Seeding the Universe

The search for life on Mars could be a bit complicated by the hitchhikers on our rovers.

By Alan Burdick|Friday, October 01, 2004
RELATED TAGS: EXTRATERRESTRIAL LIFE, MARS

The search for extraterrestrial life begins, and perhaps ends, in a white gymnasium-size room in the smoggy foothills of Pasadena, California, on the sprawling campus of NASA’s Jet Propulsion Laboratory. This is the Spacecraft Assembly Facility (SAF), where interplanetary probes are assembled and tested before being launched toward their various cosmic destinations. The Mars Pathfinder rover, which in 1997 captured

stunning photographic vistas of the Martian surface, was built here. Spirit and Opportunity, the two rovers that continue to roam and prod Mars for evidence of water, were built here. Cassini, now orbiting Saturn, and Huygens, a small probe that in December will drop into the atmosphere of Saturn’s moon Titan, were built here too. The Spacecraft Assembly Facility is a gateway, truly a portal to the rest of the universe. What passes through it promises to reveal a great deal about the origins, and possible fate, of life in the cosmos.

Come on in. First, however, you must be decontaminated. A visitor places one foot, then the other, into an automatic shoe scrubber, a box on the floor with spinning bristles that flagellate the soles for a minute or so. A guide provides blue paper booties to slip over shoes, a blue shower cap to cover hair, and a white gown, made of paper with a shiny cling-free coating, to wear over your clothing. Finally, an air shower—a glass booth with several nozzles blowing furiously. Then and only then, ruffled but purified, may you enter. Inside the facility, a company of blue-bootied, shower-capped, paper-gowned technicians fuss over the skeletons of spacecraft-to-be. The room is arid as a desert, the humidity a drastically low 42 percent. The floors are regularly scrubbed to remove dander and bacteria. NASA’s intent is to create an environment hostile to any microbes that might hitch a ride aboard the outbound spacecraft yet benign to the human engineers who must assemble these delicate vehicles. If that sounds like an impossibility, it is. Welcome to the paradox of planetary protection.

In 1967, inspired by a new international outer-space treaty, the space-racing nations of the world agreed to spare no effort in preventing the potential spread of organisms from one moon or planet to another. At NASA, this mandate evolved into an official planetary protection policy, a Sisyphean effort to shield the universe from the people exploring it.

Traditionally, the assumed beneficiary of planetary protection has been the planet Earth. We’ve all seen the movies, we know the disaster scenarios: Extraterrestrial spores return from outer space, and in no time the citizens of Earth are heaps of dust or brain-dead zombies. Accordingly, NASA has developed an elaborate quarantine protocol to handle soil samples retrieved from other planets—comforting, perhaps, but statistically of marginal value. Contagion spreads from the haves to the have-nots, and so far as scientists have yet determined, Earth is the only planet with life to give. Besides, virtually all the spacecraft that leave Earth depart on one-way missions: They drift eternally through interstellar space, or they burn up in foreign atmospheres, or they sit on Mars, never rusting, transmitting data until their batteries fade away. Among all the lawns in the cosmos, ours is the one with dandelions, and the wind is blowing outward.

No, if anybody should be worried about biocontamination, it’s our planetary neighbors. In the coming decade, NASA has scheduled no less than four major missions to Mars to grope for hints of water or life. Down the road is a robot that will drill below the icy surface of the Jovian moon Europa to probe a briny ocean believed to exist there, and the Titan Biological Explorer, which will plumb the atmosphere of the Saturnian moon Titan for the chemical precursors of life. Interplanetary traffic is picking up, and NASA would like to avoid going down in history as the agency that accidentally turned the Red Planet green with life.

But the true worry isn’t ecological; it’s epistemological. Any earthly contamination—of the Martian soil or of the instruments sent to study it—would seriously muddy the multibillion-dollar hunt for extraterrestrial life. As Kenneth Nealson, a University of Southern California geobiologist and Jet Propulsion Laboratory visiting scientist, recently told the journal Nature: “The field is haunted by thinking you’ve detected life on Mars and finding that it’s Escherichia coli from Pasadena.” As it turns out, that fear is well founded. Not only does microbial life survive in the Spacecraft Assembly Facility; in some cases it thrives there. There is no question whether we’re exporting life into the cosmos—we absolutely are. What’s left to determine is exactly what kind of life is emigrating and how far it is spreading.

