America's Best Leaders: Fiona Harrison & Maria Zuber, NASA scientists

The first two women to head their own NASA robotic space missions.

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Maria Zuber (left) and Fiona Harrison

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Maria Zuber noticed something strange on her first NASA mission. As a geophysicist in the 1980s, she was working on the science team designing the Mars Observer, an unmanned spacecraft that was supposed to be the first to study the geoscience and climate of Mars. "Somebody called me up," she recalls, "and said, 'Do you know on this mission there are 87 science investigators, and you're the only woman?'"

At first, Zuber, now a professor of geophysics at MIT, didn't believe it. She was aware, of course, that most of her colleagues on the mission were men, as they had been in graduate school and as they were in every physics department she'd been in. But she'd never realized just how few women had climbed with her to the top of the hard sciences and into the exclusive boys' club of NASA. "I said, 'No way,'" Zuber notes. "Then I started going through the list."

To Zuber's credit, as well as NASA's, she is not merely on the list anymore. She has climbed to the top of it, and she is not alone. Last winter, more than a decade after NASA lost contact with the Mars Observer—which disappeared in space in 1993 after a communications malfunction—Zuber became one of the first two women to be named the scientific leader of her own NASA robotic space mission. She shares the achievement with Fiona Harrison, a physics professor at the California Institute of Technology. "They were chosen because they are the best," says Alan Stern, a former NASA administrator who was on the selection committee that approved the missions proposed by the two women. "Space science is changing, and we now have a number of talented and experienced women scientists who are in a position to lead entire space missions."

Zuber and Harrison, who work on opposite sides of the country and rarely cross paths professionally, are leading two distinct missions for NASA, both set to launch in 2011. Zuber is heading up a group of scientists working on a $400 million project that will send two small orbiters into space to study the gravitational field of the moon. Data collected from the orbiters may shed light on how the terrestrial planets in the solar system were formed.

Harrison's mission, with a budget of $150 million, will send a high-powered telescope into orbit to observe the properties of black holes, the mysterious objects at the center of every large galaxy that are so dense even light can't escape from them. "It sounds like science fiction, but it's real," says Harrison, whose next-generation detection equipment is also being used by the Department of Homeland Security to test for radioactive materials. "We're in a very limited time in history where we can observe the cosmos and get detailed information about it—and actually do physics by studying these very extreme environments from space."

Green light. More than 25 years after Sally Ride became the first American woman to reach outer space, Zuber and Harrison are reaping the rewards of a renewed effort by NASA, still smarting from a series of high-profile stumbles on its flagship, multibillion-dollar missions, to make space exploration faster and cheaper and to allow more scientists to contribute. In the mid-1990s, the space agency began holding competitions for scientists interested in taking their work into space, awarding smaller amounts of funding—and, in Zuber's case, even a spare rocket—to a handful of astrophysicists and planetary scientists whose proposals promised to be both low cost and high impact.

When Zuber's and Harrison's missions were given the green light by NASA this winter, they took over teams of between 60 and 80 engineers, spacecraft contractors, NASA project managers, and fellow scientists—all of whom needed to be pointed in the right direction at the same time on tight budgets.

The vast majority of their colleagues are still men, but some women have also joined Zuber and Harrison as they break through NASA's glass ceiling. "I think it's beginning to change," says Harrison, whose spacecraft and mechanical systems engineers are both women. "There are not a lot of role models, and it's a competitive field, but there's a lot of young talent out there."