The Rock From Mars (14 page)

The investigators also knew that the mere presence of the organics was not proof of life. This same substance could be created without a trace of biology, if things got hot enough. All you needed was a little “flame chemistry.” The stuff could be found in the smoke from a cigarette, in car exhaust, in interstellar gases, and in other places known to be quite devoid of anything alive, such as cosmic dust and bits of an ancient asteroid.

In March 1995, Kathie Thomas and other members of the group attended a planetary science conference in Houston. They caught up with Michael Meyer, NASA’s chief exobiology scientist. (Exobiology referred to studies of the prospects for life beyond Earth, and up to that point had been focused heavily on the study of the origins of life.) “Wait, wait, come here, we have some really interesting stuff!” they enthused. Meyer could tell they thought they had something pretty hot, but he cautioned them, saying that although the work was indeed interesting, “I’m skeptical, and you should be very careful. Because if you make an announcement about this, the press is going to run wild with it, and it doesn’t matter how many caveats you put in.”

In their presentation to the gathering, Thomas and the others described in general terms their discovery of possible organics from Mars. They acknowledged that they had more work to do to rule out the possibility that the organics had been added after the rock’s arrival on Earth. The crowd agreed. The reaction was one of subdued interest.
The Houston Chronicle
and other publications reported aspects of the Zarelab findings, noting that these organics were sometimes linked to the presence of living things.

The two laboratories went to work developing a stringent set of tests, controls, and clean-room procedures. Zarelab then repeated the experiments.

Simon Clemett and his coworkers spent months in a slough of tedium, trying to see whether or not they could rule out every alternative explanation for the presence of the organic compounds other than that they had been put there on Mars. Zare knew they couldn’t aim for complete certainty, since there was no such thing. But he wanted the maximum obtainable.

Zarelab acquired samples from other meteorites that had survived the same odyssey through the Antarctic ice as the rock from Allan Hills, the same laboratory processing, the same storage. The lab team did not find the same pattern in these other samples.

In the end, Zare and company agreed with the McKay group in Houston that they had a viable case to put forward.

For the McKay regulars, the Zarelab results marked a critical turning point. The high numbers on the organic molecules enabled the team to fill in and firm up their story line. The organics in the rock appeared to have come from Mars. They seemed to be of the same type and pattern as those produced by primitive microbes on Earth—and different from those measured in non-Martian meteorites.

Zarelab had found the first significant evidence of complex organic material from Mars—a major discovery by itself. It cast the 1970s Viking experiments in a new light and gave the first clear indication that the planet had the sort of chemistry out of which life could have arisen—whether or not it ever had.

At the same time, the McKay group was learning more about those spine-chilling little shapes and textures that so intrigued Romanek. (And they double-checked their findings by examining a second SNC—the Shergotty meteorite from Mars. Although they found no carbonate deposits, they did find in it forms similar to those nanofossil-like shapes they saw in the Allan Hills rock.)

In early 1995, just as Zarelab was injecting fresh oomph into the project, David McKay took over the heavy lifting on the scanning electron microscope. Chris Romanek had taken hundreds of pictures of the Martian samples, but in March that year, his fellowship at NASA ran out and Gibson was unable to hire him as a civil servant. Romanek left Houston to take a job with an ecology lab in South Carolina run by the University of Georgia, but he kept up consultations with Building 31 by phone.

Coworkers started to notice McKay working late at night in the e-beam facility—the first-floor complex that housed the various electron-beam instruments. To the concern of his wife and daughters, he would stay many nights until midnight or beyond, peering at the rock samples, too excited to go home.

He followed a familiar routine, moving efficiently among instruments and cabinets as he sat enthroned in a rolling lab chair. Wearing white latex surgeon’s gloves, he started by giving a white porcelain specimen dish a blast from a can of compressed gas called Dust-Off. He fished around in a plastic bag for a stainless steel container with Teflon lids, which might hold roughly a gram of meteorite. He opened it and tipped out into the specimen dish a single chunk, along with a skittering of loose dust grains, and inspected the chip to see if he needed to break it more. Then he slid the sample under a small binocular microscope with a fiber-optic light beam. The crumb of meteorite looked like a small mountain sitting in the white porcelain.

Sometimes, if the sample came from close to the meteorite surface, he could see a patch of the black fusion crust left by the rock’s violent passage through Earth’s atmosphere. From time to time, he made notes in his lab notebook, where he kept track of all his work.

