Review of Alien Earths: The New Science of Planet Hunting in the Cosmos by Lisa Kaltenegger

Space is so cool, and I love reading books that explain how we learn the stuff we know about space. That’s exactly what Dr. Lisa Kaltenegger delivers in Alien Earths. This is the story of how we look for exoplanets—worlds orbiting stars other than our own Sun—and specifically, how we might determine whether those exoplanets can support life similar life on Earth. Along the way we learn, as Kaltenegger did, so much more about life on Earth, its possible origins, and what makes our great blue marble so special. I received a review copy from NetGalley and St. Martin’s Press.

Kaltenegger takes us through the steps required to understand the science she does. She starts with essential questions, like the conditions required for a planet to be habitable, to the very concept of “what is life?” She explains some of the basics of merely locating exoplanets, but what this book provides in more detail is the trickier project of ascertaining those planets’ habitability. For this, Kaltenegger dives into the science of simulations and describes how she and her interdisciplinary team built physical labs to test and simulate different phenomena. These phenomena are often coincident with life, and by understanding how they occur and what signs—like spectra—they give, Kaltenegger and her team could build computer simulations to help them understand how planets like Earth might appear to a telescope dozens if not hundreds of light-years away.

Kaltenegger herself is interesting. An astrophysicist and engineer, she brings a unique perspective that is only enhanced by her natural appreciation for the contributions of other branches of science. Her work requires knowledge of geology and geochemistry, of physics and mathematics and computational methods, of environmental science. I admire her willingness to collaborate and cooperate, and one of the most consistent themes to emerge from Alien Earths is the importance of science as a collaborative effort.

The writing and storytelling are serviceable—Kaltenegger tries her best to weave some of her personal life throughout the book, a way of creating a human connection to this cosmic story. It’s neat, and I especially hope that younger women and girls who read this are inspired by her story. However, if you are looking for a gripping narrative to go with your pop science, you won’t find it here: Alien Earths is much more descriptive and expository. That’s not a bad thing!

Indeed, my favourite thing about this book is just how enthusiastic Kaltenegger is about life her on Earth! Whether we’re talking the extremophiles who live around the smoke-stack like vents on the ocean floor to the tardigrades all the way to extinct megafauna and everything in between, Kaltenegger is here for it. Her enthusiasm is infectious and demonstrates how important this science is: by looking for life out there, we better understand the story of life here.

I’m a smart cookie, yet frankly, I’m not sure I could ever be an astronomer or astrophysicist. It is miraculous to me that someone can stare at data coming in from a telescope, at the wobbling of a blurry little point of light or spectral lines, etc., and conclude, “Planet.” Let alone the follow-up conclusion of “could be Earth-like!” Like, wow. Honestly, the things that scientists can do these days—not just with our technology but with our sheer imaginative design of experiments … it’s staggering. And humbling.

Alien Earths is more than informative; it is a reminder of the value of science, collaboration, and deep thought. It is a love letter to life here on Earth in all its diversity, and it’s a thoughtful exploration of the question we’ve been asking since we could ask questions: are we alone?