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Review: The Possibility of Life

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The Possibility of Life: Science, Imagination, and Our Quest for Kinship in the Cosmos
by Jaime Green
Hanover Square Press, 2023
hardcover, 304 pp., illus.
ISBN 978-1-335-46354-8

Prospects for life beyond Earth have varied wildly between two extremes. On the one hand, discoveries ranging from the thousands of exoplanets in our galaxy to extremophile life on Earth make it seem, for many, that life may be commonplace in the universe provided the right combination of ingredients—organic compounds, water, and energy—is present. On the other hand, we have yet to find any evidence of extraterrestrial life, including decades of searches for radio signals and other technosignatures of intelligent life.

An astronomer says, only half jokingly, “we know less about exoplanets now than we did before we started discovering them,” as discoveries upend models of solar system formation.
That gap between potential and evidence is a challenge and opportunity for the still-nascent field of astrobiology. After decades of research, scientists are only now beginning to come to grips with the scope of the challenge: finally knowing what they don’t know. That’s the message that emerges from The Possibility of Life by science writer Jaime Green.

The book is a collection of interconnected essays on various topics associated with the search for life beyond Earth, from biology to astronomy to technology. Green thoughtfully explores those topics, talking with many scientists involved in those various fields. That’s combined with perspectives from science fiction, with a mix of obvious choices (The Star Trek franchise, Contact, and Arrival) and lesser-known ones, like the novel The Sparrow about meeting intelligent species on a planet in the Alpha Centauri system.

One theme that emerges from this book is that scientists are just beginning to understand the scope of the challenge of finding life beyond Earth. One biologist studying the origins of life says that our knowledge of life as a phenomenon is “right now where we were with gravity before Newton:” we can see it, but don’t know the underlying principles. Another astronomer says, only half jokingly, “we know less about exoplanets now than we did before we started discovering them,” as discoveries upend models of solar system formation.

Such awareness is, arguably, a sign of a maturing field, coming to grips with what it doesn’t know in order to fill those gaps. Confidence abounds in some parts of the field: speaking on a panel two weeks ago at the 38th Space Symposium in Colorado Springs, Pete Worden, former head of NASA’s Ames Research Center and current executive director of Breakthrough Initiatives, predicted by 2050 we would have evidence that life was commonplace in the galaxy and even may have detected the first signals of extraterrestrial civilizations (one of the efforts that foundation supports is a SETI project, Breakthough Listen.)

Yet, it’s also possible that by 2050 scientists are still debating whether ancient materials in Martian samples, or a faint spectral signature of an “Earth-like” exoplanet, constitutes evidence of life. By the end of the book, Green, like one of the scientists she interviewed, has come to believe that finding life elsewhere is not the goal so much as appreciating the life we know exists here on Earth. “It wasn’t life elsewhere that held the magic, anymore,” she concluded. “We were just as improbable, and as important, as whatever we hoped might exist on worlds beyond.”

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