The Rock From Mars (30 page)

People had studied meteorites for a long time—for petrological, geochemical, and mineralogical purposes. Now, all of a sudden, there were organics from terrestrial life involved. As this project progressed, people in the meteorite game would show Steele images they had taken years earlier in which he clearly saw similar features. This phenomenon hadn’t been spotted earlier because those investigators were not trained in the subject.

In the past, the mere whisper of the word
contamination
meant the end of a meteorite’s career as a research subject for purposes of organic analysis. Once the rock was discarded, there would be no systematic follow-up research on
how
it had gotten contaminated. Other factors had to do with microscope viewing techniques and the random nature of microbial infestations.

Here was another instance in which artificial divisions in the academic and research worlds helped to create or prolong blind spots in human observations of nature. Such constraints could also explain why the painstaking efforts of Gibson and others in Building 31 to eliminate contamination from the rock had missed things. They had, for example, used only one kind of nutrient to try to culture the bugs. Steele knew you could give an organism the wrong thing to eat or too much to eat and that could yield a negative result even when there were bacteria present. What’s more, the Houston team had relied on colleagues who were
medical
microbiologists, not
environmental
microbiologists like Steele—who came in with a different set of assumptions and knew different ways of looking.

Steele’s approach to the rock covered different ground from that of the Zarelab team in their analysis of the organics (PAHs) in the rock. The Steele group was just tickling the surface, while Zarelab had been smacking much deeper holes in the material. Different techniques revealed different properties.

It was all about training the individual eye, Steele thought. In this case, David McKay had looked at the images and been unable to understand what he was seeing. But he understood that he didn’t understand. So he handed the puzzle to Steele—an
environmental
microbiologist.

As Steele would write in one of the numerous papers he and the team published on the topic, with David McKay among the coauthors, “In the particular case of ALH84001, terrestrial organisms went undetected by all the techniques that claim to be able to detect life.” There had been little impetus for research on this kind of contamination until the McKay group published its claims. It was then that “the issue of contamination from Antarctica came out of a backroom and was given serious thought, mostly by researchers seeking to discredit the work of McKay et al.”

Hardly a huge surprise in
hindsight,
Steele thought. The discovery mirrored everything people were learning about life’s robust nature.

The rock had been on Earth for 13,000 years, and on the surface of the ice (exposed to warming sunlight and snowmelt) for 500. Until about 15 years earlier, Antarctica had been regarded as a sterile wilderness. Among the factors that had allowed the microbes to escape detection, in Steele’s view, was general “ignorance of the diversity of Antarctic microbes,” which (scientists now knew) included bacteria, fungi, algae, cyanophyta, and lichens. As a survival strategy, Antarctic organisms were known to seek sanctuary inside rocks, which could contain liquid water from snowmelt, organics, and minerals they needed for growth.

The findings had implications for analyses done on other meteorites as well, since any contaminating organisms, eating away at the contents, digesting, and expelling material, could have muddied the picture for unwary researchers as to what was indigenous to the meteorite or its native home and what was terrestrial. These organisms needed stuff to eat; in other words, they weren’t primary producers themselves.

And therein lay the crux of a big problem, Steele knew. Which was basically that “you are what you eat.” So if you’re eating Martian organics, you take on that carbon-isotope signature. How do you tell which is which?

Steele and his colleagues turned up a wealth of microbial species not only in the Allan Hills meteorite but in other types of meteorites from Antarctica. In one type, they detected “living cells all through the core of the meteorites.” The shower of fragments known as the Murchison fall, which had landed in a farmyard and, by some accounts, in a manure-filled ditch, showed evidence of infestation by fungi and bacteria, Steele found. In some cases, he detected crystal growth that had occurred while the samples were in storage, growth that in certain cases might be mistaken for fossils.