“Bugs are very clever,” Kasthuri Venkateswaran says with affection. “They started out on Earth 3.8 billion years ago, when nothing else was here!”

Venkateswaran—bow tie, oxford shirt, smart round glasses—occupies a bunker-like office a couple hundred yards up the hill from the Spacecraft Assembly Facility. Unofficially, he is an astrobiologist, a job description recently coined at NASA to describe the cadre of scientists involved in the agency’s accelerating search for life beyond Earth. Officially, he is the senior staff scientist of the biotechnology and planetary protection group. While his celebrated colleagues design ever more inventive spaceships and robots to scour the surface of Mars for some signature of life, Venkateswaran quietly examines the machinery itself, searching for any clever microbes—“bugs,” he calls them—that might try to tag along. Neat and kindly as country doctor, he is in fact the biological protector of the universe. To colleagues and, at his insistence, visitors, he is simply “Venkat.”

“The life-detection techniques we have today are incredibly sensitive,” Venkat says. “A few molecules could jeopardize the sample you’re bringing back.” He pulls out an official pamphlet: Biological Contamination of Mars, Issues and Recommendations. The surfaces of outbound NASA spacecraft and instruments, it declares, should be rid of living stuff, dead stuff, parts of dead stuff, and any stuff that might be mistaken for any of these. And everything in this effort is always being rethought. Recently, NASA stopped using cotton swabs in the cleaning process: To a life-detection instrument, the atomic bonds in a stray filament of cotton could be mistaken for the signature of proteins. The last thing Mars scientists want to discover is that Martians are the evolutionary descendants of Q-Tips.

In the old days, ridding the average spacecraft of bugs was a simple matter: Place it in an oven, heat it up to a jillion degrees or so, and bake it for a couple of days. Today, spacecraft are far more sophisticated and fragile, made of lightweight polysyllabic polymers and stuffed with microcircuits and light-years-beyond-Microsoft software.

“Nowadays, most electronics can’t take that kind of heat,” Venkat says. Instead, the individual components of the spacecraft are swabbed down with alcohol during construction; the components that can take it also undergo some sort of heat treatment. (The swab approach is by no means bugproof. Venkat has found that the alcohol sometimes breaks apart microbes and glues their innards to the spacecraft; this kills the microbe but leaves the prospect of life-detection even muddier than before.) The various parts of a given spacecraft are built, and decontaminated, by subcontractors around the globe. NASA readily concedes that it is physically—or at least financially—impossible to remove every speck. Instead, the agency issues guidelines intended to minimize the risk of contamination: no more than 300 specks per square meter, say, for a landing pod actively involved in the life-detection process. The components are then sent to the Jet Propulsion Laboratory or another NASA campus for inspection and final assembly. This is where Venkat’s research begins in earnest.

I toured the Spacecraft Assembly Facility with Victor Mora and Jesse Gomez, two of the space-age custodians responsible for keeping the place tidy. Spacecraft parts that come into the room are relatively free of microbes to begin with, they said. All that’s required is to keep the density of free-floating particles to a minimum. Dust, hair, the sloughed-off skin cells of NASA workers—all are contaminants in their own right and, more important, nutritious meals for whatever microbes might be around. “We’re shedding all the time,” Mora said. “Even our eyes shed.” Giant fans in the ceiling, several dozen feet overhead, suck particulates upward and outward into exile. The antistatic robes worn by technicians funnel personal particles down toward the floor, which is swabbed regularly.

“Microbes need particles to attach to,” Venkat says. “Without particles, without nutrients, the environment is essentially extreme.”

