As I read this book about finding life in unexpected places, I was reminded of a Star Trek episode, “The Devil in the Dark.” Kirk, Spock, and crew encounter a silicon-based life form living deep in the rock of an alien planet—totally unexpected and totally foreign. Yet, by the end of the program, the Star Trek crew come to understand the Horta, as the life form is called, and they even collaborate with it to find valuable mineral reserves buried deep in the rock of the planet. Deep Life concerns the search for life in a place where no one would expect to find life: in the subsurface rock of Earth. Author Tullis Onstott, a geomicrobiologist, writes:
The author introduces the scope of the book by posing questions related to the extent of subsurface life, the depth to which this life can be found, the lifespan of subsurface life, the...