Exploration is hard. After all, it involves being in a place where few or none have been before, whether it is the top of a mountain, the bottom of the ocean, or the surface of another world. Historically, part of the reason that exploration is so difficult is because most explorers have had to be self-sustaining; that is, most explorers have had to bring their own provisions, whether it was food or water or heat or tools, and the portage and maintenance of these provisions naturally limits the scope and pace of exploratory activities. The most successful explorers have been those who learned to use the natural resources that they encountered along the way to enable new and unanticipated discoveries and to increase their chances of successfully reaching their goals. This "living off the land" philosophy has been crucial for the exploration of Earth, and it also applies to the exploration of space.
During the latter half of the twentieth century, humans took baby steps out into the solar system. Exploratory ventures ranged from modest robotic missions designed to perform reconnaissance of planets, moons, asteroids, and comets to the bold and expensive human missions to the Moon as part of the Apollo program. These initial forays provided a sound foundation of scientific knowledge and tested many of the basic engineering principles required for human spaceflight. However, almost all of those missions were self-sustaining. For example, robotic orbiters and landers had to carry their own propellant, which, when exhausted, meant the end of those missions. The Apollo astronauts had to bring their own oxygen and water, as well as the rocket fuel for the return trip, which ultimately limited their duration on the lunar surface. If humans are to venture farther into the solar system in the twenty-first century, it will be necessary to learn how to identify and exploit the abundant natural resources available in the places they wish to explore.
The Moon provides a good example to demonstrate this point, because the lunar surface contains a number of natural resources that could substantially enhance both exploratory and commercial space activities. For example, the lunar surface consists of minerals containing iron, silicon, titanium, aluminum, oxygen, and other elements. Experiments on the Apollo samples have demonstrated that it is fairly simple to extract these elements from lunar rocks and soils. Oxygen, especially, is a critical resource that can be used for breathing as well as generating rocket fuel. Extracted metals could be used for habitat construction or tool fabrication, and because they are dense, they offer the potential for enormous savings in the mass of raw materials that would have to be sent from Earth.
The Moon is also constantly bombarded by solar wind particles that implant hydrogen and helium into the surface. When extracted, hydrogen can be used for propellants or combined with extracted oxygen to make water. Water is another critical resource for life support, radiation shielding , and self-sustaining agriculture. Extracted helium could be used for power generation on Earth or the Moon once the technology for large-scale fusion power production matures. At a more basic level, unprocessed lunar rocks and soils are a resource that can be used for solar wind radiation shielding, thermal isolation, and heat storage for habitats and other structures built on the Moon. There may be other natural resources on the Moon, such as subsurface water or ice deposited by asteroid or comet impacts, which will be discovered only through continued exploration that is enabled by the utilization of resources that are known to be there.
Asteroids and Comets
Asteroids and comets are important space exploration targets because of their scientific value as samples of the early solar system as well as the threat to Earth posed by potential impacts. In many ways asteroids and comets are likely to offer more varied and abundant natural resources than the Moon. Like the Moon, asteroids and comets are bombarded by solar wind and have silicate minerals on their surfaces, and those surface materials can be processed to yield oxygen and hydrogen and the other potential resources. However, several asteroids are known to have abundant metallic deposits on their surfaces that are likely to be rich sources of ores for construction materials and shielding. Many asteroids and most comets are also known to be rich in volatile materials such as water ice, dry ice, and hydrated minerals as well as carbon-rich organic compounds. Once extracted, these resources could be used for life support, propellant production, and construction and shielding. Perhaps most importantly, many near-Earth asteroids and some comets are easier to get to and launch from than the Moon because of their small mass and occasional close passes by Earth. Ease of accessibility is itself a natural resource and opens up the economic possibility of efficient exportation of asteroidal or cometary natural resources to Earth and other exploration targets.
Finally, Mars will be an important focus of space exploration in the twenty-first century because of its spectacular geology and meteorology and the discovery in the twentieth century that it once may have been much more Earthlike and perhaps even hospitable to life. Mars offers abundant natural resources that will almost certainly have to be tapped to enable efficient and long-term exploration so far from Earth. These resources include many materials that are extractable from the silicate-rich rocks and soils. However, Mars is also a volatile-rich planet and has an atmosphere containing carbon dioxide and other gases with resource potential. Water is known to be trapped in a small percentage of the surface soils and is hypothesized to exist either in subsurface liquid water aquifers or in water ice permafrost deposits. Self-sustaining agriculture and oxygen production are possible by extracting or accessing this water and using the abundant atmospheric carbon dioxide to fuel photosynthesis. Light elements such as hydrogen, carbon, nitrogen, and oxygen are much more abundant on Mars than on the Moon or most asteroids, and extraction of these volatiles from crustal rocks and soils could provide raw materials for the production of propellant and manufactured goods. And because of the role of water in its geologic history, Mars is likely to have rich deposits of metals, salts, and other minerals or ores. Even modest initial developments in natural resource usage on Mars, such as those planned for robotic missions, are likely to enormously increase the efficiency and capability of Mars exploration.
