Four years ago, NASA was rushing at Mars with no less than a dozen missions. A primary objective was to bring samples of Martian soil to Earth by 2008. But late in 1999, the Mars Climate Orbiter disappeared, followed 71 days later by the Mars Polar Lander. Getting rocks back from the Red Planet was postponed until at least 2014, and that was a source of both disappointment and relief to Carlton Allen.
Allen is NASA's curator of astromaterials at the Johnson Space Center in Houston. On the one hand, he's dying to get hold of some Mars rocks. On the other hand, he believes that Earth is not ready to receive anything from Mars that could harbor alien life-forms. His fears are based partly on new discoveries from places like Antarctica and the bottom of the Pacific Ocean that show small life-forms like bacteria have found ways to thrive in extreme places. He also worries because no one has a very good idea of just how we might seal off Martian rocks from the rest of us.
At the same time, scientists face the challenge of keeping Earth and its many life-forms from contaminating whatever we bring back from Mars. As NASA's planetary protection officer John Rummel puts it, you don't want to declare you've found a Martian microbe "when all you've found is life from Florida or Texas." That means a successful containment lab must combine biosafety technology developed for germ warfare with clean-room technology developed for computer chips. "We have not demonstrated that we can integrate those functions to meet planetary protection requirements," Allen says bluntly.
Two hundred miles west of Houston, in San Antonio, Scott Shearrer lays his big blue space suit down on the gray floor. The suit is designed for dangerous inner space, not outer space. Shearrer, an affable Texan with a trim moustache, a passion for barbecue, and a ready smile, checks for tiny rips in the fabric. Finally satisfied that the suit is airtight, he pulls it over his legs and puts on a radio headset.
"Radio check, Jack."
"Roger, Scott, loud and clear."
Shearrer pulls on the suit's left arm, the headpiece, and then, with a practiced contortion, the right arm. He zips the diagonal closure across his chest and attaches a yellow air-supply hose to a hip port.
Jack Kelley sips tea in his office and monitors Shearrer's progress via radio. He is the director of the environment, health, and safety department at the Southwest Foundation for Biomedical Research in San Antonio. Shearrer is his right-hand man in charge of maintaining the lab, the newest of just six biosafety level-four labs in the United States and the only private one. Federal-government-run labs include one at the Centers for Disease Control in Atlanta and one at the United States Army Research Institute of Infectious Diseases in Maryland, a biological-warfare research center.
"I'm entering now, Jack."
"Roger, standing by."
Shearrer waits before a thick steel door with inflatable rubber seals that leads to a shower room, which serves as the antechamber to the lab. He pulls down a handle on the door, the seals deflate, and air flows into the shower room, which is kept at a lower pressure than the suit-up room. He enters the shower room and waits while the outer door reseals. He faces the inner door and deflates its seals. Again air flows in silently. Then Shearrer enters the hot zone.
If you ignore the man in the blue space suit, the hot zone is just a room with sinks, countertops, freezers, and microscopes. To the naked eye, it's as unimposing as a college biology lab. But labs like these are defined by how dangerous they are. A level-one lab contains relatively innocuous microbes, such as soil bacteria. A level-two lab is used to research microbes that are not normally airborne, such as those that cause hepatitis B, polio, and measles. A level-three lab is designed to contain potentially lethal airborne pathogens for which a cure is available, such as tuberculosis. Level four is for horror pathogens that can't possibly be seen with a naked eye but are lethal, incurable, and spread by air or blood-to-blood contact.
Take, for example, Guanarito, the virus that causes Venezuelan hemorrhagic fever. Virologist Rebeca Rico-Hesse has been studying it here at Southwest's lab. If Guanarito is not properly contained, Rico-Hesse and her colleagues will quickly develop headache, fever, joint pain, skin rash, nausea, and diarrhea. Before long they will bleed into their intestinal tracts, vomit, and defecate black digested blood. Within 10 days they could die from organ failure. "It's sort of 'all systems down,'" says Rico-Hesse.
After a routine maintenance check, Shearrer returns to the shower room. His suit could be crawling with any of several dozen nasty bugs that scientists study in this lab, so for a full five minutes he is blasted with Lysol. Once back in his khakis and polo shirt, it's off to Rudy's Barbecue—"the best barbecue on the planet"— with Jack Kelley.
Over creamed corn and brisket, Kelley tells how he encouraged the architects and engineers who built Southwest's lab to "think like a microbe." They designed a place where viruses can't get out the door, because the air always flows inward. They can't ride out on space suits, because the suits are sprayed with Lysol. They can't get through the air system, because of high-efficiency particulate air filters. They can't get out through the drains, because anything that does is combined with disinfectant and then cooked at 250 degrees Fahrenheit for two hours. The lab is an isolated concrete box that has only 18 points of penetration for air, pipes, electric conduits, and people. Each opening is sealed. Inspection companies annually test the concrete for cracks, then repair it.
Carlton Allen has been tapping into the expertise Kelley obtained from building and overseeing Southwest's lab. Kelley says he doesn't know whether there's any life on Mars to worry about, but he appreciates Allen's concerns. "What if I'm wrong?" he asks, pouring barbecue sauce. "In this business, you don't plan for what you think. You plan for the maximum credible event. And the maximum credible event here is that we bring back a bug that's resistant to everything and anything we've got. And it's a major hazard to the biosphere.
"So," he concludes, with rare gravity, "that facility has got to be the best we've ever built."
