No, she doesn't wear a dark suit and darker glasses, and yes, she still has her fingerprints. But that doesn't change the fact that Cassie Conley, NASA's planetary protection officer, is in charge of protecting Earth from alien invasions.

Actually, that's only half her job, which is to ensure that outgoing missions to places that might be capable of harboring life don't get contaminated with Earth microbes, and to ensure that any missions to far-off places don't bring back the real-life version of the Andromeda strain. Or, as Conley puts it, "Don't throw your garbage on somebody else's lawn, and don't bring something unfortunate home."

To succeed at this, Conley must know what kinds of organisms can survive space travel as well as what the absence of gravity, not to mention space radiation, might do to the organisms. She must figure out how best to sterilize spacefaring instruments; baking them, as NASA used to do, isn't a good option for the sensitive electronic components on modern spacecraft. And she must do it all with diplomacy because saying, " 'If you don't do it right, you can't launch,' isn't an effective way of encouraging people to do what they need to do."

At this point in history -- with moon landings in the distant past, the space shuttle recently retired, and manned missions to Mars decades off -- these may seem like mere theoretical concerns. But Conley says the issues are, in fact, urgent. Understanding how earthly bacteria behave in space will be crucial for diagnosing an astronaut with the sniffles on the way back from a Mars mission and those studies may take years. "If we can't figure out what made them sick and prove it's an Earth organism to everybody's satisfaction, ... it's unlikely that the 8 billion people on Earth are all going to be willing to have that come back to Earth." It could be a common rhinovirus, or it could be a completely new organism.

Outward contamination is a risk every time NASA launches a robotic probe toward Mars, and the next such launch -- the Mars Science Laboratory, a.k.a. "Curiosity" -- is scheduled later this month. If bacteria brought from Earth colonize Mars, science missions seeking martian life would be jeopardized. Worse, our bacteria could kill off any life already there.

Planetary protection isn’t just a good idea: it’s a mandate. The Outer Space Treaty, which the United States signed in 1967, requires that the exploration of the moon and other “celestial bodies” be conducted “so as to avoid their harmful contamination and also adverse changes in the environment of Earth resulting from the introduction of extraterrestrial matter.” Now that we know the moon is unlikely to harbor life, moon missions are held to a less stringent standard than trips to Mars, Europa, or Enceladus, but even moon shots require some basic planetary protection actions.

Planetary protection is, not surprisingly, a cross-disciplinary field. Conley's background is in biology, physics, and Russian and French translation (among other subjects). John Rummel, her predecessor, is now head of a coastal science institute at East Carolina University in Greenville.

Surrounded by science

Conley's mother was a geneticist studying fruit flies and her father, a mathematician, helped develop the orbital mechanics calculations that drove the Apollo program. In middle school, Conley conducted experiments on a tarantula. "I would feed it crickets and see how much it weighed, ... try to make it fat," she says. High school was lapidary club, fencing, and "science and math as high as they went." She thought about working for NASA like her father, even going so far as to design a fruit-fly experiment for the space shuttle's Get-Away Special program, which allowed schools, clubs, and professional societies to design small experiments to be flown to space. But her experiment "didn't go very far” in the selection process, and never flew.

After flirting with physics as a major at the Massachusetts Institute of Technology (MIT), she ended up double majoring in biology and humanities with a minor in music performance. "That was just sort of the thing you did at MIT," she explains. "You did what you felt like," even if it meant taking seven classes a semester.

After graduation, Conley moved to Cornell University to study plant science. Biology, she says, had always been her main interest, and after a botany elective at MIT her senior year she decided to focus on plants. "Plants don't scream when you cut pieces off them, so in terms of doing the kind of biology I was doing, it was much more pleasant to be doing that to organisms that liked having pieces cut off."