There are many other potential sources of natural resources in the solar system, including cosmic dust, solar wind, and the atmospheres of gas giant planets. There are also important political, ethical, technological, and economic issues regarding natural resource exploitation that need to be addressed: What are the most energy-efficient ways to generate propellants from raw materials? Who owns mining rights on Mars and the asteroids? Will extraction activities irreparably harm the environments of other worlds? Given the difficulty of balancing environmental stewardship and natural resource extraction on Earth, this issue is particularly important and will require substantial global cooperation among all of the nations involved in future space exploration.
see also Asteroid Mining (volume 4); Comet Capture (volume 4); Earth—Why Leave? (volume 4); Environmental Changes (volume 4); Living on Other Worlds (volume 4); Lunar Bases (volume 4); Lunar Outposts (volume 4); Mars (volume 2); Mars Bases (volume 4); Mars Direct (volume 4); Moon (volume 2); Resource Utilization (volume 4); Terraforming (volume 4).
Heiken, Grant H., David T. Vaniman, and Bevan M. French. Lunar Source Book. Cambridge, UK: Cambridge University Press, 1991.
Lewis, John S., Mildred S. Matthews, and Mary L. Geurrieri. Resources of Near-Earth Space. Tucson: University of Arizona Press, 1993.
Mendell, Wendell W., ed. Lunar Bases and Space Activities of the 21st Century. Houston: Lunar and Planetary Institute, 1985.
Natural resources are those elements of the environment that are considered valuable to humans. These can be raw materials, such as trees for lumber and ore for manufacturing, or things that are directly consumed, such as groundwater to drink and animals to eat. The word "natural" means that there has been no modification by humans. A "resource" is something that is necessary for growth and reproduction. Natural resources can be divided into three categories: perpetual resources, like the Sun; potentially renewable resources, like forests; and nonrenewable resources, like fossil fuels.
While a resource can be something that is necessary for an animal as well as a human, the term "natural resource" is always used in the human context. The use of this term has increased with the growing awareness of the need to manage the use of these resources to ensure their existence in the future. Many of these resources grow or form at a much slower rate than the rate at which humans are using them, and so their future is in peril. Methods to protect natural resources are complex, involving education, reduction in demand, and large-scale recycling. Global cooperation will be vital to the success of all of these tactics.
In the context of human usage, natural resources can be divided into three categories based on the possibility of resource renewal. The first category is perpetual resources. Phenomena such as solar rays, wind, tides, and flowing water will always exist within the scope of human existence. The Sun, which drives many of these phenomena, is not likely to burn out for billions of years. Harnessing solar energy or the motion of the wind or water will not decrease the quantity of these resources, which is the obvious advantage of perpetual resources.
Solar cells take the energy from the Sun's rays and turn them into electricity that can charge batteries and drive household equipment and even some specially designed automobiles. Windmills produce energy generated by the turning of their blades. But neither solar nor wind energy is commonly used because other energy sources, such as coal and gas, are less expensive in proportion to the amount of energy produced. Until a worldwide financial demand for alternative energy sources develops, technologies for exploiting these sources will lag behind common energy sources in their relative efficiency.
There are difficulties in harnessing some perpetual energy sources. One example is hydroelectric power, which is generated from flowing water that spins turbines which in turn generate electricity. The problem here is that to create enough energy for a large-scale hydroelectric plant, it is necessary to build huge dams. These dams must increase the potential energy of the water. They must also ensure that energy delivery does not stop during seasonal decreases in water flow on the rivers upon which the dams are built.
These huge dams allow sediments in the water to settle out so that ultimately, in anywhere from 40 to 300 years, the system becomes clogged. Also, the lake that is formed inundates the upstream shallow habitat on which many fishes rely, changes the downstream flow patterns, and does not allow species to travel the full length of the river, which some species need to do for breeding purposes.
With the growing realization that some resources are being used up, there has been a focus on renewable resources, the second category of natural resources. This category includes plants, animals, fertile soils, and clean air and water. These may be more accurately described as potentially renewable, because in many places they are not being actively renewed. That is because in the short term it is more economical to exhaust one area and then go to a new one instead of renewing the resource.
