Natural Resources

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

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.

Mars

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.

Issues

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).

James Bell

Bibliography

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.