Special Report

Sara Seager’s Tenacious Drive to Discover Another Earth

Planetary scientist Sara Seager has turned tragedy into tenacity in her search for new Earths among the stars

(Trent Bell)
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With two young boys at home and her husband gone, Seager flipped her life around. Her greatest thrills previously came from wilderness adventures. Now, she directed her energies into her research with a new sense of purpose. “I’m dedicated to finding another Earth,” she says, “because what else can I do?”

NASA’s Kepler space telescope with its bulging catalog of exoplanet discoveries is just a baby step toward Seager’s big goal. Most of the worlds found by Kepler are too distant and dim to study in detail; that’s why Seager is working on TESS, which will scan the sky, starting in 2017, for planets orbiting closer, brighter stars. The James Webb Space Telescope—an $8.8 billion successor to the Hubble telescope, set for launch in 2018—will peer through the atmos­pheres of some of those worlds, using the approach Seager pioneered in her graduate school days. But even those tools aren’t enough.

Tracking down our planet’s twin will require three breakthroughs: Understanding the “biosignature,” or chemical fingerprint, of alien life; locating the best exoplanets to examine for fingerprints; and developing a way to examine those planets directly, with extreme precision.

Strange as it sounds, modeling the chemistry of alien life is the easy part: It requires only brainpower, not hardware. In a recent paper, Seager explores which of the molecules given off by Earth’s biomass would be detectable on other planets. In another, she considers one specific type of atmosphere, dominated by hydrogen.

Next comes locating the most promising exoplanets. Earth is tiny compared with the Sun, and it completes an orbit just once a year. To identify an identical planet around another star, you need to look at a lot of stellar targets for a very long time. For Seager, it’s not about spending long nights with a telescope, but about interpreting incoming data and coming up with concepts that make the observations possible.

Sitting beside us on her office windowsill is one of these concepts: a prototype of a miniature satellite called ExoplanetSat. It is designed to be produced in batches, with copies costing a million dollars or less. A fleet of ExoplanetSats, each about the size of a loaf of bread, could provide a low-cost way to scan the sky.

Finally, there is the colossal challenge of bringing those alien Earths into view—of finding a way to blot out the star and get a direct look at the dim planet right alongside. Doing so will require a totally new kind of observatory. “All my activities are funneling toward a big, direct imaging space telescope,” Seager declares.

NASA recently invited Seager to lead the planning of a Starshade mission. A screen, shaped like a set of flower petals, would fly thousands of miles in front of a space telescope and eclipse different stars as needed. She accepted instantly, ending a two-year recovery period when she turned down almost every new professional offer. “When they asked me to be the chair I could do it, because I had said no to everything else,” she says. If NASA got an extra billion dollars, Seager says her team could begin building tomorrow. But if NASA doesn’t get the money, she has other plans.

The ExoplanetSat project brought Seager in contact with Planetary Resources, a private company that wants to mine the rocky asteroids circling near Earth. She started thinking that rich, space-minded patrons might want to underwrite her search. “I have a private thing going on, a company called Nexterra, as in ‘next Earth,’” she says. “Or maybe I’ll become wealthy and I’ll support my own Terrestrial Planet Finder.” I look at her sharply and see she is serious. “The only way I could make the money that I’d actually like is really asteroid mining. It sounds like a long shot, but you know what? They’re all equally long shots.

“This is what I hope to do in my lifetime: I hope we’ll get 500 Earths. If we’re lucky, maybe 100 of them will show biosignatures.” It takes a moment for the sentence to sink in. She is talking about 100 planets with signs of alien life.

I put down Seager’s ExoplanetSat mock-up and take a tour of the strategic totems in her office. A copy of her book Exoplanet Atmospheres; yes, she wrote the book on the new field. Champagne bottles from when her PhD students graduated. Another champagne bottle, celebrating Seager’s 2013 MacArthur fellowship—better known as the “genius” award. A photo of a man standing next to a telescope. “This is my boyfriend,” Seager explains, without changing cadence. “I’m completely crazy about him. It’s like the romance of the millennium. But how do I fit him in my life now? He also lives in a different city. I’m figuring it out.”

I’m still trying to figure out one thing about Seager. Normally, at some point in a conversation like this, I hear a philosophical gush about what the discovery of alien life would tell us about our place in the universe. She nods. “That’s not why I’m doing it.” What about being a part of history? “That’s cool, right? That’s not really why I do it, but if someone wants an answer, I usually try to give that one.”

Even with all that she has revealed, I am struggling to get behind the mask. Then I realize how much of her life is defined by the Before and the After. I’ve never met the Before Seager, the thrill-seeker who paddled through rapids with Wevrick in a single canoe with limited supplies, in waters far from human habitation.

“I think I do it because I was a born explorer,” she says after an uncharacteristic pause. “If I was born in the past, I probably would have been one of those guys who made it to Antarctica. I start a project and I get really excited about it, the heart beats faster. I just love what I do.”

About Corey S. Powell

Corey S. Powell is Editor at Large at DISCOVER magazine and the acting Editor in Chief of American Scientist magazine. He spends a lot of time tweeting about the dark corners of the cosmos.

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