Emissions trading is a market-based approach to controlling pollution by providing economic incentives for achieving reductions in the emissions of pollutants. A central authority allocates or sells a limited number of permits to discharge specific quantities of a specific pollutant per time period. Polluters are required to hold permits in amount equal to their emissions. Polluters that want to increase their emissions must buy permits from others willing to sell them. Financial derivatives of permits can be traded on secondary markets. Various countries and groups of companies have adopted such trading systems, notably for mitigating climate change. In contrast to command-and-control environmental regulations such as best available technology standards and government subsidies and trade programs are a type of flexible environmental regulation that allows organizations to decide how best to meet policy targets. There are active trading programs in several air pollutants. For greenhouse gases, which cause climate change, permit units are called carbon credits.
The largest greenhouse gases trading program is the European Union Emission Trading Scheme, which trades in European Union Allowances. The United States has a national market to reduce acid rain and several regional markets in nitrogen oxides. Recent reduction in California's GHG emissions are not attributed to carbon trading but to other factors such as renewable portfolio standards and energy efficiency policies. GHG emissions increased at more than half of industrial point sources regulated by California's cap and trade program from 2013 to 2015. In theory, polluters who can reduce emissions most cheaply will do so, achieving the emission reduction at the lowest cost to society. Cap and trade is meant to provide the private sector with the flexibility required to reduce emissions while stimulating technological innovation and economic growth. In practice the theory can fall short. Environmental hotspots arise and impact areas nearest pollution sources when credits are purchased in lieu of emission reductions.
In addition to environmental justice issues cap and trade policy is not as effective as performance standards for reducing air pollutant emissions. For example, sulfur dioxide emissions and acidic sulfate deposition decreased to a larger extent more in Europe than in the United States over similar time periods with Europe employing traditional control approaches compared to the U. S.' Subsidized market approach. Pollution is a prime example of a market externality. An externality is an effect of some activity on an entity, not party to a market transaction related to that activity. Emissions trading is a market-based approach to address pollution; the overall goal of an emissions trading plan is to minimize the cost of meeting a set emissions target. In an emissions trading system, the government sets an overall limit on emissions, defines permits, or limited authorizations to emit, up to the level of the overall limit; the government may sell the permits, but in many existing schemes, it gives permits to participants equal to each participant's baseline emissions.
The baseline is determined by reference to the participant's historical emissions. To demonstrate compliance, a participant must hold permits at least equal to the quantity of pollution it emitted during the time period. If every participant complies, the total pollution emitted will be at most equal to the sum of individual limits; because permits can be bought and sold, a participant can choose either to use its permits exactly. In effect, the buyer pays a charge for polluting, while the seller gains a reward for having reduced emissions. In many schemes, organizations which do not pollute may trade permits and financial derivatives of permits. In some schemes, participants can bank allowances to use in future periods. In some schemes, a proportion of all traded permits must be retired periodically, causing a net reduction in emissions over time. Thus, environmental groups may buy and retire permits, driving up the price of the remaining permits according to the law of demand. In most schemes, permit owners can receive a tax deduction.
The government lowers the overall limit over time, with an aim towards a national emissions reduction target. According to the Environmental Defense Fund, cap-and-trade is the most environmentally and economically sensible approach to controlling greenhouse gas emissions, the primary cause of global warming, because it sets a limit on emissions, the trading encourages companies to innovate in order to emit less."International trade can offer a range of positive and negative incentives to promote international cooperation on climate change. Three issues are key to developing constructive relationships between international trade and climate agreements: how existing trade policies and rules can be modified to be more climate friendly.
