Lunar Bases

When humans return to Earth's Moon, they will probably first live for short periods of time in lunar outposts. Eventually, they will establish lunar bases where they can live for longer periods—months or even years. These bases may result from the growth of lunar outposts, or they may be designed as lunar bases from the outset.

Any successful lunar base must accomplish a few goals. First, it must protect and satisfy the needs of those who live there. Second, it must enable the inhabitants to get some useful work done. Finally, it must minimize the cost of operating it. Sending anything from Earth to the Moon is very expensive, so a high priority for any lunar base will be to minimize the need for resupply from Earth.

An ideal place to meet all these goals might be the Aristarchus Plateau. Located at about 25° north latitude, 50° west longitude, the Aristarchus Plateau is relatively easy to spot from Earth. Aristarchus crater, at the plateau's southeast edge, is the brightest feature on the full Moon. Aristarchus Plateau is covered by fine-grained pyroclastic glass beads formed when volcanoes erupted there more than a billion years ago. This material is a good resource, and the area is very interesting to geologists.

Protection of the Inhabitants

The most critically important function of a lunar base is to protect its inhabitants. The Moon has no atmosphere, so a lunar base must be airtight and provide breathable air. Earth's atmosphere is good for more than breathing, though. It protects humans from harmful radiation from space. A lunar base must shield those inside from radiation, and pyroclastic material can do that. From radar studies, scientists have found that the pyroclastic deposits on the Aristarchus Plateau are loose and deep enough to be easily dug up and moved around. It would be relatively easy to scoop out a trench, place a habitation module in it, and cover it with several feet of pyroclastic material. That would be enough to protect those inside.

Another way to protect a lunar base from radiation is to put it underground in a lava tube. Photographs of the Aristarchus region show many interrupted channels. These may be lava tubes that have collapsed in places. The interruptions may be places where the lava tubes are still intact. Future lunar explorers might find suitably large, intact lava tube sections that could be turned into next-generation lunar bases.

Resources to Sustain the Base

Pyroclastic deposits are good for more than just radiation shielding . The Sun produces the solar wind—gases that are blown away from the Sun. Earth's atmosphere stops the solar wind before it can reach the planet's surface, but because the Moon has no atmosphere, the solar wind impacts the lunar surface directly. These gases, mostly hydrogen with some helium and other trace components, are sometimes trapped when they hit the surface of the Moon. Because the pyroclastic deposits are fine-grained, they provide a lot of surface area. It would be possible to drive off and collect the solar wind gases from this material by heating it to a few hundred degrees.

The most abundant of the gases, hydrogen, would be very valuable. If the pyroclastic material or other lunar rocks were heated to higher temperatures, the hydrogen could be combined with oxygen to form water vapor. The water vapor could be collected and condensed into liquid water.

Water is necessary to sustain life, of course, but it could also be used as part of the energy system in a lunar base. The Sun is in the Moon's sky for about two weeks, then there is a two-week-long night. During the lunar day,photovoltaic panels could convert sunlight into electricity, but storing power for two weeks would require a lot of batteries. A better method would be to use electric power during the day to break water apart into hydrogen and oxygen. During the lunar night, the hydrogen and oxygen could be recombined in a fuel cell to produce water and power.

People living at a lunar base will want to grow as much of their own food as possible. Greenhouses could be built with sufficient radiation shielding, or plants could be grown indoors with artificial lighting. Perhaps plants could be genetically engineered to withstand the intense lunar sunlight. There will be a strong economic incentive to recycle materials as efficiently and completely as possible on the Moon, and plants will play an important role. The goal will be to recycle all human wastes (solid, liquid, and gas) completely through the greenhouses, both to reduce the need for resupply from Earth and to reduce the amount of waste disposal on the Moon. People on Earth might benefit by applying the recycling techniques developed on the Moon.

