THE HUNT FOR LIFE ON MARS

Goldsmith (who edited the 1991 PBS series on astronomy and wrote its companion volume, The Astronomers) reports on the biggest science story of 1996: NASA's claim to have discovered that life once existed on Mars. The fuss is over ALH 84001—the first meteorite discovered in the Allan Hills of Antarctica in 1984. ALH 84001 had generated considerable excitement even before the NASA announcement, because, at 4.5 billion years, it is the oldest extraterrestrial rock ever found. (Goldsmith fascinatingly explains how the knowledge gained from another Martian rock, EETA 79001, allowed scientists to establish radiometric dating for ALH 84001.) Ancient life was suggested when carbonates, or sedimentary elements, were found within the otherwise volcanic ALH 84001, and still further studies revealed the now-famous, microscopic ovoids that seem to resemble bacteria. If the ovoids were once alive, however, they were smaller than anything ever discovered on Earth, and, the scientists who examined ALH 84001—astronomers, geologists, and chemists rather than biologists—reported no cell walls or cellular byproducts. The lack of biological evidence led the eminent biologist Edward Anders, whom Goldsmith colorfully describes and quotes at length, to say, ``This is half-baked work that should not have been published.'' Of course, the researchers never really claimed to have found life, only its suggestion, and the media quickly distorted the story, but Anders makes strong arguments. At most, ALH 84001, because of its carbonates, may only prove that liquid water once existed on Mars. That fact alone makes it a remarkable rock. Goldsmith interviewed every principal and has a great ability to write entertainingly without dumbing down his material, but the story of ALH 84001 is an unfolding one. His book will have a short but vigorous life, the best account available until new ones supersede it. (15 b&w photos, not seen) (First printing of 40,000; Book-of-the-Month Club/Quality Paperback Book Club selection)