In economics, a public good is a good, both non-excludable and non-rivalrous in that individuals cannot be excluded from use or could be enjoyed without paying for it, where use by one individual does not reduce availability to others or the goods can be consumed by more than one person. This is in contrast to a common good, non-excludable but is rivalrous to a certain degree. Public goods include knowledge, official statistics, national security, common language, flood control systems and street lighting. Public goods that are available everywhere are sometimes referred to as global public goods. Examples of public good knowledge is mens and youth health awareness, environmental issues, maintaining biodiversity and interpreting contemporary history with a cultural lexicon about protected cultural heritage sites and monuments and entertaining tourist attractions and universities. Many public goods may at times be subject to excessive use resulting in negative externalities affecting all users.
Public goods problems are closely related to the "free-rider" problem, in which people not paying for the good may continue to access it. Thus, the good may be overused or degraded. Public goods may become subject to restrictions on access and may be considered to be club goods. There is a good deal of debate and literature on how to measure the significance of public goods problems in an economy, to identify the best remedies. There is an important conceptual difference between the sense of "a" public good, or public "goods" in economics, the more generalized idea of "the public good", "a shorthand signal for shared benefit at a societal level". In a non-economic sense, the term is used to describe something, useful for the public such as education, although this is not a "public good" in the economic sense. However, services like education exhibit jointness of supply, i.e. the situation in which the cost of supplying a good to many users is the same, or nearly the same, as supplying it to one user.
Public goods exhibit jointness of supply, albeit with no diminishment of the benefits with increased consumption. Paul A. Samuelson is credited as the first economist to develop the theory of public goods. In his classic 1954 paper The Pure Theory of Public Expenditure, he defined a public good, or as he called it in the paper a "collective consumption good", as follows: which all enjoy in common in the sense that each individual's consumption of such a good leads to no subtractions from any other individual's consumption of that good... This is the property. A pure public good exhibits a second property called non-excludability: that is, it is impossible to exclude any individuals from consuming the good. However, many goods may satisfy the two public good conditions only to a certain extent or only some of the time; these goods are known as impure public goods. The opposite of a public good is a private good. A loaf of bread, for example, is a private good. A good, rivalrous but non-excludable is sometimes called a common-pool resource.
Such goods raise similar issues to public goods: the mirror to the public goods problem for this case is the'tragedy of the commons'. For example, it is so difficult to enforce restrictions on deep-sea fishing that the world's fish stocks can be seen as a non-excludable resource, but one, finite and diminishing. Elinor Ostrom proposed additional modifications to the classification of goods to identify fundamental differences that affect the incentives facing individuals Replacing the term "rivalry of consumption" with "subtractability of use". Conceptualizing subtractability of use and excludability to vary from low to high rather than characterizing them as either present or absent. Overtly adding a important fourth type of good—common-pool resources—that shares the attribute of subtractability with private goods and difficulty of exclusion with public goods. Forests, water systems and the global atmosphere are all common-pool resources of immense importance for the survival of humans on this earth.
Changing the name of a "club" good to a "toll" good since many goods that share these characteristics are provided by small scale public as well as private associations. The definition of non-excludability states that it is impossible to exclude individuals from consumption. Technology now allows radio or TV broadcasts to be encrypted such that persons without a special decoder are excluded from the broadcast. Many forms of information goods have characteristics of public goods. For example, a poem can be read by many people without reducing the consumption of that good by others; the information in most patents can be used by any party without reducing consumption of that good by others. Official statistics provide a clear example of information goods that are public goods, since they are created to be non-excludable. Creative works may be excludable in some circumstances, however: the individual who wrote the poem may decline to share it with others by not publishing it. Copyrights and patents both encourage the creation of such non-rival goods by providing temporary monopolies, or, in the terminology of public goods, providing a legal mechanism to enforce
The commons is the cultural and natural resources accessible to all members of a society, including natural materials such as air, a habitable earth. These resources are held in common, not owned privately. Commons can be understood as natural resources that groups of people manage for individual and collective benefit. Characteristically, this involves a variety of informal norms and values employed for a governance mechanism. Commons can be defined as a social practice of governing a resource not by state or market but by a community of users that self-governs the resource through institutions that it creates; the Digital Library of the Commons defines "commons" as "a general term for shared resources in which each stakeholder has an equal interest". The term "commons" derives from the traditional English legal term for common land, which are known as "commons", was popularised in the modern sense as a shared resource term by the ecologist Garrett Hardin in an influential 1968 article called The Tragedy of the Commons.
