concentration profiles of chemical compounds and aerosol but are still restricted in the horizontal region they can cover. Many observations are available on line in Atmospheric Chemistry Observational Databases.

Laboratory studies

Measurements made in the laboratory are essential to our understanding of the sources and sinks of pollutants and naturally occurring compounds. These experiments are performed in controlled environments that allow for the individual evaluation of specific chemical reactions or the assessment of properties of a particular atmospheric constituent. Types of analysis that are of interest includes both those on gas-phase reactions, as well as heterogeneous reactions that are relevant to the formation and growth of aerosols. Also of high importance is the study of atmospheric photochemistry which quantifies how the rate in which molecules are split apart by sunlight and what resulting products are. In addition, thermodynamic data such as Henry's law coefficients can also be obtained.

Modeling

In order to synthesise and test theoretical understanding of atmospheric chemistry, computer models (such as chemical transport models) are used. Numerical models solve the differential equations governing the concentrations of chemicals in the atmosphere. They can be very simple or very complicated. One common trade off in numerical models is between the number of chemical compounds and chemical reactions modeled versus the representation of transport and mixing in the atmosphere. For example, a box model might include hundreds or even thousands of chemical reactions but will only have a very crude representation of mixing in the atmosphere. In contrast, 3D models represent many of the physical processes of the atmosphere but due to constraints on computer resources will have far fewer chemical reactions and compounds. Models can be used to interpret observations, test understanding of chemical reactions and predict future concentrations of chemical compounds in the atmosphere. One important current trend is for atmospheric chemistry modules to become one part of earth system models in which the links between climate, atmospheric composition and the biosphere can be studied.

Some models are constructed by automatic code generators (e.g. Autochem or Kinetic PreProcessor). In this approach a set of constituents are chosen and the automatic code generator will then select the reactions involving those constituents from a set of reaction databases. Once the reactions have been chosen the ordinary differential equations that describe their time evolution can be automatically constructed.

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