American Scientist

Mapping Mars. Oliver Morton. xv + 350 pp. Picador USA, 2002. $30.

Mapping Mars covers a lot of ground, albeit on another world. The author, Oliver Morton, aptly describes its contents as follows:

This book is about how ideas from our full and complex planet are projected onto the rocks of that simpler, empty one. The ideas discussed are mostly scientific, because it is the scientists who have thought hardest and best about the realities of Mars. It is the scientists who have fathomed the ages of its rocks, measured its resemblance to the Earth, searched for its missing waters, and—always—wondered about the life it might be home to. The stories they tell about the planet must have pride of place. But there are artists in here too, and writers, and poets, and people whose dreams take no such articulated form, but still focus themselves on the same rocks in the sky.

Over the past few decades Mars, a prime target of NASA's program for exploring the solar system, has been visited by a small flotilla of spacecraft (not always with the intended outcome), and it is a significant achievement to translate their discoveries into plain English. Mars has also been a favorite subject of science fiction writers, as well as scientists and engineers whose ideas are so futuristic that they almost qualify as fiction. Morton's eclectic tales weave together science and imagination seamlessly, and the result is engrossing.

He begins by explaining the importance of maps in exploration, hence the title. His interest in maps may stem from his residence on the prime meridian (Greenwich, England), which plays such a prominent role in terrestrial charts. Mapping another planet is no easy feat, and Morton explains the crafting of the control net—a mathematical corset that holds together the scientific representation of the martian surface—that makes this possible. He also discusses the significance of one landing site to the accuracy of the net, the evolution of naming conventions for martian geographic features, the artistry of airbrush drawing in map construction and the measurement of elevations by an orbiting laser altimeter.

Next comes a historical perspective on Meteor Crater, Arizona, and the role that scientific study of it played in the recognition that impact cratering is a pervasive planetary geologic process. The reader is then treated to a grand tour of the martian surface as seen from orbiting spacecraft—unfortunately, and inexplicably, without benefit of an accompanying map. While reading this elegant description, I found myself constantly referring to the U.S. Geological Survey topographic map of Mars, and any serious reader of this book is advised to acquire a martian map or globe beforehand. Cautionary notes on the interpretation of landforms seen from on high and the value of multiple working hypotheses follow. Morton also discusses the difficulty of portraying artistically various martian geologic features (for example, Tharsis volcanoes, Hellas impact basin, Valles Marineris), because of their monstrous scale.

The third section of the book deals with martian water—or, more accurately, the geomorphic evidence for past water and the mystery of its disappearance. The case for channels carved by flowing water is compelling; that for shorelines defining a possible ancient ocean is less so but still intriguing. Observations bearing on underground water or ice may provide an answer to the question of where the water went. (Modern science fiction takes scientific evidence for water on Mars seriously, and the desiccated nature of the planet's surface is a central theme in most novels set there.) This section is more difficult reading than those preceding it, but the importance of water in geology and biology demands a serious discussion.

The importance of place—that is, landing sites—in exploration is discussed next. Morton makes the case that images obtained from orbit are not as intrinsically captivating as scenes viewed from the ground. This is clearly correct, as demonstrated by the considerable public interest in the Mars Pathfinder lander and its rover in comparison with the limited following of the various orbiter missions (which generate considerably more science).

It's difficult to predict whether the public will take an interest when new methods are eventually applied to map the subsurface in the search for any extant or fossil life. But surely people everywhere will be fascinated when astronauts one day visit the Red Planet, which is why Morton introduces the reader here to Robert Zubrin, an enthusiastic champion of the human exploration and colonization of Mars. If Zubrin's Mars Society has its way, astronauts will soon step onto Mars, and settlements will dot its maps.

The book ends with a consideration of the likelihood of a continuing human presence on Mars. For the most part, this section describes some far-out dreams (mining martian ore deposits for earthly consumption, constructing railways for long-distance travel around the planet and a space elevator for lifting materials out of the Mars gravity well, implementing strategies for terraforming the planet), each so unrealistic that I must admit I lost interest. Blurring the line between science and science fiction, even if only in describing the exhortations of others, is just not my idea of popular science. However, this section will likely appeal to more visionary readers.

The style of the book deserves comment. Throughout, the author introduces numerous scientists, most of whom he interviewed. This gives the story of Mars exploration a human dimension and at the same time ensures that significant scientific contributions are properly acknowledged. These case studies serve to soften the hardcore science and are generally done well, but they are somewhat overused (by my count, Morton features at least 65 scientists).

That criticism aside, there is much to recommend this book. The author has an encyclopedic grasp of the development and major discoveries of Mars science, and he summarizes them in a very understandable way. Morton's treatment is factual and remarkably free of errors. And, I must confess, I am frankly envious of his engaging prose. This book will delight anyone interested in the exploration of the planet next door.—Harry Y. McSween, Jr., Geological Sciences, University of Tennessee, Knoxville