And on a shelf in his lab, Steele was amused to see that, despite all precautions, old Chip, the speck of Allan Hills meteorite that had introduced him to his new career, was nourishing its own zoo of microbes. It was now carpeted with bacteria, right across its surface, and they were dining on and changing its minerals.

These revelations had profound implications for NASA’s planning for future Mars missions. Steele’s work, like other surprises flowing from the McKay group’s 1996 claims, raised particularly serious concerns for the ambitious plan to bring back bits of Mars for study in Earth labs.

Steele and company argued that meteorites got contaminated immediately upon contact with the terrestrial biosphere, at which time the microbes reprocessed any organic material the rock contained. And yet none of the traditional approaches used to refute the McKay team’s 1996 claims had detected anything alive inside the meteorite. Techniques that relied on electron microscopy and shape comparison, obviously, could take researchers only so far.

In pursuit of better tools, Steele got the idea of using biology’s natural survival techniques to probe for life signs, terrestrial and otherwise. In a word: antibodies. These are the soldiers of the body’s immune system—proteins that blood cells march out to repel invading bacteria or other foreign substances. The defense mechanism acts as a terrifically sensitive life-detection device. The little troops do their work by binding to a specific antigen (the invading molecule, fragment of protein, or whatever) like a handcuff around a wrist. Like so much in chemistry and therefore biology, this process depends on jigsaw shapes that fit together.

These techniques, called immunoassays, had become increasingly useful, as the technology advanced, in many areas of research—on everything from human health to ancient fossil biomarkers. For instance, antibodies could sometimes produce strong reactions in fossilized bone and bird-claw tissues. Antibodies had detected remnants of original proteins and other organic compounds in samples such as those of the dreaded
Tyrannosaurus rex,
dating back at least about 70 million years.

The important thing to Steele was this: research had demonstrated that the physical and chemical processes that follow the burial of an organism’s remains on Earth, leading to their preservation as fossils in rock, leave products that can be detected, even from as far back as the time when Mars had a more favorable climate for life.

Now Steele and his colleagues started adapting the technique to detect past or present life on another world, and also to provide details on the organisms’ metabolisms. There were a few little hurdles to be coped with, he noted, such as the fact that the technique was “Earthcentric” and might not work on weird extraterrestrials. In any case, the goal was an instrument called MASSE, a compact automated device that, they hoped, would fly on a Mars mission planned for 2009. His rallying cry, delivered at meetings where he described his project, would be: “Send your favorite antibody into space! Give us your blood!”

The tensions over the Mars rock were still on display at the next annual gathering of lunar and planetary specialists, in March 1998 in Houston. Naturally, the vitriol spilled into the social hours. One evening, the tourist attraction called Space Center Houston, next door to the real NASA space complex, was the site of a working cocktail party. Surrounded by Soviet space regalia, a partial mock-up of a space shuttle, and other exhibits in the giant hall, as many as a thousand people hoisted cold beers and dined on free cafeteria fare. Hundreds of posters—graphic displays of research results—were arrayed around the place, with the authors standing by to answer questions.

One of the schmoozers was John Kerridge, a cosmochemist and meteorite expert who was one of the most ardent McKay group critics. He remarked to a journalist that McKay and colleagues “have circled their wagons. They’re not really trying to find out what’s going on” with the evidence in the rock.

Not far away from Kerridge, a seething Kathie Thomas-Keprta walked up to David McKay with urgent news. According to an account in the book
Dark Life,
by Michael Ray Taylor, McKay’s face flushed and he turned on his heel and “stormed off” toward another section of posters a few yards away, where he accosted a meteorite expert named Derek Sears, from the University of Arkansas. “How could you even use this image?”

Sears and his coworkers had compared the wormy shapes reported by McKay et al. with forms detected in meteorites from the moon and pronounced them similar. Since the moon is considered incapable of sustaining life, and therefore the forms could not be fossil microbes, the Sears group had concluded that the proposed nanofossils in the Mars rock must also be nonbiological.