As Frank van Laerhoven and Elinor Ostrom have stated. The precision of this distinction is not always maintained; the use of "commons" for natural resources has its roots in European intellectual history, where it referred to shared agricultural fields, grazing lands and forests that were, over a period of several hundred years, claimed as private property for private use. In European political texts, the common wealth was the totality of the material riches of the world, such as the air, the water, the soil and the seed, all nature's bounty regarded as the inheritance of humanity as a whole, to be shared together. In this context, one may go back further, to the Roman legal category res communis, applied to things common to all to be used and enjoyed by everyone, as opposed to res publica, applied to public property managed by the government; the examples below illustrate types of environmental commons. In medieval England the common was an integral part of the manor, was thus part of the estate in land owned by the lord of the manor, but over which certain classes of manorial tenants and others held certain rights.
By extension, the term "commons" has come to be applied to other resources which a community has rights or access to. The older texts use the word "common" to denote any such right, but more modern usage is to refer to particular rights of common, to reserve the name "common" for the land over which the rights are exercised. A person who has a right in, or over, common land jointly with another or others is called a commoner. In middle Europe, commons were kept, till the present; some studies have compared the German and English dealings with the commons between late medieval times and the agrarian reforms of the 18th and 19th centuries. The UK was quite radical in doing away with and enclosing former commons, while southwestern Germany had the most advanced commons structures, were more inclined to keep them; the Lower Rhine region took an intermediate position. However, the UK and the former dominions have till today a large amount of Crown land, used for community or conservation purposes.
Based on a research project by the Environmental and Cultural Conservation in Inner Asia from 1992 to 1995, satellite images were used to compare the amount of land degradation due to livestock grazing in the regions of Mongolia and China. In Mongolia, where shepherds were permitted to move collectively between seasonal grazing pastures, degradation remained low at 9%. Comparatively and China, which mandated state-owned pastures involving immobile settlements and in some cases privatization by household, had much higher degradation, at around 75% and 33% respectively. A collaborative effort on the part of Mongolians proved much more efficient in preserving grazing land. Widespread success of the Maine lobster industry is attributed to the willingness of Maine's lobstermen to uphold and support lobster conservation rules; these rules include harbor territories not recognized by the state, informal trap limits, laws imposed by the state of Maine. The lobstermen collaborate without much government intervention to sustain their common-pool resource.
In the late 1980s, Nepal chose to decentralize government control over forests. Community forest programs work by giving local areas a financial stake in nearby woodlands, thereby increasing the incentive to protect them from overuse. Local institutions regulate harvesting and selling of timber and land, must use any profit towards community development and preservation of the forests. In twenty years, locals have noticed a visible increase in the number of trees. Community forestry may contribute to community development in rural areas – for instance school construction and drinking water channel construction, road construction. Community forestry has proven conducive to democratic practices at grass roots level. Acequia is a method of collective responsibility and management for irrigation systems in desert areas. In New Mexico, a community-run organization known as Acequia Associations
Fishing is the activity of trying to catch fish. Fish are caught in the wild. Techniques for catching fish include hand gathering, netting and trapping. “Fishing” may include catching aquatic animals other than fish, such as molluscs, cephalopods and echinoderms. The term is not applied to catching farmed fish, or to aquatic mammals, such as whales where the term whaling is more appropriate. In addition to being caught to be eaten, fish are caught as recreational pastimes. Fishing tournaments are held, caught fish are sometimes kept as preserved or living trophies; when bioblitzes occur, fish are caught and released. According to the United Nations FAO statistics, the total number of commercial fishermen and fish farmers is estimated to be 38 million. Fisheries and aquaculture provide direct and indirect employment to over 500 million people in developing countries. In 2005, the worldwide per capita consumption of fish captured from wild fisheries was 14.4 kilograms, with an additional 7.4 kilograms harvested from fish farms.