She wrote her dissertation on pollen sterility in petunias, but she also studied cell structure, which led her back to animals and a postdoc at the Scripps Research Institute in San Diego, California, where she studied a protein on the ends of actin filaments. "I wanted to study that function in animals and then go back and study it in plants," she says. It turned out that plants didn't share that protein, but she did manage to demonstrate that disrupting the protein’s growth causes muscles to atrophy in rats, rabbits, and fetal chicks.

Then she took a risk.

"I was looking at the Pathfinder Web site for the rover, which was on Mars at the time, and I thought, 'Whoa, space. I could apply. Maybe I could work for NASA after all.'

"So I sent an e-mail to the responsible official at the bottom of the Web site, saying 'What would be needed to work at NASA?' ” That contact forwarded her résumé around NASA, and within a day, she received “scads” of responses from NASA researchers offering postdoctoral positions. “Well, I didn't want to do another postdoc," she said, so she didn't apply. However, a few months later, through this same e-mail contact, she learned of an open job at Ames Research Center at Moffett Field in California.

"We had 50 really good applicants" for the position, says Emily Morey-Holton, Ames branch chief in gravitational research, who ended up hiring Conley. "Her whole background was unique."

Conley started a research lab to study muscle atrophy in space. In one of her experiments she studied gene expression in nematodes subjected to 15-G pressures, using Ames's human centrifuge. "So all these people who had worked on the system in the '60s and '70s came in to get the centrifuge up and running, and then all the people who were working in the building where the centrifuge was stayed home for 4 days because it vibrated the entire building," Conley says. Soon, Conley secured a spot for her nematodes on STS-107, aboard the Space Shuttle Columbia.

"The launch was gorgeous. It was one of the most beautiful launches; everyone was saying so. It was the first one I'd seen, so of course it was gorgeous to me." That night, she went out to dinner and found a pearl in her oyster: "That's how lucky that day was."

But the mission's luck ran out on 1 February 2003, when Columbia broke up during re-entry. It was one of NASA's worst-ever disasters.

Weeks later, officials recovered the canisters that contained Conley's nematode experiments. Months after that, Conley's team opened the cans and found still-living worms.

It was an important result. It meant that complex organisms could survive a catastrophic crash to Earth that was in many ways similar to a meteorite impact.

Clean rooms, clean planets

Conley left Ames and wound up at NASA headquarters in Washington, D.C., invited by Rummel, who was then the planetary protection officer. "What I didn't know at the time," Conley says, "is the way the position is turned over: The current planetary protection officer finds somebody who's willing to come, brings them in, and then leaves. You catch somebody who doesn't know how to say no." Conley is joking, but Rummel confirms that when he first got the position, he thought he was going to be working on life support systems until the person who'd hired him left a week later, leaving him in charge of astrobiology and planetary protection.

Conley was appointed planetary protection officer in 2006. It's a job that uses her whole background, from biology to engineering to physics. Morey-Holton, Conley's supervisor at Ames, isn't surprised that Conley found a multidisciplinary job. "It's really refreshing to find someone who realizes the complexity of biological systems. ... It's always driven me crazy that people who study muscle don't study bone and people who study bone don't study muscle," she says. "I think she's somebody ... who would be bored by trying to focus on a single thing."

But the aspect of her training that has proved most useful, Conley says, is her training in translation at MIT. "In terms of a biologist talking to engineers ... [I have to] make sure they understand what I mean and I understand what they mean."

While the planetary protection office is currently an office of one, Conley expects the field to expand. With private companies like Virgin Galactic promising to take tourists to Mars and the nonprofit Planetary Society hoping to send microbes to orbit the Mars moon Phobos (though as of this writing the probe is stuck in Earth's orbit), "these issues are becoming more and more obvious. ... It is very clear that in order to accomplish everything that needs to be accomplished there will need to be an office of larger than one."

So get out your black suits and dark shades. Planet Earth's future is on the line.

Rachel Kaufman is a freelance science writer living in Washington, D.C.

Rachel Kaufman is a freelance writer living in Washington, D.C.