‘We’re Close’: SETI Astrobiologist Nathalie Cabrol on the Search for Life

A leading astrobiologist combines her passion with the weighty nature of trying to answer two big questions: Are we alone in the universe? How did life on Earth originate in the first place?

Nathalie Cabrol's book, "The Secret Life of the Universe: An Astrobiologist's Search for the Origins and Frontiers of Life" (Scribner/Simon & Schuster), published last month, offers an illuminating and reflective look at the search for life. It is a mind-expanding quest that takes place not only "out there" but also here on Earth.

Perhaps part of the challenge is that humanity is both the observer and the observation, Cabrol explains. That is, we are life trying to understand itself and its origins. "We are reminded that the universe is both an enigmatic puzzle and a deep mirror reflecting our own existence," Cabrol writes.

The Secret Life of the Universe: An Astrobiologist's Quest for the Origins and Limits of Life: $25.99 at Amazon SETI's Nathalie Cabrol, one of the world's leading astrobiologists, takes readers on a mind-bending journey through the universe to explore humanity's most burning questions: Are we alone in the universe? How did life on Earth originate? View Offer

Nathalie Cabrol is a French-American explorer and director of the Carl Sagan Center for Research at the SETI Institute in Mountain View, California. In an exclusive interview, Space.com spoke with her about her new book and the professional odyssey she has embarked on.

Space.com: Your book is made up of a dozen unique chapters-is there a theme that connects them? Perhaps in the topics you covered, you were on your own personal journey to help recognize the issues surrounding the are we alone question?

Nathalie Cabrol: The question behind each chapter is that we are searching for something we don't understand. It's a reference point that this is us. And that's okay. It doesn't matter that we don't have the answers. Because if we did, we wouldn't be making the journey.

Space.com: So that journey is open and we have to be open to surprises?

Karol: The chapters are the journey. Each chapter helps you see a different perspective, a different angle, a different light on a question. I don't necessarily believe in the way we're going to approach life in the universe right now. I'm very open about that. But this is where we are and this is what we have. The missions tell us that the stuff we're made of is not an accident. It's almost normal out there. I wanted to share at the same time that there are unanswered questions... to show that maybe there are other ways to explore life.

Space.com: You write about Mars and the long saga of searching for life on the Red Planet, highlighting in particular the Viking Labeled Release (LR) experiment of the 1970s, results that you still consider inconclusive today.

Karol: Yeah, it's not conclusive and just an acknowledgement that five decades later people think it showed that there was life on Mars. We have evidence today that those results could have been achieved without life and just by the environment. That [evidence] says we haven't shown that there was life. You have to show that the environment alone didn't produce those LR results. Environment and life...how do you disentangle the two and come up with an unambiguous signature of life? If there's life somewhere, you don't have one or the other. You have co-evolution, a mixed thing, a living world.

Space.com: Is the search for life on Mars a blueprint, a teaching tool, for the search for life elsewhere?

Karol: It depends on the scenario you choose. Scenario 1 is that there is no life on Mars, period. The problem for us is going to be proving that. In science, this is the hardest part - when do we pull the plug and just admit that there is no life on Mars and be sure of it.

Scenario 2 is that Mars has life, but unfortunately we somehow contaminated each other through planetary exchange. So it's probably related and doesn't teach us much about other forms of life.

Scenario 3 is that life on Mars has a separate origin process.

Mars can teach us general rules for looking for life elsewhere, and especially the relationship between life and the environment. It will certainly teach us general rules for co-evolution. Can it teach us how to look for life on Titan or Venus? I don't think so. Those environments are so different.

Space.com: There is growing interest in the possibility that Venus could be an incubator for life.

Karol: If we find life on Venus, that's extraordinary, because this is pretty much the anti-Earth, a dry, super-hot, super-acidic environment. But the point is that we're exploring these worlds and we're learning about very different potential co-evolution. We're looking for the complexity of life affecting its environment and the environment affecting life.

Ruimte.com: While reading your book, something else struck me: we are all young people when it comes to fitting together the puzzle pieces of the search for life.

Karol: We are so young. I was born in 1963. Just a few years before that, we only knew about the universe through ground-based telescopes. My childhood [saw the] Mariner spacecraft hurled to Venus and Mars. Since then, in just 60 years, everything has literally taken off.

We are very young and the search for aliens is the same. We are just beginning to learn what the universe is about, the diversity. What people are missing is the iteration of science. You ask a question. You come up with an experiment. You test it. Then you have the science and it is not at all what you predicted. Now you have to mix it up and make sense of it. Come up with another hypothesis. Come up with more experiments and test them. And that is what we do.

Space.com: When do you think we'll find life?

Karol: I get that question quite often.

I will tell you we are close. I really think we are close. Exoplanets are going to be tricky. They are so far away. We don't know where life is and we can't bring back samples at this point. Maybe we can find traces of contamination and synthetic molecules to make sure we find life.

As for SETI, that could happen at any moment and anything could land on our planet at any moment.

Space.com: And that brings me to your chapter, "Connecting Blue Dots," which looks at, among other things, unidentified flying objects (UFOs), which in some circles are now also called unidentified aerial phenomena (UAPs).

Karol: We are looking for aliens in the kind of world that we understand, a world of space and time with the laws that we know. And in a universe of space and time, there is much to be said about sending robots, that the first encounter will be the technology of another species. If they are organic like us, then they are vulnerable like us.