Fishing is an ancient practice that dates back to at least the beginning of the Upper Paleolithic period about 40,000 years ago. Isotopic analysis of the skeletal remains of Tianyuan man, a 40,000-year-old modern human from eastern Asia, has shown that he consumed freshwater fish. Archaeology features such as shell middens, discarded fish bones, cave paintings show that sea foods were important for survival and consumed in significant quantities. Fishing in Africa is evident early on in human history. Neanderthals were fishing by about 200,000 BC to have a source of food for their families and to trade or sell. People could have developed basketry for fish traps, spinning and early forms of knitting in order to make fishing nets to be able to catch more fish in larger quantities. During this period, most people lived a hunter-gatherer lifestyle and were, of necessity on the move. However, where there are early examples of permanent settlements such as those at Lepenski Vir, they are always associated with fishing as a major source of food.
The British dogger was an early type of sailing trawler from the 17th century, but the modern fishing trawler was developed in the 19th century, at the English fishing port of Brixham. By the early 19th century, the fishermen at Brixham needed to expand their fishing area further than before due to the ongoing depletion of stocks, occurring in the overfished waters of South Devon; the Brixham trawler that evolved there was of a sleek build and had a tall gaff rig, which gave the vessel sufficient speed to make long distance trips out to the fishing grounds in the ocean. They were sufficiently robust to be able to tow large trawls in deep water; the great trawling fleet that built up at Brixham, earned the village the title of'Mother of Deep-Sea Fisheries'. This revolutionary design made large scale trawling in the ocean possible for the first time, resulting in a massive migration of fishermen from the ports in the South of England, to villages further north, such as Scarborough, Grimsby and Yarmouth, that were points of access to the large fishing grounds in the Atlantic Ocean.
The small village of Grimsby grew to become the largest fishing port in the world by the mid 19th century. An Act of Parliament was first obtained in 1796, which authorised the construction of new quays and dredging of the Haven to make it deeper, it was only in the 1846, with the tremendous expansion in the fishing industry, that the Grimsby Dock Company was formed. The foundation stone for the Royal Dock was laid by Albert the Prince consort in 1849; the dock covered 25 acres and was formally opened by Queen Victoria in 1854 as the first modern fishing port. The elegant Brixham trawler spread across the world. By the end of the 19th century, there were over 3,000 fishing trawlers in commission in Britain, with 1,000 at Grimsby; these trawlers were sold to fishermen including from the Netherlands and Scandinavia. Twelve trawlers went on to form the nucleus of the German fishing fleet; the earliest steam powered fishing boats first appeared in the 1870s and used the trawl system of fishing as well as lines and drift nets.
These were large boats 80–90 feet in length with a beam of around 20 feet. They travelled at 9 -- 11 knots; the earliest purpose built fishing vessels were designed and made by David Allan in Leith, Scotland in March 1875, when he converted a drifter to steam power. In 1877, he built. Steam trawlers were introduced at Hull in the 1880s. In 1890 it was estimated; the steam drifter was not used in the herring fishery until 1897. The last sailing fishing trawler was built in 1925 in Grimsby. Trawler designs adapted as the way they were powered changed from sail to coal-fired steam by World War I to diesel and turbines by the end of World War II. In 1931, the first powered drum was created by Laurie Jarelainen; the drum was a circular device, set to the side of the boat and would draw in the nets. Since World War II, radio navigation aids and fish finders have been used; the first trawlers fished over the side, rather than over the stern. The first purpose built stern trawler was Fairtry built in 1953 at Scotland.
