planetary_protection_000906 WASHINGTON -- It sounds like the stuff of science fiction.
A
robot spacecraft flies off to another planet, scoops up some soil and brings it back to Earth. Inside that scoop of dirt are living things that somehow escape, run amok and threaten our world.The scenario might sound outlandish until you consider this: For the first time since the 1960's Apollo
moon landings, the federal government is making plans to protect Earth from any extraterrestrial life forms brought back -- on purpose -- by scientific space missions. Highest stakes
The stakes could not be higher. Anything, from otherworldly contaminants to virulent microbes, are possible as NASA plans for missions that would retrieve bits of Mars and other cosmic bodies in the years ahead. The concern is that a harmful visitor from space might wind up endangering
Earth's environment or its inhabitants.
Closeup of test particles captured in a block of Aerogel, a wispy, glass foam, which is packed into the spacecraft Stardust's dust collector.
The first such sample-return mission is already on its way.
Stardust, which was launched early last year, is chasing icy Comet Wild 2, which is half a billion miles (805 million kilometers) from Earth. The probe is designed to gather particles from the comet's tail and bring them to Earth in 2006. The particles will be microscopic -- all of them could easily fit inside the period at the end of this sentence -- and probably won't contain any traces of life.But other missions could fetch pieces of
Mars or Jupiter's moon Europa, where life is more likely to be found. Other possible pickup points include Venus and the nucleus of a comet. In late 2002, the United States and Japan plan to launch a probe called Muses C to bring a chunk of an asteroid to Earth in 2007.Contain a strain
As elated as scientists might be to find evidence of life in any of those places, they plan to be careful to keep it contained. No one, after all, wants an "Andromeda Strain" on their hands.
"If there is a living organism in a sample returned from Mars, you don't want to let it out," said Margaret Race, a biologist at the
SETI Institute in Mountain View, California.~
"You don't have to look very far to come up with examples on Earth like the medfly, killer bee or gypsy moth to see that when you move a species from one place to another you can cause unintended problems, sometimes with significant impacts," she said.
No longer do space scientists have to worry just about "forward" contamination, that is, exporting Earthly bacteria into the solar system. Now, there's the danger of "back" contamination -- importing space bacteria to us. A 1967 international agreement, to which the United States is a signatory, establishes a requirement that spacefaring nations avoid contamination in either direction.
To that end, NASA is forming an internal "planetary-protection" committee of about 15 people to determine the care and handling of extraterrestrial samples. Assisting it will be another group with representatives from other federal agencies, including the departments of Health and Human Services; Agriculture; Interior; and Energy, as well as the Environmental Protection Agency (EPA) and the National Institutes of Health.
"Unconstrained experiments is not what we're about so we're going to be conservative," said John Rummel, NASA's chief planetary protection officer.
"If there is a living organism in a sample returned from Mars, you don'twant to let it out."
The National Research Council (NRC) two years ago ranked various objects in the solar system on their potential for life and issued recommendations on how to handle material from them. That July 1998 report followed a study by the NRC a year early on recommendations for NASA's proposed Mars sample-return mission, which has since been put on hold.
"The central concernis the possibility that samples returned to Earth from small solar bodies might harbor living entities that could harm terrestrial living organisms or disrupt their ecosystems," the report said.
Where life may live
At the top of the NRC list -- where the chances for life are greatest and thus "strict containment and handling are warranted" -- are Mars, Jupiter's moons Europa and
Ganymede and certain types of asteroids.Scientists doubt that meat-munching bugs or anything harmful to humans might exist in those places since there would be no such food source there.
"Being a human pathogen on Mars right now is not a very good business to be in," Rummel said. "You might find something that gobbles hydrogenbut it wouldn't pose a threat to humans."
At the bottom of the NRC list, where there is little or no chance for life and only basic containment would be needed, are places like the moon and interplanetary dust particles. Still, no one is taking chances.
"Nobody is proposing that cometary samples be brought back willy-nilly or handed around to kids in the neighborhood," Rummel said. "These samples are going to be handled very carefully."
Space dust and Martian fossils
The Earth, in fact, is bombarded with dust and rocks from comets and other bodies. Each year about 40,000 tons of space material falls onto land or in the ocean, scientists estimate. At least some of it is believed to have survived atmospheric entry without severe heating.
Already, there are bits of
Mars on Earth in the form of 15 confirmed meteorites, most of them found in remote places like the Sahara Desert or Antarctica. Perhaps the most famous of the Martian meteorites -- known as ALH 84001 -- set off a stir worldwide when a team of NASA scientists announced in August 1996 that the potato-shaped rock appeared to contain the fossilized remains of ancient Martian bacteria.But that and other meteorites got to Earth the hard way -- on their own, blazing through the atmosphere. Some are displayed in museums, others are in the hands of private collectors and a few are being studied in laboratories around the world.
By contrast, samples brought back by NASA's probes will arrive in their own sealed container at the end of a parachute to cushion the fall. Drop zones likely will be places like the Australian outback or Utah's Dugway Proving Ground, a military base where the U.S. Army tests biological and chemical defense systems.
There, NASA scientists can retrieve and examine the space samples under secure conditions before carting them off to a special "receiving laboratory." No facility yet exists to handle extraterrestrial material. The closest thing to it -- a biological containment lab set up at the Johnson Space Center (JSC) in Houston for the Apollo moon missions -- was dismantled after the program ended in 1972.
Locked down in a lab
Most of the 843 pounds (382 kilograms) of moon rocks remain locked down in a special lab at the center, bathed in nitrogen gas to prevent contamination by Earth bacteria. The new lab could be at any of three NASA centers -- JSC, Ames Research Center in Mountain View and the Jet Propulsion Laboratory in Pasadena, California -- that are involved in the planning for missions to return space samples. Or NASA might decide to locate it elsewhere.
Wherever the laboratory winds up, it probably will be modeled after lab standards at the Centers for Disease Control and Prevention in Atlanta, Georgia, which has four protection levels for scientists studying infectious Earth organisms.
Samples from Mars or
Europa would be handled under strict conditions similar to the highest protection protocol -- Level 4. At that level, researchers wear pressurized spacesuits and handle samples of fatal viruses such as Ebola in special safety cabinets."We have the technology for containment so that's not the issue," said Noreen Noonan, the EPA's assistant administrator for research and development who headed an advisory panel on planetary protection. "If you look at places like some government labs or military bases, they work with organisms that would scare the living daylights out of you if they ever got away."
Risk management
The bigger question, Noonan said, is "looking at risk from the standpoint of what are the likely scenarios? We have no evidence to suggest that things will actually come back on these missionsBut the whole idea of how to manage risk is very poorly understood, and the scientific community has not covered itself in glory in trying to explain it."
So far,
NASA is trying to adhere to the guidelines set by the National Research Council. The agency's planetary-protection committee is to meet next month to adopt a charter and set the framework for decisions governing future missions."This is one of those cases where the government's doing something right," said
SETI's Race, who is not connected with NASA but is working with the agency on the issue."They've been taking it very seriously," she said. "I'm comfortable in that if there were any reasons why we should not be [retrieving samples], then credible scientists should have stood up and said 'Hey, don't do this.' And they have not."
advertisement