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Modern containment technology was born at Fort Detrick, Maryland, during World War II, in response to fears that Axis powers might use biological and chemical weapons. President Nixon officially closed the offensive part of the program in 1972, but since then scientists have labored to develop vaccines to defend troops and civilians against deadly pathogens.
"We were dealing there with highly infectious agents and lots of them," says Manuel Barbieto, a veteran of the program, whose job was to test and improve the containment systems. "Every time we had an accident [someone got infected], we would investigate how it happened and what we could do to correct the problem." Tests were run on the lab building to determine what kind of paint works best (epoxy), how to dispose of wastewater (cook it until everything in it is dead), and what the ideal material is for purifying the air (high-efficiency particulate air filters). They studied seals and air locks, disinfectants and lab tools.
Perhaps the most important contribution by the researchers at Fort Detrick is the insistence that rooms in level-three and level-four labs, which contain lethal agents, must be at negative pressure compared with the outside, so that if there's a breach, air will flow in. Earth's viruses and bacteria cannot move from place to place actively. They must be carried around by air or fluid. They can't swim upstream. If air rushes into a lab through a crack, the microbes have no way of getting out.
The same principle of low-pressure airflow was also applied, in reverse, at labs that made guidance chips for missiles during World War II. In those labs, air flowed outward, keeping the atmosphere free of dust and bugs that could contaminate delicate assemblies. A Mars containment facility must be both at the same time.
Scientists have been trying for decades to figure out how they can protect space rocks from us and us from them. Only one idea has gained credibility: three concentric rooms. First, the rocks would be placed inside a sealed container filled with pressurized nitrogen, an inert gas that prevents chemical activity. Higher pressure inside would prevent anything else from getting in. Then the box would be placed inside a room with lower pressure. Finally, yet another room would be placed around the other two. It would have higher pressure than the surrounding outside air. Anything that escapes from the innermost box would go into the lower pressure area of the surrounding box and be taken through a complex filter system. Any contaminants from the middle box that drift toward the innermost box would be unable to penetrate it. The concept is a high-tech version of a castle moat. Any dirty, science-ruining Earth germs would be prevented from reaching the castle. And any nasty Martian bugs inside the castle would be stopped cold if they tried to escape.
"It's a slam dunk!" Kelley says. "It just has to be souped up and adapted."
Allen isn't so certain. He is concerned about the points where the moat is breached by doors and glove holes that allow scientists to examine the rocks. He'd like to have a second solution to compete against the concept. He is working on a prototype clean box with a built-in robot that can cut open and analyze the rocks so people aren't directly involved.
John Rummel says he intends to quarantine any rocks brought back from Mars until they are proved safe. But a 2001 National Research Council report says biologists already have difficulty detecting microbes in soil samples from Earth, so detecting something we've never encountered before strains the imagination. "By far the most likely outcome of the preliminary examination of the Mars samples," the report states, will be a resounding "Uncertain." And think of this: What if a Mars bug can eat through glass? What if it can swim up a pressurized stream of air?
Ultimately, the arguments and the models become absurd. So veteran virologist C. J. Peters, the Ebola-hunting hero of Richard Preston's The Hot Zone, suggests building a type of containment that would be balanced toward attempting to keep the rocks sterile: "You have to make a big leap to say there's life on Mars, and another big leap to say we can find it, and another big leap to assume that we can do anything about it if there is." Of course, if we can't detect Mars life, we won't know how to sterilize it either.
To a planetary protection officer entrusted with keeping deadly life-forms out of Earth's biosphere, doing nothing is the one option that is completely unacceptable. "Within any undertaking, there cannot be 100 percent assurance," Rummel says, "but avoiding unacceptable risks is what I do, and minimization of the chance of planetary contamination is simple prudence." With the best solution still not obvious, both Rummel and Allen remain content with a single thought: We have 12 years to figure it out.
Lessons From Apollo
The Apollo missions brought back a combined 842 pounds of lunar rock and soil between July 1969 and December 1972. If any moon bugs hitched a ride on those rocks— or on astronauts— they could easily have escaped into our environment. NASA's quarantine efforts failed, according to a National Research Council study on sample containment. The Lunar Receiving Lab was hurriedly built and underfunded. After completing the first moon landing in 1969, Apollo 11 splashed down in the Pacific, scattering lunar dust. Moreover, beginning with the Apollo 15 mission in 1971, NASA brass cut the astronauts' quarantine short for political reasons. "It was hard to take the rock quarantine seriously when these supposed vectors of disease were shaking hands in Houston supermarkets," says John Wood, the planetary scientist who chaired the Research Council study. In Wood's view, we're rather lucky that the moon appears not to harbor life.
A Box Within a Box Within a Box
The best proposal so far for containing life-forms within a soil sample from Mars is a system of three containment areas with varying pressures. The outermost area, or box, would be built like a computer-chip clean room with air at a slightly higher pressure than the outside atmospheric pressure. The area inside that box might be built like a biosafety level-four lab. It would have a lower air pressure than the room around it and filters that trap anything that leaks inward. The innermost box would contain the Mars soil sample and be pressurized with inert nitrogen kept at higher pressures than the surrounding box. A leak in the innermost box would cause nitrogen to rush out into the middle box. A leak in the outermost box also would cause air to rush outward, keeping earthly pathogens from entering and forcing any contamination toward the middle box, where it would be trapped.