The ship was much larger than any other trawlers in operation and inaugurated the era of the'super trawler'. As the ship pulled its nets over the stern, it could lift out a much greater haul of up to 60 tons; the ship served as a basis for the expansion of'su
Grazing is a method of feeding in which a herbivore feeds on plants such as grasses, or other multicellular organisms such as algae. In agriculture, grazing is one method used whereby domestic livestock are used to convert grass and other forage into meat and other products. Many small selective herbivores follow larger grazers which skim off the highest, tough growth of grasses, exposing tender shoots. For terrestrial animals, grazing is distinguished from browsing in that grazing is eating grass or forbs, whereas browsing is eating woody twigs and leaves from trees and shrubs. Grazing differs from predation, it differs from parasitism because the two organisms live together in a constant state of physical externality. Water animals that feed by rasping algae and other micro-organisms from stones are called grazers-scrapers. Grazing is a method of feeding in which a herbivore feeds on plants such as grasses, or other multicellular organisms such as algae. Graminivory is a form of grazing involving feeding on grass.
Horses, capybara, grasshoppers and giant pandas are graminivores. Giant pandas are 99 % of their diet consisting of sub-alpine bamboo species. Rabbits are herbivores that feed by grazing on grass and leafy weeds, they graze and for about the first half-hour of a grazing period, followed by about half an hour of more selective feeding. If the environment is non-threatening, the rabbit remains outdoors for many hours, grazing at intervals, their diet contains large amounts of cellulose, hard to digest. Rabbits solve this problem by using a form of hindgut fermentation, they pass two distinct types of feces: hard droppings and soft black viscous pellets, the latter of which are known as caecotrophs and are eaten. Rabbits reingest their own droppings to extract sufficient nutrients. Capybara are herbivores that graze on grasses and aquatic plants, as well as fruit and tree bark; as with other grazers, they can be selective, feeding on the leaves of one species and disregarding other species surrounding it.
They eat a greater variety of plants during the dry season. While they eat grass during the wet season, they have to switch to more abundant reeds during the dry season; the capybara's jaw hinge is not perpendicular. Capybara are coprophagous as a means of obtaining bacterial gut flora to help digest the cellulose in the grass that forms their normal diet, to extract the maximum protein and vitamins from their food, they may regurgitate food to masticate again, similar to cud-chewing by a cow. As with other rodents, the front teeth of capybara grow continually to compensate for the constant wear from eating grasses; the hippopotamus is a large, semi-aquatic, mammal inhabiting rivers and mangrove swamps. During the day, they remain cool by staying in the mud, they emerge at dusk to graze on grasses. While hippopotamuses rest near each other in the water, grazing is a solitary activity, their incisors can be the canines up to 50 cm. Hippos rely on their broad, horny lips to grasp and pull grasses which are ground by the molars.
The hippo is considered to be a pseudoruminant. Although grazing is associated with mammals feeding on grasslands, or more livestock in a pasture, ecologists sometimes use the word in a broader sense, to include any organism that feeds on any other species without ending the life of the prey organism. Use of the term varies more than this. Malacologists sometimes apply the word to aquatic snails that feed by consuming the microscopic film of algae and detritus—a biofilm—that covers the substrate and other surfaces underwater; the use of livestock grazing can be dated back to the Civil War. During this time land ownership was not common, ranchers grazed their cattle on the surrounding federal, land. Not having a permanent home, these cowboys would graze an area down, continue on their way. More however, cattle were rotated between summer and winter ranges. Soon the public saw how profitable cattle could be, many tried to get into the cattle business. With the appearance of free, unlimited grass and feed, the land became overcrowded and the forage depleted.
