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Why Go Back to the Moon?
"All civilizations become either spacefaring or extinct." -- Carl Sagan

President Bush’s 2004 proposal to return to the Moon, this time "to stay" with a lunar outpost, has stimulated vigorous debate. A Los Angeles Times editorial (Dec.10, 2006), for example, argued forcefully that robots can do anything necessary on the Moon, and that human participation is not really needed. Given the stunning performance of American robots on Mars, this point of view is worth serious discussion. Why should we send humans back to the Moon? After all, we’ve already done it, six times, in the 20th century.

Artist's concept of a small lunar outpost Image right: This is an artist's concept of a small lunar outpost. Someday, larger lunar outposts may serve as a backup for civilization in case of a global catastrophe, like an asteroid impact or a pandemic. Credit: NASA Print-resolution copy

Taking the Los Angeles Times title, "Don’t colonize the Moon," at face value, I will first point out that the Vision for Space Exploration proposes an "outpost" on the Moon. This is hardly colonization in the sense that Europeans colonized North America. Current NASA plans are in a preliminary stage, but envisage something comparable to Little America, or the Amundsen-Scott South Pole base. These terrestrial examples – operated by humans, incidentally – have proven their scientific value over and over, helping to produce valuable evidence about the ozone hole and global warming.

The Times editorial echoes identical arguments advanced in the early 1960s, that robotic missions could produce as much as manned ones. The US did in fact have a large robotic lunar program, including 3 Rangers, 5 Surveyors, 5 Lunar Orbiters, and 2 Radio Astronomy Explorers, not counting the few unsuccessful missions. So NASA did use robots in our first lunar program. But as argued at the time, human abilities on the surface later proved far superior to robotic ones.

Neil Armstrong and his colleagues demonstrated that humans on the spot provide instant interpretation of their environment, guided by color, 3D, high resolution human vision that is only now being approached by robotic systems. Even encumbered by space suits, they could instantly recognize and collect invaluable samples such as the "Genesis Rock" of Apollo 15, an anorthosite that has proven essential to understanding the geologic history of the Moon. When the Apollo 17 rover lost a fender – which might have terminated a robotic rover’s mission – astronauts Cernan and Schmitt managed a field repair and kept driving. All the Apollo astronauts emplaced complex geophysical instrument stations, most operating for years until budget cuts forced them to be turned off.

The Soviet Union carried out several brilliant robotic surface missions, starting with the very first soft landing, Luna 9. The USSR operated two robotic rovers on the Moon for months, and carried out three robotic sample return missions, both accomplishments never matched by the US or any other country. Yet no one would seriously argue that these missions produced anything close to the results of, for example, the Apollo 15 mission. The Apollo 15 astronauts Scott and Irwin returned tens of pounds of rock and soil (including the "Genesis Rock"), drove their rover miles along the front of the lunar Apennines, drilled holes for and emplaced probes for heat flow measurements, and took hundreds of high-resolution photos of their surroundings.

Returning to the 21st century: Given these splendid accomplishments by astronauts on the Moon, why bother to go back? Should we not "declare victory" and stay on (or near) Earth? Here are some reasons go back, although not necessarily to "colonize" the Moon.

First, and most fundamental: the last few decades of space exploration and astronomy have shown that the universe is violent and dangerous, at least with respect to human life. To give a pertinent example: in 1908 an object of unknown nature – probably a comet – hit Siberia with a force equivalent to a hydrogen bomb. Had this impact happened a few hours later, allowing for the Earth’s rotation, this object would have destroyed St. Petersburg and probably much else. Going back some 65 million years, it is now essentially proven that an even greater impact wiped out not only the dinosaurs but most species living on Earth at the time. The importance of catastrophic impacts has only been demonstrated in recent decades, and space exploration has played a key role.

The bleak conclusion to which these facts point is that humanity is vulnerable as long as we are confined to one planet. Obviously, we must increase our efforts to preserve this planet and its biosphere, an effort in which NASA satellites have played a vital role for many years. But uncontrollable external events may destroy our civilization, perhaps our species. We can increase our chances of long-term survival by dispersal to other sites in the solar system.

Where can we go? At the moment, human life exists only on the Earth. But with modern technology, there are several other possibilities, starting with the Moon itself. Men have lived on the Moon for as long as three days, admittedly in cramped quarters, but they found the lunar surface easy to deal with and the Moon’s gravity comfortable and helpful. (Dropped tools, for example, didn’t float away into space as they do occasionally in Earth orbit.) To be sure, it would be an enormous and probably impossible task to transform the Moon into another Earth. However, it is clear that a lunar outpost comparable to, for example, the Little America of the 1930s, is quite feasible.