If astrobiologists have learned anything, however, it’s that almost no environment is too extreme for life. In the past few years, scads of extremophile organisms have been discovered thriving under conditions once considered inhospitable. Clams have turned up in the sunless, high-pressure depths surrounding seafloor vents. Algae in the Antarctic, where conditions resemble the dry valleys of Mars, spend much of their lives desiccated and drifting in the wind, waiting for their situation to improve. Microbes have been found miles underground in hot geysers, in gold mines, in solid volcanic rock, deriving their nourishment from sulfur, manganese, iron, petroleum. In recent years, a whole new field called geo-microbiology has sprung up precisely to study tiny creatures that are otherwise indistinguishable from rocks. Astrobiologists agree that if there is life to be found beyond Earth, it almost certainly will be very small and equally hard to discern.

Trained as a microbiologist, Venkat brings to his task an impressive history of sleuthing out wily tiny critters. In 1998 he discovered a bacterium that survives the high salinity of Mono Lake in California by living inside the lake’s rocks. After prominent newscasters and government officials were mailed anthrax spores in the autumn of 2001, Venkat published a paper later used by the Department of Homeland Security on how to distinguish anthrax from other microbes. None of his encounters in the microworld, however, quite prepared him for the discoveries he has made in Pasadena. Using a sophisticated array of life-detection methods—the same methods being refined for the hunt for extraterrestrial life—Venkat has discovered a plethora of bizarre microbes thriving in the Spacecraft Assembly Facility, microbes that would have escaped detection by older technologies. He held up a red-capped vial for me to see. Inside, invisible in a thimble-size sea of clear liquid, were the newly found inhabitants of Planet NASA. Venkat’s lab encompasses a true microcosm: a new world, hitherto unexplored, as enlightening as any that his stargazing colleagues will ever hope to find.

Thus far, Venkat has identified 22 species of microbes in the Spacecraft Assembly Facility, in other, similar NASA environments, even on actual spacecraft. Many are microorganisms common to arid environments, such as B. mojavensis, a bacterium that probably drifted in from the Mojave Desert. A handful are entirely new species. One, which Venkat has named B. nealsonii (in honor of Kenneth Nealson, who was his supervisor at the Jet Propulsion Laboratory), possesses two protective coats, making it a tough spore capable of surviving in the ultradry environment of the assembly facility. As Venkat discovered, the second spore coating also offers a secondary benefit: It makes the organism unusually resistant to gamma rays, a form of cosmic radiation that, in large doses, is fatal to men and microbes alike. (Earth’s atmosphere screens out most gamma radiation; Mars, in contrast, is a gamma-ray frying pan.) Tough as it is, the bacterium is probably not unique to NASA. The world of undiscovered microbes is vast, and Venkat suspects that B. nealsonii also resides outside the assembly facility.

Venkat has found bugs in the spacecraft-assembly facility at the Kennedy Space Center in Florida; on hardware and in drinking water from the International Space Station; in circuit boards destined for an upcoming mission to Europa; and on the metal surface of the Mars Odyssey spacecraft, which has been orbiting Mars since October 2001. While Odyssey was being assembled at the Kennedy Space Center, Venkat isolated a new species of bacterium—Bacillus odysseyi, officially—that carries an extra spore layer, or exosporium, that makes it several times more resistant to radiation than other spore-forming microbes found in the facility. “It carries novel proteins as a sunscreen,” Venkat says. Like B. nealsonii, B. odysseyi may turn out to live elsewhere besides its assembly facility. But what’s notable, Venkat says, is that the very traits that render these bugs impervious to decontamination also grant them a decent chance of surviving the radiation shower they would encounter en route to and on the surface of a place like Mars.

One discovery, a bacterium named Bacillus pumilis, has given Venkat particular cause to marvel. He found the microbe thriving directly on spacecraft surfaces, presumably drawing its energy from ions of trace metals like aluminum and titanium. “Aluminum is toxic,” Venkat exclaims, baffled. “There are no nutrients. There is no water.” In addition, the species exhibits a remarkable defense against desiccation. The individual cells form protective spores, which then band together to create what Venkat calls an igloo. In microphotographs, this spore house looks rather like a macaroon. Moreover, when Venkat cuts open the igloo, he finds no visible trace of the individual spores; they’ve all dissolved into the collective matrix. High-tech methods of life-detection reveal no evidence of life. Yet when Venkat warms up the igloo and adds a little moisture, B. pumilis again springs into being. If the microbe is any indication of the sort of life that awaits discovery on Mars or elsewhere, he says, good luck to the robot sent to detect it.