Ranchers tried to put a stop to this by using barbed wire fences to barricade their land, water sources, cattle. After failed attempts, the Taylor Grazing Act was enacted in 1934; this act was put into place to help regulate the use of public land for grazing purposes and allotted ranchers certain paddocks of land. Additionally, "fees collected for grazing livestock on public lands was returned to the appropriate grazing district to be used for range improvements"; the Taylor Grazing Act helped to stabilize ranchers' operations and allow them to continue raising their livestock. In the 19th century, grazing techniques were non-existent. Pastures would be grazed for long periods of time, wi
Workers' self-management referred to as self-management, labor management and autogestión, is a form of organizational management based on self-directed work processes on the part of an organization's workforce. Self-management is a characteristic of many forms of socialism, with proposals for self-management having appeared many times throughout the history of the socialist movement, advocated variously by libertarian and market socialists and anarchists. There are many variations of self-management. In some variants, all the worker-members manage the enterprise directly through assemblies while in other forms workers exercise management functions indirectly through the election of specialist managers. Self-management may include worker supervision and oversight of an organization by elected bodies, the election of specialized managers, or self-directed management without any specialized managers as such; the goals of self-management are to improve performance by granting workers greater autonomy in their day-to-day operations, boosting morale, reducing alienation and eliminating exploitation when paired with employee ownership.
An enterprise, self-managed is referred to as a labour-managed firm. Self-management refers to control rights within a productive organization, being distinct from the questions of ownership and what economic system the organization operates under. Self-management of an organization may coincide with employee ownership of that organization, but self-management can exist in the context of organizations under public ownership and to a limited extent within private companies in the form of co-determination and worker representation on the board of directors. An economic system consisting of self-managed enterprises is sometimes referred to as a participatory economy, self-managed economy, or cooperative economy; this economic model is a major version of market socialism and decentralized planned economy, stemming from the notion that people should be able to participate in making the decisions that affect their well-being. The major proponents of self-managed market socialism in the 20th century include the economists Benjamin Ward, Jaroslav Vanek and Branko Horvat.
The Ward–Vanek model of self-management involves the diffusion of entrepreneurial roles amongst all the partners of the enterprise. Branko Horvat notes that participation is not more desirable, but more economically viable than traditional hierarchical and authoritarian management as demonstrated by econometric measurements which indicate an increase in efficiency with greater participation in decision-making. According to Horvat, these developments are moving the world toward a self-governing socialistic mode of organization. In the economic theory of self-management, workers are no longer employees but partners in the administration of their enterprise. Management theories in favor of greater self-management and self-directed activity cite the importance of autonomy for productivity in the firm and economists in favor of self-management argue that cooperatives are more efficient than centrally-managed firms because every worker receives a portion of the profit, thereby directly tying their productivity to their level of compensation.
Historical economic figures who supported cooperatives and self-management of some kind include the anarchist Pierre Joseph Proudhon, classical economist John Stuart Mill and the neoclassical economist Alfred Marshall. Contemporary proponents of self-management include the American Marxist economist Richard D. Wolff and anarchist philosopher Noam Chomsky; the theory of the labor manager firm explains the behavior and nature of self-managed organizational forms. Although self-managed firms can coincide with worker ownership, the two are distinct concepts and one need not imply the other. According to traditional neoclassical economic theory, in a competitive market economy ownership of capital assets by labor should have no significant impact on firm performance; the classical liberal philosopher John Stuart Mill believed that worker-run and owned cooperatives would displace traditional capitalist firms in the competitive market economy due to their superior efficiency and stronger incentive structure.
While both Mill and Karl Marx thought that democratic worker management would be more efficient in the long run compared with hierarchical management, Marx was not hopeful about the prospects of labor-managed and owned firms as a means to displace traditional capitalist firms in the market economy. Despite their advantages in efficiency, in Western market economies the labor-managed firm is comparatively rare. Benjamin Ward critiqued. According to Ward, the labor-managed firm strives to maximize net income for all its members as contrasted with the traditional capitalist firms' objective function of maximizing profit for external owners; the objective function of the labor managed firm creates an incentive to limit employment in order to boost the net income of the firm's existing members. Thus, an economy consisting of labor-managed firms would have a tendency to underutilize labor and tend toward high rates of unemployment. In the 19th century, the idea of a self-managed economy was first articulated by the anarchist philosopher and economist Pierre-Joseph Proudhon.
