NASA scientist guards the planet from dangerous stowaways on space flights.
Among the many impressive government power titles-admiral, ambassador, Cabinet secretary-the weightiest of all might belong to an unassuming NASA scientist. As planetary protection officer, Catharine Conley has the awesome responsibility of shielding planet Earth from an alien invasion.
The invaders Conley worries about are not the vicious extraterrestrial beasts depicted on the silver screen in Independence Day or War of the Worlds. Rather, they are dangerous microorganisms brought back to Earth on a spacecraft, like the ones in the 1971 movie The Andromeda Strain.
Some might call Conley's role as planetary guardian an unusual extension of her wide-ranging research on proteins involved in muscle contraction and muscle function in extreme environments. Six years ago, while at NASA's Ames Research Center in California, the plant biologist had an experiment on the shuttle Columbia's ill-fated mission. In her experiment, Conley studied how microgravity affects tiny worms called nematodes. Despite Columbia's catastrophic explosion upon re-entering Earth's atmosphere, five of six canisters from the experiment were retrieved intact, and most still had live nematodes inside. The nematodes' survival gave weight to a hypothesis known as panspermia, asserting life on Earth could have originated elsewhere in the solar system and arrived on the planet as a passenger on an asteroid.
After NASA's incumbent planetary protection officer, John Rummel, prodded Conley to consider the implications of her experiment's results, she started to think more broadly about life forms beyond Earth. When Rummel moved on and recruited Conley for his job, he jokingly handed over a pair of sunglasses to signify the fearless feds in the movie Men in Black, entrusted to save Earth from marauding aliens.
NASA's missions must "follow the  Outer Space Treaty, which specifies that when we go to explore other planets we shouldn't cause any contamination that would interfere with future activities, and that when we are going to bring back things from other places, we should not cause harmful contamination to the Earth," says Conley, who is working with the international Committee on Space Research to develop safety precautions. She also consults with colleagues from the Agriculture, Energy and Homeland Security departments, the Centers for Disease Control and Prevention, and the U.S. Geological Survey. When a NASA mission involves bringing a soil sample from Mars, for example, Conley expects the DHS Customs and Border Protection directorate to be involved.
Protecting Earth from potential extraterrestrial pathogens became a priority 40 years ago when American astronauts landed on the moon. As a precaution, the Apollo 11, 12 and 14 lunar exploration crews were quarantined upon their splashdowns in the Pacific Ocean. Some at NASA didn't think it was necessary to isolate astronauts, considering the moon's temperature extremes, harsh radiation and lack of life support, but the National Academy of Sciences was more cautious. Dr. Charles Berry, the Apollo astronauts' physician, sat in a meeting when President Lyndon Johnson approved the quarantine, remarking that he did not want to be held responsible "for bringing lunar plague back to the Earth." But history proved NASA correct, at least about the moon's equatorial regions.
Conley sees no need for quarantines when NASA starts sending crews to lunar polar areas around 2020. "The Earth and the moon are basically one system," she says. "For a long time, material has been transferred back and forth between the Earth and moon. . . . We do not anticipate that there ever would have been or could be now life on the moon, and therefore it is extremely unlikely that there would be any biological hazard from which we would need to protect the Earth."
Mars is a different story. Because it is the most Earthlike body in the solar system, with a thin atmosphere and relatively warm temperatures, and evidence of water sources, many scientists see a credible possibility that if Martian microorganisms exist, they could be carried to Earth.
Conley says the planned Mars sample return mission, likely decades away, will require a biosafety containment facility, the "kind of facility you would have when you are studying the Ebola virus, or when you are studying smallpox."
According to Conley, Earth's natural history demonstrates the reasons for such precautions. "We know here on Earth we have done a significant amount of damage by transferring organisms from one place to another-rabbits being imported to Australia and Dutch elm disease in the U.S. being examples. Since we really have absolutely no idea what there might be on Mars, the precautionary principle dictates that if you don't know, you should take reasonable steps to make sure that you don't do something you aren't unaware of until after it happens, and you can't fix it," she says. "[We also] have to make sure the Mars samples don't get contaminated with Earth life."
As for the first human mission to Mars, any possible quarantine would be needed only to "keep the astronauts safe, because they wouldn't have been exposed to smallpox, and they wouldn't have been exposed to any new bacteria or viruses like swine flu," she says.
Conley does worry about one scenario discussed in The Andromeda Strain novel, in which a killer organism unleashed by a returning satellite had originated on Earth and mutated into a virulent form in space. "That's why we want any human missions [to Mars] to monitor the types of microbial populations that they have on the spacecraft," she says. These are the concerns of a scientist who never expected to have the weight of the world on her shoulders.
Edward Goldstein was lead writer at NASA from 2002 to 2009.