James Burke noted that the orbiting International Space Station is closer to Earth than Penn State is to Pittsburgh. By contrast, the Moon is around 240,000 miles out into space. A retired aeronautical engineer with Caltech's Jet Propulsion Lab, Burke told the audience at the fifth of the 2003 Frontiers of Science lectures: The Moon is a natural space station, already in Earth orbit and ready to inhabit.
I'm an advocate for lunar living—for cities on the Moon, ultimately, he said. I'm not talking about just camping there and exploring. I'm talking about people residing on the Moon comfortably and productively for long periods. Burke—a faculty member of the International Space University in Strasbourg, France, and a trustee of the Space Studies Institute at Princeton University—pointed at two potential achievements on the Moon that would advance our civilization greatly. From an intellectual perspective, we could acquire knowledge that's accessible nowhere else. From a practical standpoint, he said, we could recover enough energy that we would no longer need to rely on polluting, non-renewable fossil fuels on Earth.
Burke gave a brief rundown of Earth's satellite and probable child: The Moon was created when an object the size of Mars slammed into the Earth and blasted away a great chunk of the planet. That cataclysmic event happened 4.35 billion years ago, during the formation of the solar system and about 650 million years after the Sun had come into being. Early on, the Moon had an ocean of magma; over millennia, its internal heat engine cooled, and now it is frigid and inert. At one time the Moon was much closer to us than it is today; over time, it has drifted farther into space, and at some point it will escape Earth's gravity altogether. (Growth rings in fossilized coral imply much higher tides in Earth's past, evidence of a nearer mass—the Moon—exerting its own gravity on its planetary parent.) The Moon has a dense, rocky mantle; a crust that is less dense; and perhaps a compact metallic core.
Even though the late 20th century saw a complete revolution in our understanding of the Moon, Burke said, our inquiry into its composition and characteristics collapsed because the competing Soviet moon program collapsed.
Said Burke, The Moon is a natural laboratory for planetary science and a platform from which we can observe the universe. On its surface, the Moon preserves a record of ancient solar system events—events that have been effaced on Earth by geologic and atmospheric processes but whose visible signs have been preserved on Earth's satellite, which has no atmosphere and no weather. According to Burke, the solar wind gets implanted in the lunar regolith—the fine powder that covers much of the Moon's surface—and a thorough analysis of this substance can, some scientists suggest, tell us what the sun was doing four million years ago.
The Moon would be a wonderful place to put all kinds of telescopes, Burke said. Its dark sky screens out competing light rays. Its stability permits extremely sensitive instruments to be operated. A telescope on its surface would not have to peer through distorting atmospheric waves, which is especially important if you want to look at the infrared. Permanently frigid regions would be ideal for infrared observatories—no expensive cryogens needed—to study the formation of stars in the far reaches of the universe. The Moon always keeps the same face pointed toward Earth: Radiotelescopes placed on the far side of the Moon would be shielded from interference caused by radio emissions from our planet. The use of large arrays of linked telescopes would give precise readings of distant phenomena.
Burke explained that the Moon is constantly being struck by meteorites, including tiny space particles that have pulverized much of the surface into the lunar regolith, which looks like dry cement. Oxygen, silicon, and various metals, including aluminum, titanium, and magnesium, abound on the Moon's surface; iron is available in the form of small particles, broken down over the eons by the meteorite bombardment. Burke advocated developing the technology to exploit these resources and to use them in building habitats for lunar construction workers, manufacturing stations, and space equipment.
Solar-wind hydrogen and helium-3 may be important products that could be extracted from the regolith, he reported. Robotics could demonstrate the concept, but astronauts would be needed to refine lunar materials; they could then construct photo-electric arrays to collect solar energy, which, transmitted back to Earth via microwaves, would give us clean, unlimited electric power.
Burke noted that orbiting spacecraft have detected neutron energies indicating that near-surface hydrogen may be present in the Moon's polar regions. Is this the signature of water ice? If so, it is a major resource to be guarded and wisely used. Landed robotic rovers should go into these dark regions and investigate. Burke displayed an artist's conception of a futuristic Moon settlement: a solar collecting tower on a mountain near one of the lunar poles; photovoltaic panels to yield electricity; a solar boiler to provide heat for astronauts' quarters; a solar furnace for high-temperature resource processing; and a buried net of light pipes to support agriculture in an underground base.
Burke advocated building a great archive on the Moon in which to preserve accounts of human history, images of artistic treasures, and a repository of knowledge that could be used to rebuild our civilization if an asteroid hit shoved us back toward the stone age. From the Moon's low-gravity setting, space explorers could launch outward on less-powerful, more-efficient spacecraft perhaps operating on solar electric power and not requiring the use of heavy, hard-to-tote rocket fuels.
While an engineer at the Jet Propulsion Lab, Burke worked mainly on robots. But a robotic program on the Moon should be no more than a precursor to settlement there, he felt. Despite what he saw as a misplaced and limiting emphasis on a near-Earth space station, he said it is a matter of when and not if we settle the Moon.
There's no other way to learn to live in space than to go there and do it.