National Geographic
Emerging Explorer

Jeffrey Marlow

Geobiologist, Writer, and Educator

Picture of Jeffrey Marlow

Photograph by Sam Cossman

Probing the limits of life on Earth, and beyond

Geobiologist Jeffrey Marlow’s curiosity has led him everywhere from the edge of a volcanic lava lake in the South Pacific to the bottom of the sea. He studies the microbes that inhabit such extreme conditions in an attempt to chart biology’s outer limits.

The work could inform questions about life elsewhere in the solar system, such as Mars, but it also has very down-to-Earth implications. As a postdoctoral fellow at Harvard University, Marlow is studying how to use microbial metabolisms from the deep sea to turn the potent greenhouse gas methane into biofuel.

As if this weren’t enough to do, he is also a journalist and educator with bylines at publications including the New York Times, Wired, and Discover magazine. He wrote and directed a short film about NASA’s Mars rover Curiosity. And he’s launched an educational outreach project, Mars Academy, aimed at igniting an exploratory spark of inspiration among marginalized students around the world; he recently returned from the project’s initial effort in Rio de Janeiro’s City of God. —By Christina Nunez

“Realizing that there’s something so magical and adaptable and unknown about life, that it’s a fundamental and unsettled aspect of our world, created an element of mystery that I had to chase down.”

—Jeffrey Marlow

Why is it important to study these tiny, hardy life forms? Why are microbes so compelling, scientifically?

One reason is that they run the planet. Microbes make more than half of the oxygen that we breathe. They mobilize nutrients all over the place that enable higher forms [up the food chain] to exist. So they really are the basis of life on Earth; that’s kind of the practical side of why they matter. The other aspect is just the essential mystery of life: the question of whether we are alone in the universe, and the idea of finding other types of biology, whether or not we would recognize them in the canonical form that we know here on Earth. Life is such an interesting entity that we are still struggling to define, but it’s so meaningful at some kind of essential level. Looking for that same kind of system elsewhere is an essential human question, I think.


What first drew you to these topics?

The microbiology aspect stemmed from a family trip to Yellowstone, for sure. I remember seeing these beautiful, crazy, dangerous hot springs with all these amazing colors. When someone told me life could exist in that, I was stunned and just needed to know more. What are the limits of biology? Realizing that there’s something so magical and adaptable and unknown about life, that it’s a fundamental and unsettled aspect of our world, created an element of mystery that I had to chase down.

The other experience was witnessing a space shuttle launch. Seeing this rocket so powerfully escape the atmosphere and transport people to an entirely different realm was amazing to me. Realizing there’s a microscopic world that we know so little about, and a much larger interplanetary world that we know so little about: Where do those two intersect? That’s kind of what I’m after.


Why have you decided to write about science yourself rather than just doing the science and giving interviews about it? Do you think that will continue?

From a selfish perspective, it’s just a great way to learn about new things. I can essentially talk to anyone in a different field and learn what they’re doing and why, and then share that perspective with a larger audience. I also think that having a technical background is useful in demystifying some problems with science communication. I can kind of evaluate scientific claims that some people are making and I can ask slightly more detailed questions that might illuminate a new side of the research that the scientists themselves might not quite be comfortable trying to explain. It’s a way to exercise my curiosity in a new way, and it’s actually informed and improved my own research in some surprising ways.


What are the next steps for you? What do you hope to achieve in the long term?

Understanding the limits and roles of microbes throughout the planet’s biological system is a rich research area with a lot of potential. Specifically, with genetic sequencing over the last several years we’ve massively expanded the number of documented microbes, their habitats, and some idea of what they could be capable of. The next frontier is to understand what they’re actually doing, and how they modulate the biosphere. In the long term, I would love to bring this work at the limits of microbiology to space and astrobiology.

I’ve also started a project called the Mars Academy with a few other scientific colleagues. It’s about using scientific inspiration to kick-start an interest in exploring your surroundings and following your curiosity to be more engaged in the educational process. So for me, it was a space shuttle launch or that trip to Yellowstone that turned me into a scientist. Most scientists have similar stories—there’s one spark that lit that fire of curiosity. It seemed like promoting similar experiences for others who may not really see the long-term value of an education could be an efficient way to turn students into active and eager learners in a lot of different contexts.

We had our pilot project in the City of God in Rio de Janeiro last year. Alongside local scientists, we taught kids a little bit about the scientific method and space exploration; we went out to a local island and wandered through the forest, just kind of seeing what caught their eye and what they wanted to know more about. Then they had a chance to select a few locations on Mars that the NASA HiRISE imager would take pictures of. It was just amazing to watch their faces light up with this new sense of curiosity. Several kids said it was one of the best weeks of their lives, which was very humbling and gratifying, but also sort of insufficient in a lot of ways. Those first reactions were great, but we’re tracking things long term, seeing where we can help out in the future, and how scalable this idea could actually be. It’s just really exciting to share that love of exploration that got me into this field with other people who might not otherwise experience that kind of inspiration.

Conversation has been edited for length and clarity.

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