B. pumilis itself isn’t a new species. It has been studied throughout the world for years, but its igloo-forming habits were not well known. For instance, its attachment to aluminum is novel. Last month, Venkat published a paper claiming that the SAF version of B. pumilis is in fact a new species after all—a substrain that has adapted and evolved to the conditions imposed on it by NASA, like an herbicide-resistant dandelion or the supertough microbes that sometimes spring up in hospitals. He has named it Bacillus safensis, and it represents precisely the kind of organism that his fellow astrobiologists are looking for in outer space. It’s not a Martian, but in form and function it may turn out to closely resemble one.

It is, in any event, one step closer than any other earthly creature to becoming the first organism to survive on another planet. Venkat has found the bacterium in every other NASA assembly facility he’s studied. Three years ago he found it on the Mars rovers Spirit and Opportunity, then under assembly at the Jet Propulsion Laboratory. At this very moment, the rovers are actively poking around in the Martian dirt, as they have been for the past nine months. B. safensis is almost certainly aboard them, alive and well, Venkat says. “They could be there for millions of years because they are spores. Whether they will become active and begin terraforming—that research is still ongoing.”

The Space Assembly Facility is a standing paradox. Through its assiduous effort to avoid spreading life throughout the cosmos, NASA has created an environment that inadvertently fosters the very kind of life it is traveling so far beyond Earth to find. As Venkat says, “We have a kind of survival of fitness.” What began as a means to an end is now an end in itself; the doorstep has become a laboratory, a nursery even, a small-town study in life’s cosmic persistence. It is a study, too, in the impossibly high cost of perfect hygiene. Venkat found that, in at least one instance, some of the microbes appeared to have been introduced during the cleaning process devised to eliminate them. Wherever humans go, it seems, we go with company. Looking around the assembly facility with Mora and Gomez, I saw a man-made cosmos, every surface a habitable planet, its ethers traversed by micronauts riding spacecraft named Human Hair and Eyeball Cell.

“People are the dirtiest things around,” Gomez said.

“Yeah,” said Mora. “We’re the contaminants.”

ANYBODY OUT THERE?

As NASA’s search for extraterrestrial life advances, it more and more resembles a trip through a hall of mirrors. The farther from Earth our gaze wanders, the more our very presence seems to nag us. Can we search for foreign life without contaminating it with our own? Can we discern the contamination from the real thing? If ultimately we’re related, if we’re all evolutionarily relatives from way back, is there even a difference? Some scientists wonder whether logic will permit us to find anything but ourselves out there: Our understanding of what constitutes life is shaded by what we know on Earth, so that’s all we know how to look for. It’s like that old joke about the guy who hunts for his keys under the lamppost because that’s where the light is. In his office, NASA microbiologist Kasthuri Venkateswaran—known as Venkat—nods vigorously in affirmation.

“Maybe it’s something you’re not able to detect with the naked eye. Maybe it exists on a different wavelength,” he says. A public-relations minder from NASA looks less than thrilled by Venkat’s speculations. He goes on: “You might think I’m crazy. Maybe there’s somebody walking around right now that we can’t see.”

The hunt for extraterrestrial life marks the ultimate test of humankind’s self-knowledge. We cannot find and recognize “other” until we can first, at the most basic cellular level, recognize “us.” Therein lies the true value of Venkat’s microbes. Having found B. nealsonii, B. safensis, and their kin—having in some sense fostered their creation and survival—NASA has no plans to destroy them all. On the contrary, Venkat intends to keep them alive as a sort of microbial archive for future reference. Someday, maybe soon, scientists will flip over a rock on Mars or Europa or somewhere out there and claim the profound, the first-ever discovery of “them.” How to tell for certain? We will hold up a mirror and compare appearances; that mirror awaits in Venkat’s office. His microbes are us: our emissaries, our representatives, the reflection of our wily selves. Deciphering and confirming the distinction—them or us—will most likely take years. But as Venkat sees it, those are precisely the hard facts that humans evolved to tease apart.

“It’s tough,” he says. “But that’s where our intelligence comes in.”          

— A. B.

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