But what could such an outpost accomplish? First, it could continue the exploration of the Moon, whose surface area is roughly that of North and South America combined. Six "landings" in North America would have given us only a superficial knowledge of this continent, and essentially none about its natural resources such as minerals, oil, water power, and soil. The Moon is a whole planet, so to speak, whose value is only beginning to be appreciated.

The Moon is not only an interesting object of study, but a valuable base for study of the entire Universe, by providing a site for astronomy at all wavelengths from gamma rays to extremely long radio waves. This statement would have been unquestioned 30 years ago. But the succeeding decades of spectacular discoveries by space-based instruments, such as the Hubble Space Telescope, have led many astronomers such as Nobel Laureate John Mather to argue that the Moon can be by-passed, and that instruments in deep space at relatively stable places called Lagrangian points are more effective.

A meeting was held at the Space Telescope Science Institute in Baltimore, in November 2006, on "Astrophysics Enabled by the Return to the Moon." This institute runs the Hubble Space Telescope program. However, the consensus emerging from the Baltimore meeting was that there are still valuable astronomical uses for instruments on the lunar surface. For example, low-frequency radio astronomy can only be effective from the far side of the Moon, where static from the Earth’s aurora is shielded. Another example of Moon-based astronomy can be the search for extraterrestrial intelligence (SETI), by radio telescopes that on the far side would be shielded from terrestrial interference. Small telescopes on the Moon’s solid surface could be linked to form interferometer arrays with enormous resolving power. Astronomy in a limited sense has already been done from the Moon, namely the Apollo 16 Ultraviolet telescope emplaced by Apollo astronauts and before that, the simple TV observations of Earth-based lasers by the Surveyor spacecraft. The much-feared lunar dust had no effect on these pioneering instruments.

The Moon may offer mineral resources, so to speak, of great value on Earth. Apollo 17 astronaut Harrison Schmitt, working with the Fusion Technology Institute of the University of Wisconsin, has shown that helium 3, an isotope extremely rare on Earth, exists in quantity in the lunar soil, implanted by the solar wind. If – a very big if – thermonuclear fusion for energy is produced on Earth, helium 3 would be extremely valuable for fusion reactors because it does not make the reactor radioactive. A more practicable use of helium 3, being tested at the University of Wisconsin, is the production of short-lived medical isotopes. Such isotopes must now be manufactured in cyclotrons and quickly delivered before they decay. But Dr. Schmitt suggests that small helium 3 reactors could produce such isotopes at the hospital. In any event, research on the use of helium 3 would clearly benefit if large quantities could be exported to the Earth.

Returning to the most important reason for a new lunar program, dispersal of the human species, the most promising site for such dispersal is obviously Mars, now known to have an atmosphere and water. Mars itself is obviously a fascinating object for exploration. But it may even now be marginally habitable for astronaut visits, and in the very long view, might be "terraformed," or engineered to have a more Earth-like atmosphere and climate. This was described in Kim Stanley Robinson’s trilogy, Red Mars and its successors Green and Blue Mars. A second Earth, so to speak, would greatly improve our chances of surviving cosmic catastrophes.

Where does the Moon fit into this possibility? First, it would continue to give us experience with short interplanetary trips, which is what the Apollo missions were. These would demonstrably be relatively short and safe compared to Mars voyages, but would provide invaluable test flights, so to speak. More important, shelters, vehicles, and other equipment built for the Moon could be over-designed, and with modification could be used on Mars after being demonstrated at a lunar outpost.

Where could humanity expand to beyond Mars and the Moon? At this point, still early in the history of space exploration, it is impossible to say. The Galilean satellites of Jupiter, in particular Ganymede, might be habitable, but we venture here far into the field of science fiction. However, an outpost on the Moon is clearly possible, and would provide an invaluable stepping-stone to Mars. A species living on three planets would be far more likely to have a long history than one living only on the Earth.

To put the arguments for a return to the Moon, and a lunar outpost, in the most general terms: the Moon is essentially a whole planet, one that has so far been barely touched. But this new planet is only a few days travel away and we have already camped on it. To turn our backs on the Moon would be equivalent to European exploration stopping after Columbus’s few landings, or China’s destruction of its giant ships to concentrate on domestic problems in the 15th century.
Paul D. Lowman Jr.
14 January 2008