Harvesting trees, for example, is most economical when the entire forest is harvested, which is known as clear-cutting. That way, machines have easier access to do the cutting and transport of the logs. Unfortunately, the cleared landscape does not support the same species that were there previously. In addition, this landscape is subject to extensive soil erosion. To maintain the forest in its prior state, some trees must remain standing to conserve the soil, and efforts must be made to replant the same species that were harvested. Both cost more money and take more time than simply moving to a new area to harvest.
Another example involves drinking water. In many areas, drinking water supplies are contaminated because of poor sewage systems and runoff from human activities like farming and industry. It is proving less expensive to haul water in from other areas than to correct the cause of the problem. Therefore, this approach is becoming more common. Until an increase in consumer demand for resources that are truly being renewed alters political action and financial motivation, many potentially renewable resources will continue to be threatened.
The third and final category of natural resources is nonrenewable resources, which includes fossil fuels and minerals. These resources take extensive geological time to form, and are therefore essentially finite. Oil and natural gas are fossil fuels, which constitute an essential energy source of developed countries. They are burned to generate electricity and to power combustion engines, as in automobiles and airplanes. Minerals like iron and gold are mined from the earth as low-quality ore and then processed into pure forms that are used as building materials.
Nearly all the steps for obtaining and using nonrenewable resources are harmful to the environment. Drilling and mining to get the raw materials almost always drastically disturbs or destroys the area being explored. Processing the raw materials involves a great deal of energy and chemicals that produce toxic by-products. Finally, the use of fossil-fuel-based products like gasoline causes air and water pollution.
The conservation of natural resources involves many steps, the first of which is a global change of attitude toward conservation that places a priority on reducing consumption. The number of people and the amount of resources each person consumes must be reduced in order to lower the usage of natural resources. This will be no easy matter. Reducing the number of people having an impact would be a difficult step for areas where large families are of religious or economic importance. Also, reducing the amount each person consumes is contrary to the notion of progress in the most developed countries. Hopefully, education will help reduce the demand for nonrenewable resources and increase the use of perpetual and renewable resources before shortages dictate these changes.
see also Habitat; Habitat Loss.
Jean K. Krejca
Dunell, Lee. State of the Ark: An Atlas of Conservation in Action. London: Gaia Books, 1986.
Jeffries, Michael J. Biodiversity and Conservation. London: Routledge, 1997.
Mackenzie, Susan H. Integrated Resource Planning and Management. Washington, D.C.: Island Press, 1996.
Miller, G. Tyler, Jr. Environmental Science, 3rd ed. Belmont, CA: Wadsworth Publishing, 1991.
Warren, Andrew, and Frank Barrie Goldsmith, eds. Conservation in Practice. London: Wiley, 1974.
Natural resources, unlike man-made resources, exist independently of human labor. Natural resources can be viewed as an endowment or a gift to humankind. These resources are, however, not unlimited and must be used with care. Some natural resources are called "fund resources" because they can be exhausted through use, like the burning of fossil fuels . Other fund resources such as metals can be dissipated or wasted if they are discarded instead of being reused or recycled. Some natural resources can be used up like fund resources, but they can renew themselves if they're not completely destroyed. Examples of the latter would include the soil , forests, and fisheries.
Because of population growth and a rising standard of living, the demand for natural resources is steadily increasing. For example, the rising demand for minerals, if continued, will deplete the known and expected reserves within the coming decades.
The world's industrialized nations are consuming nonrenewable resources at an accelerating pace, with the United States ranking first on a per capita basis. With only 5% of the global population, Americans consumes 30% of the world's resources. Because of their tremendous demand for goods, Americans have also created more waste than is generated by any other country. The environment in the United States has been degraded with an ever-increasing volume and variety of contaminants. In particular, a complex of synthetic chemicals with a vast potential for harmful effects on human health has been created. The long-term effects of a low dosage of many of these chemicals in our environment will not be known for decades. The three most important causes for global environmental problems today are population growth, excessive resource consumption, and high levels of pollution . All of these threaten the natural resource base.
[Terence H. Cooper ]
Craig, J. R. Resources of the Earth. Englewood Cliffs, NJ: Prentice-Hall, 1988.
Meadows, D. H., et al. The Limits to Growth. New York: Universe Books, 1972.
Simmons, I. G. Earth, Air, and Water: Resources and Environment in the Late 20th Century. London: Edward Arnold, 1991.