The Secret Life of the Universe: An Astrobiologist’s Search for the Origins and Frontiers of Life by Nathalie A. Cabrol

Discouraging recap of our quest for certainty

Nathalie A. Cabrol, a French-American astrobiologist, is the director of the Carl Sagan Center of the SETI Institute (SETI = Search for Extraterrestrial Intelligence). She is very much qualified, therefore, to write about the latest research on extraterrestrial life. Her book The Secret Life of the Universe was published in 2023. These days, it’s hard to keep track of all the piecemeal press releases about exoplanets, unmanned space probes, Mars rovers, and such. I hoped to find in Cabrol’s book a comprehensive and intelligent recap of what we know about the possibilities of life within and without our solar system. She does a fine job of summarizing the present state of knowledge in this area. This book is generally organized from the Earth outwards, from Venus and Mars to other bodies in our solar system, and then on to the recently discovered exoplanets beyond.

Although we’re talking about other planets and stars here, astrobiology relies much on geology and meteorology—the workings of water, ice, gases, volcanism, and plate tectonics, for example. Since the life forms are unknown, Cabrol’s work, at least as revealed in this book, is more about studying environments that might be conducive to life rather than speculating about the life itself. She has deliberately written this book to be accessible to a wide audience whenever possible. In general, the text is less challenging than articles in Scientific American or National Geographic; it’s more on the level of USA Today. There are passages, however, where complex chemistry can’t be dumbed-down enough, and the lay reader may find it tough going.

In addition to filling Sagan’s role at SETI, Cabrol also tries to fill his shoes as an inspirational science communicator, but she is less successful at that. This book is educational, but it doesn’t generate a lot of excitement or a great deal of hope. As someone who cares about science and wants to learn more about the universe, I am hopeful that in my lifetime we will discover extraterrestrial life—by that I mean evidence of microbial life elsewhere in our solar system. After reading Cabrol’s book, however, I doubt that’s going to happen anytime soon. She points out lots of possibilities for life in our solar system, but also gives plenty of examples of why confirmation is impossible. We’ve had landers on Mars for 50 years, and we still don’t have a definitive yes/no answer on life there. For almost every other body in the solar system, Cabrol says again and again that there may be life miles beneath the surface. Given how many years and dollars it takes to develop exploratory space missions, it’s unlikely we’ll be digging that deep in the near future.

Exoplanets, and their diversity of environments, offer more hope of finding life of some kind, at whatever stage of development, but we’re nowhere close to sending a probe over light years of distance. Our only hope of discovering interstellar life is if it discovers us first. Cabrol briefly discusses UFOs, or UAPs, but that’s really outside the scope of this book, and she’s a skeptical in that department. More coverage is given to the SETI program, which is actually a number of different programs under the SETI umbrella. Not much luck there yet, either. Cabrol then goes from disappointing to depressing by closing the book with an environmentalist tirade that reminds us that we’re on the verge of rendering ourselves extinct anyway.

Scientists who take on the role of educating the public—Sagan, Neil de Grasse Tyson, Bill Nye, and so on—generally try to inspire a sense of awe and wonder in the reader, hoping to spark their interest in the workings of the universe. Cabrol tries to do the same here, but this reader was just left feeling hopeless and kind of bored.