MINING THE SKY

This book complements Dr. Lewis' previous work, Rain of Iron and Ice. In that volume, the hordes of bodies meandering around our solar system were portrayed as similar to the mythical Sword of Damocles — threats hanging over all our heads. Here, instead of a threat, they become a promise — the proverbial pot of gold.

Of course, the asteroids and comets, as a group, present both possibilities. From them, as well as gold, we might obtain structural metals like iron and nickel. Precious metals like the platinum group also are present in vast quantities — as are water and simple organic compounds. In fact, gold is probably one of the least valuable constituents of these bodies.

The planets offer a different sort of treasure trove. Mars has plentiful carbon dioxide, which can be made into rocket fuel. Like the moon, it has another precious commodity that is often overlooked. This is just the rock and dirt which can be used to cover habitats, forming a shield against radiation and micrometeoroids. At a slightly more advanced stage of development, rocks can be processed into bricks and cement, or oxygen, iron, aluminum and silicon can be extracted from them. (Although he speculates about water trapped in the form of ice at the poles of the moon, Dr. Lewis could not then know of the March 1998 preliminary results from the Lunar Prospector mission which indicate that this is present in useful amounts. If so, the other lunar resources become far more accessible.)

The moon is unique among solid bodies in having helium-3 in useful concentrations. This material, deposited by the solar wind, clings to mineral grains in the lunar regolith. If extracted and separated from the other trapped gases, it potentially can serve as fuel for fusion reactors. The upper atmospheres of the giant outer planets represent an even better source of helium-3. Most of the resources will be used where found; in general, it is not economical to return processed materials to Earth. Helium-3 is probably the only exception. Thus we can, with clever designs, bootstrap our way out into the solar system. The key is lowering the cost of reaching low Earth orbit. Dr. Lewis foresees that dropping quite soon to reasonable levels.

Dr. Lewis opens each chapter with a fictional scenario that illustrates some aspect of this process of solar-system development. The chapters then describe the details of the processes in clear, factual terms. The language is not extremely technical, but there is a lot of information packed into these 274 pages. In the last two chapters, he permits himself some philosophy as he discusses the implications of his ideas for the environment of Earth and the future of humanity. The paperback edition contains a new afterword with news of the Mars Pathfinder mission and other recent events. A suggested reading list, a glossary, and an extensive index round out the useful and optimistic book.

There is one goof. On page 180 is the sentence: "But still it would appear to make little economic sense for an Earth-to-Mars vehicle to waste the fuel needed to stop in at Mars." He means "Earth-to-Belt".

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This page was last modified on 11 July 2014.