McKay found the images Sears used to illustrate the point outrageously misleading. “It is absolutely nontypical for a lunar meteorite,” McKay told Sears. An intern who had worked with both McKay and Sears had “spent months, hundreds of hours on the microscope, finding this one image,” McKay went on, his hand trembling as he pointed to the offending picture. “And it’s the only one she could find. This is just—just unconscionable.” And Sears had put next to it, for comparison, what McKay, among others, considered the least biological-looking of the images from the Mars rock.

“The pictures speak for themselves,” Sears responded. “If you were impartial, you’d see that.”

In the last years of the dying millennium, the divisions among scientists seemed to be hardening in place on the question of early Martians. People who looked favorably on the McKay group’s claims were outnumbered and overshadowed by many more who decidedly did not. In the broader world, there was a creeping sense that the claims had effectively been buried. That was the buzz, the conventional wisdom.

More laboratories had received their allocations of chips off the Mars rock, as $2.3 million in funds from NASA and the National Science Foundation fueled a spate of new studies. Many of the researchers had come up with findings that cast doubts on significant chunks of the McKay team’s hypothesis, and the McKay group gave ground on certain points:

•                  Some (though not all) of the wormlike microfossil shapes seemed to be bits of naturally formed clay or ridges of mineral.

•                  The rock was indeed loaded with Earth-born contaminants that apparently had seeped in with Antarctic meltwater.

The McKay regulars couldn’t help but be distracted, they had to admit, by the continuing rain of personal, and, they felt, often unfair feedback impuning their motives and their competence. In private moments, McKay sometimes found himself focusing furiously on one of his critics, his stomach knotting, instead of on the work, and that made him even angrier.

At some point, McKay came to suspect—ironically, in light of speculation that NASA had staged the whole affair to boost its budget—the stigma of “political incorrectness” had attached itself to his hypothesis. Some people seemed to believe that their prospects for funding could be jeopardized if they worked on it, or allowed the McKay group to use their facilities.

McKay group antagonist Ralph Harvey, who himself was fonder of confrontation than most, quipped that the McKay group “felt that they were being mistreated when in fact they were being treated with the same contempt any scientist feels during that period. . . . It’s contempt for anybody that would try and shake up the current paradigm.”

Still, no single finding managed to deliver a definitive knockout blow for either side. Each answer led to more questions. Factions developed within the “pro-life” camp and the “anti-life” camp. The antis, especially, seemed to fight among themselves as much as they argued against McKay.

And the McKay team continued to argue, for example, that the organics could not be completely explained away as nothing but Earth contaminants, and that the organic matter in the carbonates—which Romanek showed had formed on Mars—would surely have been destroyed if the temperatures had soared as high as some proposed.

“You have to understand the whole system,” Gibson would say. “They’ve been looking at it only from a geological point of view. Mother Nature had not only geology but atmosphere and water and other things in there, and that set the composition of the oxygen which allowed us to come up with a low temperature.”

As the controversy rolled on, this would become a recurring theme of the conflict. Some people liked to consider all the various threads of evidence in the rock together as a single story, others piecemeal. Was one to look at the forest or examine each tree separately? Did the evidence represent a coherent portrait of a complex, interacting system—or a mélange of isolated elements that had happened to get trapped together in a well-traveled vessel? How a person answered such questions would affect his or her conclusions.

The variety of interpretations also seemed to flow from the fact that even this one simple lump of minerals had more than a single history. Just as parts of it were contaminated with terrestrial microbes while others might not be, different parts of it gave differing answers to other questions too.

Steele was among those who objected to people applying the result from one fragment of the rock to the whole thing. The rock varied tremendously from one part of itself to another. Simon Clemett, for another, argued that the meteorite contained at least five different forms of carbonate minerals, possibly deposited into the different locations at different times or in connection with different events, some at higher temperatures, some at lower temperatures. It was the cliché—one hell of a microcosm.