This economic model was called mutualism to highlight the mutual relationship among individuals in this system and involved cooperatives operating in a free-market economy. The classical liberal philosopher John Stuart Mill argued worker-run cooperatives would eventu
An atmosphere is a layer or a set of layers of gases surrounding a planet or other material body, held in place by the gravity of that body. An atmosphere is more to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low; the atmosphere of Earth is composed of nitrogen, argon, carbon dioxide and other gases in trace amounts. Oxygen is used by most organisms for respiration; the atmosphere helps to protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. The current composition of the Earth's atmosphere is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms; the term stellar atmosphere describes the outer region of a star and includes the portion above the opaque photosphere. Stars with sufficiently low temperatures may have outer atmospheres with compound molecules. Atmospheric pressure at a particular location is the force per unit area perpendicular to a surface determined by the weight of the vertical column of atmosphere above that location.
On Earth, units of air pressure are based on the internationally recognized standard atmosphere, defined as 101.325 kPa. It is measured with a barometer. Atmospheric pressure decreases with increasing altitude due to the diminishing mass of gas above; the height at which the pressure from an atmosphere declines by a factor of e is called the scale height and is denoted by H. For an atmosphere with a uniform temperature, the scale height is proportional to the temperature and inversely proportional to the product of the mean molecular mass of dry air and the local acceleration of gravity at that location. For such a model atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so estimation of the atmospheric pressure at any particular altitude is more complex. Surface gravity differs among the planets. For example, the large gravitational force of the giant planet Jupiter retains light gases such as hydrogen and helium that escape from objects with lower gravity.
Secondly, the distance from the Sun determines the energy available to heat atmospheric gas to the point where some fraction of its molecules' thermal motion exceed the planet's escape velocity, allowing those to escape a planet's gravitational grasp. Thus and cold Titan and Pluto are able to retain their atmospheres despite their low gravities. Since a collection of gas molecules may be moving at a wide range of velocities, there will always be some fast enough to produce a slow leakage of gas into space. Lighter molecules move faster than heavier ones with the same thermal kinetic energy, so gases of low molecular weight are lost more than those of high molecular weight, it is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, the hydrogen escaped. Earth's magnetic field helps to prevent this, as the solar wind would enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the magnetic polar regions due to auroral activity, including a net 2% of its atmospheric oxygen.
The net effect, taking the most important escape processes into account, is that an intrinsic magnetic field does not protect a planet from atmospheric escape and that for some magnetizations the presence of a magnetic field works to increase the escape rate. Other mechanisms that can cause atmosphere depletion are solar wind-induced sputtering, impact erosion and sequestration—sometimes referred to as "freezing out"—into the regolith and polar caps. Atmospheres have dramatic effects on the surfaces of rocky bodies. Objects that have no atmosphere, or that have only an exosphere, have terrain, covered in craters. Without an atmosphere, the planet has no protection from meteoroids, all of them collide with the surface as meteorites and create craters. Most meteoroids burn up as meteors before hitting a planet's surface; when meteoroids do impact, the effects are erased by the action of wind. As a result, craters are rare on objects with atmospheres. Wind erosion is a significant factor in shaping the terrain of rocky planets with atmospheres, over time can erase the effects of both craters and volcanoes.
In addition, since liquids can not exist without pressure, an atmosphere allows liquid to be present at the surface, resulting in lakes and oceans. Earth and Titan are known to have liquids at their surface and terrain on the planet suggests that Mars had liquid on its surface in the past. A planet's initial atmospheric composition is related to the chemistry and temperature of the local solar nebula during planetary formation and the subsequent escape of interior gases; the original atmospheres started with a rotating disc of gases that collapsed to form a series of spaced rings that condensed to form the planets. The planet's atmospheres were modified over time by various complex factors, resulting in quite different outcomes; the atmospheres of the planets Venus and Mars are composed of carbon dioxide, with small quantities of nitrogen, argon and traces of other gases. The composition of Earth's atmosphere is governed by the by-products of the life that it sust