To those who grew up in the long shadow of the Apollo program, the moon was a fixed goal in space. The triumphant Apollo 11 landing on July 20, 1969, set the stage for Wernher von Braun’s grand vision of the human conquest of space. Next would come a permanent moon base and a space station that together would serve as the jumping-off point to Mars. Three and a half years later, that dream faded as Eugene Cernan and Harrison Schmitt climbed into a frail-looking, foil-wrapped lunar module and blasted off the moon’s surface. No human has set foot there since. The Saturn V rocket became a museum piece, and NASA bet its money instead on a fleet of space shuttles circling in low Earth orbit.
"Had we pressed on with the Saturn V, we could have had a lunar base by 1975," says Paul Lowman, a geophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Public apathy toward the current manned space program, a $100 billion International Space Station that is dismissed by most of the scientific community, and the recent Columbia disaster seem to have just about killed the old spirit of exploration. Although a new rallying cry is building for going straight to Mars, many old-time space enthusiasts insist we should start by picking up where we left off: Go back to the moon, this time to stay.
"The difficulties of a manned Mars program are staggering. When you go to the moon, you are making an interplanetary trip. It’s a short one, but you are rehearsing cheaply and relatively safely for longer interplanetary trips," Lowman says. This thinking fits with NASA’s long-held philosophy of taking incremental steps. The Space Exploration Initiative, a 30-year NASA road map presented by President Bush in 1989, called for the creation of a moon base before setting off to the Red Planet. The Aurora Programme, a strategic plan endorsed by the European Union Council of Research two years ago, similarly envisions a return to the moon as a prelude to Mars.
As a bonus, a moon base would be an ideal site for cutting-edge science. "We would use the moon as a platform for astronomy and to study the space environment," says Wendell Mendell, manager of NASA’s Office for Human Exploration Science in Houston. The moon has no wind, clouds, light pollution, or atmospheric distortion. Seismic activity is insignificant, and the rotation rate of the moon is 1/500 that of the orbital
period of the Hubble Space Telescope. A lunar telescope could conduct unbroken observations for 14 days at a time.
NASA has been enticing scientists with talk about manned observatories on the moon for nearly 40 years. "There were many of us who were willing to go on a one-way trip to set up these stations," says astronomer William Tifft at the University of Arizona, who was a NASA astronaut finalist in 1965. Today 44-year-old John Grunsfeld is the only active professional astronomer-astronaut in the corps. He has clocked more than 45 days in space on four shuttle flights, three of them focused on astronomy. He hopes science on the moon will come next, following the model of research in Antarctica: "The National Science Foundation would have never established a base at the South Pole just to support astronomy. But once the base was established, astronomy followed, and some of the most exciting results have come from there."
By coincidence, the south polar region of the moon-a 1,500-mile-wide depression known as the Aitken Basin-is where the first permanent lunar base is most likely to be built. Mendell describes a concept that echoes NASA’s plans from the 1960s: "The initial missions will almost certainly be multiple and Apollo-like but longer, perhaps two weeks, with four people on the surface. These missions will in a short time lead to a longer-term mission at the lunar south pole. If we can get the thing rolling, do the technology right, manage the cost, and convince the nation that it’s the right thing to do, we could be landing on the moon again in 10 years."
A prime attraction of the moon’s south pole is its "mountain of eternal light," a peak that receives sunlight at least 70 percent of the time. Solar panels there could generate near-constant power for people and instruments. Equally enticing, some permanently shadowed craters near the lunar south pole seem to contain ice, which could provide water and air for the base. The south pole also intrigues planetary scientists who believe some of the rocks there may have originated deep within the lunar interior. A study of this region might reveal the moon’s true composition, and hence its origin. "One of the original rationales for going to the moon was to find out how it formed, but we still don’t know. If we could put people down again, we would have a definitive answer within 15 years," Lowman says. The prevailing theory holds that the moon was created from debris knocked loose when a Mars-size body collided with the embryonic Earth. This collision may also have triggered Earth’s plate tectonics, key to the recycling of carbon dioxide through our ecosystem.
If a permanent base is established, Lowman envisions constructing at least four optical astronomical sites-two 180 degrees apart on the moon’s equator and one each at the lunar north and south poles. Another possibility would be to deploy an optical interferometer, a device that combines the light from multiple telescopes to create a single superhigh resolution instrument. Both NASA and the European Space Agency (ESA) are contemplating interferometry missions in space, but servicing the instruments and maintaining the precise alignment of separate telescopes in the void is difficult. Near a moon base, neither access nor stability would be a problem.
Building a large-scale interferometer would signal a revolution in optical astronomy. "It would have several hundred times the resolution of the Hubble," says Mike Shao, an optical engineer and physicist at the Jet Propulsion Laboratory (JPL). "You would see what you could see with the James Webb Space Telescope, but with angular resolution that is a hundred times higher." On the moon, interferometry could also be applied to the submillimeter spectrum, halfway between radio and infrared wavelengths. Submillimeter emissions are typically produced by carbon and water molecules in distant galaxies and star-forming regions. Detecting these waves is difficult at best on Earth, due to interference from water in the atmosphere. The moon would offer astronomers a high-resolution window onto the submillimeter universe. "If anyone would offer us the opportunity to put a submillimeter array on the moon, we would grab it," says Tom Phillips, the director of the Caltech Submillimeter Observatory on Mauna Kea in Hawaii. "Submillimeter has the ability to look at the cool, distant universe in a way that no other frequency can."
The lunar surface may also be the best spot in the solar system to tune in to very low frequency (VLF) radio waves. For all practical purposes, ground-based VLF astronomy does not exist. That is because almost all VLF waves are blocked by Earth’s ionosphere, and our planet itself is a natural source of emissions. Dayton Jones and Thomas Kuiper, radio astronomers at JPL, have sketched a plan for deploying a rover to build a VLF radio telescope-essentially a huge network of wires acting as radio-wave receivers-in a crater on the lunar farside, where the moon’s bulk blots out Earth’s radio noise. VLF waves might reveal "fossil" galaxies that were once highly active; they could also be used to map ancient supernova remnants in the Milky Way.
So far, neither NASA nor the ESA has finalized a specific plan for a moon base. Engineers on both sides of the Atlantic say that technology is not a stumbling block, however. The ESA’s Aurora Programme proposes using an enhanced Ariane 5 launcher to ferry a crew to lunar orbit, in the style of the old Saturn V; Mendell says Boeing’s Delta IV launcher could also be enhanced to carry humans to the moon. Further ahead, NASA’s Orbital Space Plane, planned for a 2012 launch, might be able to travel to lunar orbit, depending on the final design. Once there, the plane could dock with a lunar lander placed in orbit before it arrived. Gary Martin, named space architect at NASA in 2002, says that a manned Mars mission would most likely use a similar set of steps.
The monumental hurdle for NASA will be mustering funding and political support to revisit a world it explored more than a generation ago. Last year, Representative Nick Lampson, a Texas Democrat whose home district includes the Johnson Space Center, introduced a bill mandating manned missions to the moon within 15 years. It never even came to a vote.
In classic NASA style, Martin hedges his bets when discussing the agency’s human-exploration plans: "Our strategy is to build a very sustainable program where people are routinely going into deep space. If you rush it, we will go there for one time and we’ll have another hiatus for 30 years."