"It occurred to me, nobody had ever seen things like this before," Zuber recalls, sitting in her office with a commanding view over the Charles River and the Boston skyline behind her. "If you look at something nobody has looked at before, and you have the skills to analyze it, you could make a killing." New views of uncharted worlds offered a great chance for scientific paydirt.
She's been mining that vein ever since, devoting herself to looking at the planets and moons of the solar system in new ways. She has pioneered the use of laser rangefinders for planetary research, to map their surfaces with unprecedented accuracy. She's also worked on the development and operation of a variety of other instruments, including gravity sensors, to probe the hidden past and deep interior of the moon and planets.
These projects all revolve around a common theme — trying to understand what makes planets tick. How did they form and evolve? What processes have affected their changing atmospheres, their growing and crumbling mountain ranges and volcanoes, the appearance and disappearance of oceans, the incising of deep canyons and valleys, the vagaries of unexpected weather and climate changes? Zuber desperately wants to know.
Last year she was selected by NASA as the first woman ever to head a major planetary robotic research mission: the GRAIL (for Gravity Recovery and Interior Laboratory) mission, to be launched in 2011, whose twin satellites will use sensitive measurements of variations in the pull of gravity as they orbit to study the moon's interior, in order to learn about its early history. That's on top of the four ongoing missions she's involved in — on three of them, as leader or co-leader of teams operating specific instruments — that are studying the moon, Mars, and Mercury, and on their way to the asteroids Ceres and Vesta.
Zuber, who has been teaching at MIT since 1996, is "an inspirational leader of scientific and engineering teams who are developing missions and instruments to explore our solar system," says Charles Elachi, the director of NASA's Jet Propulsion Laboratory, where most planetary missions are managed. She is also "a world-leading planetary scientist and educator," he says.
Genes for space
Zuber says she thinks her celestial fascination is "genetically wired in," although neither of her parents, nor her three brothers and one sister, have any particular interest in science. "I spent a lot of time with my grandfather" while growing up in rural Pennsylvania, she says. He had a deep interest in telescopes and skywatching, though he had quit school in 8th grade to go to work in the coalmines. "He had a passion for it. I'm convinced there's a recessive gene for space exploration in my family."
Zuber started building her own telescopes when she was 8, and grinding and polishing her own telescope mirrors when she was 10. She helped pay her way through college by operating a telescope on weekends for visitors at the Franklin Institute in Philadelphia. She applied to graduate school in astrophysics, but ended up switching to geophysics and became the first person from her high school ever to earn a PhD.
Her doctoral thesis, about the ways the surface layers of planets can become twisted and deformed, was purely theoretical. "There wasn't a data point in it," she says. But by the time she had finished it, she realized that the kinds of observations that were needed to carry the work forward — to study the actual surfaces of Mars and other planets with enough detail to see evidence of the processes she had modeled on a computer -were not being done. "I decided to do it myself," she said, hastily adding, "well, with the help of hundreds of people."
Soon after earning her doctorate from Brown University, she became co-leader of a team at Goddard Space Flight Center designing the first laser altimeter system for Mars. It was launched on the Mars Observer mission in 1992, which failed after months of interplanetary travel, losing all radio contact just three days before it was to go into orbit around the red planet. It was a devastating loss for NASA and for the dozens of planetary scientists involved, but an especially bitter pill for Zuber, since it was her first chance to take part directly in planetary exploration.
But the team plugged away, and found a way to incorporate a backup of the instrument onto a new, much less expensive mission. The laser altimeter was re-launched successfully on Mars Global Surveyor in 1994, and has provided the most detailed views of that planet's topography — more detailed, in fact, than then-current maps of certain parts of the Earth.
Despite previous planetary missions that had photographed the surface features in great detail, the altimetry revealed a significant surprise. In a paper that was featured on the cover of Science in 1999, she and her team described the discovery that most of the surface of Mars has a pronounced tilt to the north: that many of the craters, basins and channels were linked and provided a planet-wide drainage pattern — if there was ever water to drain — that all led toward a huge, deep basin that takes up most of Mars' northern hemisphere, and where some scientists have suggested an ocean once stood. And that basin, the lasers showed, has the smoothest surface ever seen in the solar system, as might be expected of the floor of an ancient, long-gone sea.
Prime time for planets
After three decades of involvement in planetary science, Zuber feels that the field is more exciting now than it's ever been, with the possible exception of the period in the 1960s when the theory of plate tectonics was revolutionizing terrestrial geology. There are more missions of planetary exploration going on at once than ever before, and she feels the subject has become more relevant than ever.
"The things we study are not only interesting in their own right, to understand the world we live in, but they are also of very high societal relevance," she says, because of their connection to high-stakes issues including climate change, energy supplies, and resource depletion. "We need a better understanding of the subsurface of the Earth," she says, in order to know how to store nuclear waste safely, to explore for oil and other fossil fuels more efficiently, and to understand the potential as well as the risks for storing carbon dioxide deep underground instead of releasing it into the atmosphere.
This year, Zuber began a second stint as chair of the EAPS department. Until the GRAIL mission was selected, she maintained a full teaching schedule, unlike many department heads, and she advises a large group of graduate and undergraduate students. She's frequently called by NASA to take part in press conferences reporting new results from the various missions she is involved in, including two this year on the initial findings from the MESSENGER mission to the innermost planet Mercury — the first mission to that planet in more than three decades. She has been called to testify twice in the past year before Congress about the future of NASA and how to set priorities for the agency.
But it's the actual robotic exploration, the discovery of new facets of the surprisingly diverse worlds around us, and the endless work needed to make those discoveries possible, that still drive her.
Sometimes that work is an adventure: Over the summer, in preparation for the arrival of the DAWN mission next year at the asteroid Vesta — at about 330 miles across, the second-largest of the asteroids, with an orbit more than 120 million miles beyond Earth's — she led a team of scientists who went to Iceland to study glacial-volcanic features that may resemble what will be found on that volcanic world's surface. "I was with a bunch of astronomers, some of whom had never looked at a rock before," she laughs.
Sometimes, it's the hard work of coordinating a large team to solve the myriad problems that arise in implementing a spacecraft mission: Every day, she spends time working with members of the team preparing the half-billion-dollar GRAIL mission for its 2011 launch. "I spend a lot of time worrying about budgets," she says, but she's confident the team can handle problems and issues as they arise. "I don't micromanage. They know what needs to be done, and I don't tell them how to do it." On the other hand, "these guys know I don't like to be surprised. It's important to talk about problems early."
But in the end, there's the fun stuff.
"Every day I see data that we collected at the moon yesterday that nobody's ever seen before," says Zuber of her role as lead scientist for one of the instruments on the Lunar Reconnaissance Orbiter that is now mapping the moon in unprecedented detail. "I never get over the thrill of getting to know something nobody else knows. I'm addicted to it, I admit."