After reading this book I can understand why there should be a strong emphasis for the manned exploration of Mars and why Mars should be the focus of our attention. By comparison manned exploration of the moon is really not that important. The moon does not have resources that can easily be exploited. It does not have an atmosphere, oxygen is not easily extractable from the lunar rocks, and there is no carbon in the environment. Even the lunar night/day cycle is not conducive to growing plants.

The book is long at about 350 pages. But, it starts out in an exciting way in the first chapter, which is only 18 pages long, with a manned Mars Direct program starting in the year 2020 and costing only 30 billion dollars to develop. Using current technology and a heavy-lift vehicle about the size of the Saturn V, a sequence of launches is started. The first launch is unmanned and carries a nuclear reactor as a power source and 6 tons of liquid hydrogen. After landing on Mars this hydrogen is converted into 108 tons of methane and oxygen from the Martian atmosphere (95 percent carbon dioxide) using gaslight technology and the nuclear power source.

This is enough fuel and oxidizer to provide land propulsion on the Martian surface and a trip home for the four astronauts that arrive about three years later using a similar size launch vehicle. Herein lies the key for the proposed Mars Direct program - to utilize as much as possible the Martian resources that are available.

Like early explorers that came to America, who didn't carry their air, food, water, and fuel with them to live permanently in the New World, so Martian explorers will use the resources of Mars. Even the thin Martian atmosphere, which is equivalent to the earth's atmosphere at about 100,000 feet, can be used for aero-braking. In fact, taking into account the Martian aero-braking and surface refueling, it is more efficient in terms of mission delta velocity requirements to go to Mars first and then go to the Moon rather than go to the Moon directly. Naturally, this route takes more time, but it is more efficient in terms of delta velocity.

For a cost of about $3 billion per year a four-man crew and a Martian habitat can be sent annually, building up a Martian base. Problems like radiation and zero gravity en route can be overcome and are not show-stoppers. Eventually, air-bubble shelters could be built to provide a shirt-sleeve environment using nuclear power and carbon dioxide in the atmosphere to make oxygen. The carbon dioxide can also be used to reduce iron oxide to make iron.

Using different processes other raw materials can be made. In the long-range view, Martian terraforming may be a real possibility provided there is enough carbon dioxide in the Martian regolith (soil, rock, etc.). It may be possible that by raising the Martian atmospheric temperature by a relatively small amount, enough out-gassing from the regolith may be available to raise the Martian atmospheric pressure to some appreciable fraction of one Earth atmosphere in 1,000 to 2,000 years. This could be accomplished by putting solar mirrors in orbit aimed at the Martian poles. Such an atmosphere would allow humans to walk on the Martian surface without a pressure suit, although a breathing apparatus would still be required. However, since the Martian day is only 40 minutes longer than an Earth day, plants would do just fine in the carbon dioxide atmosphere.

This is an exciting book to read and a "must-read" book for any space enthusiast. Real manned exploration in our solar system takes on a new meaning in this book.