Lunar base inhabitants will also experiment with other technologies that can reduce the need for bringing materials from Earth. For example, they might be able to produce building materials simply by melting lunar soils and cooling them quickly to form molded glass. Lunar surface gravity is only one-sixth that on Earth, so materials of a given strength could support much more massive structures.

Science and Exploration from Lunar Bases

One reason to build lunar bases is to study the Moon. The Aristarchus Plateau is very interesting to geologists. The plateau itself may have been raised up by the impact that formed the nearby Imbrium basin, but this is not certain. The volcanic eruptions that produced the pyroclastic material brought material to the surface from deep in the lunar interior. Scientists can learn much by studying the geology near Aristarchus.

Of course, there are many other suitable sites for lunar bases. Many other pyroclastic deposits exist in other parts of the Moon, and scientists would like to have samples from all of them. Other locations that might provide resources for lunar bases include the lunar poles. Because the Moon's polar axis is nearly perpendicular to its orbit around the Sun, sunlight never reaches the bottom of some craters near each pole. If water molecules were deposited there, for example, when a comet hit the Moon, they might remain frozen. The Lunar Prospector spacecraft had an instrument to detect hydrogen, and it did find evidence of more hydrogen near the lunar poles. The instrument could not determine whether the hydrogen was contained in water molecules, but that is the likely explanation. If abundant water is found, a lunar base at one of the poles could get its power from photovoltaic panels located on the rim of a crater at a high point that is always in sunlight, and it could get water from the permanently shadowed bottom of the same crater.

Another place that would be interesting for geologists to study is the South Pole-Aitken basin, a giant crater located (mostly) on the lunar far-side. This basin is so big that its bottom is about 8 kilometers (5 miles) lower than the average lunar surface. Scientists would like to sample rocks from that deep in the crust.

There are other reasons to establish a lunar base besides studying the Moon. The lack of an atmosphere makes the Moon a very good place to do astronomy. Earth's atmosphere distorts the light that comes through it and even prevents much light from reaching the surface at all. (That is how it protects humans from radiation.) A telescope on the Moon would produce a clear image and could gather light of any wavelength. Because the Moon turns so slowly on its axis, a telescope anywhere on the Moon could observe its target continuously for days at a time, so even a small telescope could do useful work. With no atmosphere to scatter sunlight, observing in the daytime would be possible as well. Radio astronomers on Earth are encountering increasing problems with noise, but the farside of the Moon is the only place in the solar system that is always shielded from the radio noise from Earth. Because of the Moon's lower gravity, telescopes could eventually be built far larger on the Moon than on Earth.

The Moon could also be a good platform for observing Earth and its neighborhood in the solar system. Earth is always in the sky on the lunar nearside (although Earth turns and goes through its phases as it seems to hang in one spot). Because the Moon orbits Earth, and because Earth's magnetic field is affected and distorted by the solar wind, the Moon samples different regions of Earth's magnetosphere as it circles Earth every month.

Finally, the Moon can serve as a stepping-stone on humanity's journeys beyond Earth. It took the Apollo astronauts only about three days to travel between the Moon and Earth. A trip to Mars takes at least six months oneway with today's technology. It might be wise to test the abilities of humans to live for an extended period on the Moon before trying to live on Mars. It would be possible to make an emergency return from the Moon in a few days if necessary, but that would be difficult or impossible from Mars. Also, hydrogen and oxygen make excellent rocket fuel, so if there is abundant water at the lunar poles, the Moon may turn out to be the "last chance for gas" on the way to Mars and beyond.

see also Communities in Space (volume 4); Domed Cities (volume 4); Food Production (volume 4); Governance (volume 4); Habitats (volume 3); Living on Other Worlds (volume 4); Lunar Outposts (volume 4); Moon (volume 2); Political Systems (volume 4); Power, Methods of Generating (volume 4); Scientific Research (volume 4); Settlements (volume 4); Social Ethics (volume 4); Solar Wind (volume 2).

Chris A. Peterson

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