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Review: Astrobiology: A Brief Introduction

Astrobiology: A Brief Introduction
by Kevin W. Plaxco and Michael Gross
The Johns Hopkins University Press, 2006
softcover, 272 pp., illus.
ISBN 0-8018-8367-9

A decade ago astrobiology was still on the fringes of scientific respectability: a new interdisciplinary field that sought to combine disparate fields like chemistry, biology, and planetary science in an effort to search for life beyond the Earth. Today, astrobiology has acquired a sheen of respectability: there are academic programs devoted to the field, a “virtual” NASA institute, and a number of funded research efforts in the field (although NASA funding for many of those efforts are in jeopardy because of budget cutbacks.) However, to many people, astrobiology itself remains something of a mystery. A new book authored by a scientist and a science writer helps describe the scientific underpinnings of this new field.

From the very beginning, Kevin Plaxco and Michael Gross draw a distinction between astrobiology and exobiology, a term typically used synonymously with astrobiology. To them, exobiology is the “science of extraterrestrial life”, while astrobiology “focuses on the more fundamental, and more tractable, question of the relationship between life and the Universe.” That, they believe, opens up astrobiology to the study of life on Earth, which is, after all, the only world in the Universe that to date we know harbors life. That, not surprisingly, begs the question of what is life, which they tackle in the book’s first chapter. Their definition, for the record, is that life is “a self-replicating chemical system capable of evolving such that its offspring might be better suited for survival.”

To them, exobiology is the “science of extraterrestrial life”, while astrobiology “focuses on the more fundamental, and more tractable, question of the relationship between life and the Universe.”

With the definitions of life and astrobiology out of the way, Astrobiology: A Brief Introduction then goes on to examine the issues associated with the formation of life, at least on Earth. Starting with the Big Bang, they work their way through the formation of stars and solar systems, the development of the chemical building blocks of life, and the evolution of life itself on Earth. They also look at the study of extremophiles, life forms that exist under extreme conditions of temperature, salinity, and pH that scientists once thought to be inhospitable to life (and thus expand the range of conditions on other worlds that could support life). Finally, the authors conclude with chapters on the prospects for habitable worlds both in our solar system and beyond, and the search for life on those worlds, ranging from the controversial Martian meteorite ALH84001 to SETI.

Because astrobiology is such an interdisciplinary field, the authors cover a wide range of material in the book, from cosmology to organic chemistry. While many space professionals and enthusiasts may be familiar with the astronomy and planetary science discussions, the biology and chemistry portions of the book may be less familiar, and a bit harder to read, especially for those who never took (or have long forgotten) college biology and chemistry. However, it’s worth it to slog through some of the denser discussions of biochemistry and the like, as the authors have provided a comprehensive yet concise introduction to the field. Astrobiology: A Brief Introduction is a good way to get up to speed with the field and understand the scientific foundation upon which this study of life on Earth and beyond is based.