McKay picked up a vacuum tweezer and sucked up a grain or chip of meteorite dust—a tiny speck to the naked eye, the most negligible-looking bit of nature. Next, he prepared a stub, made of carbon, aluminum, or brass, on which to mount the crumb. He used pliers to pry the top off an epoxy container, then squeezed out dabs of resin and catalyst onto a big rectangle of folded aluminum foil, using a toothpick to blend them. With his eye to a binocular microscope, he could watch as he dotted the mixture onto the stub. Then he took the vacuum tweezer (after blasting it clean with Dust-Off), and used it to pick up a speck of sample.

The next step was to coat the sample surface, so that it would show up properly under the scanning electron microscope. Because the instrument used electrons, not light, to “see” things, the process required its user to coat each sample with a conductive material—McKay often used gold and palladium—to prevent an unwanted buildup of electrical charge that would fuzz up the image. He always tried to avoid a clumsy application of coating, which could create lumps—shapes resembling bacteria, for example—that might be mistakenly interpreted as native to the sample.

Finally, the sample was ready for the scanning electron microscope. McKay passed the bits of meteorite, now mounted and coated, through an airlock inside the microscope complex—an assemblage of cylinders coming together at angles. He could lean down and look inside, through a porthole, to see the sample sitting there, at the base of the vertical column that contained the electron gun. He manually adjusted the tilt and focus, turned the voltage up to 15,000, and then rolled his chair a few feet to position himself in front of the computer screen where the magnified view of the sample would appear. Staring at the screen, and the menus of possible adjustments, he used his left hand to tweak knobs on a control board or to scoot a mouse around on the pad, fixing the alignment or correcting a blur.

Sometimes, the image on the monitor would show the aperture itself—a round black tunnel entrance. Then, with some tweaking of the focus, McKay would “dive” through to hard magnification, down the rabbit hole to the alien target terrain.

He used an X-ray device to study the composition of the material in the beam. When the device was on the “compo” setting, a spectrum-analysis graph appeared on the screen: bright red vertical lines—like flaming prairie grass growing along the bottom of the image—set against a brilliant blue field. The heights of the grass blades showed the abundances of various elements.

But the unpracticed eye could be misled. McKay knew that the spectrum was only partly due to the composition of the material under study. It was also, in part, the result of the geometry of the instrument setup, and the signal would get absorbed to a greater or lesser degree depending on how the sample was tilted.

On-screen, the scan appeared as a faint line moving down the image, like a veil slowly falling away. McKay liked to take a slower picture than most. He used the mouse to change the scan rate. When he was ready to capture an image, he punched a button labeled “Freeze,” the equivalent of the shutter button on a normal camera.

It was possible to go into a kind of reverie, working in the dim glow of the monitor, enveloped by the white noise of humming machinery. Hour after hour could pass, each moment full of anticipation for the next scene. Sometimes, McKay played music—Ireland’s ethereal Enya or other Celtic sounds, or a piano accompanying the sigh of spring rain.

McKay started “seeing things.” He glimpsed shapes that were just beyond the vision of his microscope, which was some fifteen years old and essentially obsolete. He felt frustrated. He knew that the engineers over in Building 13 had acquired an improved version. In late 1995, he talked to the branch chief there and worked out a time-share.

He had to compete with the engineers in the other building—all spit and polish compared to his cramped and threadbare complex—for microscope time. The engineers tried to be accommodating, but they were reluctant to let McKay and his team use the facility after hours or on weekends, citing security and safety concerns.

This convinced McKay to press for a similarly advanced instrument for Building 31, although it would cost more than half a million dollars—about triple the cost of his current scanning microscope. He would succeed, but not for two more years.

The instrument McKay coveted was a rare state-of-the-art electron microscope with a field emission gun, which fired a tighter beam. It was a brand-new technology, and the space center was one of the first places that bought one. The engineers used it to analyze cracks and other flaws in space shuttle flight hardware. Because the field gun generated an enormous beam of electrons (and the more electrons you fired, the smaller you could make your target), the instrument allowed you to see extremely fine details. It was a slower process than McKay’s microscope. Both operated at vacuum, but because you had to get more of the air out, this one required considerably more time pumping down the chamber.

Still, depending on how well the advanced instrument was tuned, McKay (the master tuner) could see things three or four times smaller than with the old microscope he had been using. Very nice, he thought.

McKay was among the first to use this technology for geological study, let alone biological investigation. Because this Martian meteorite was one of the first rocks ever looked at with this instrument, there was no record with which to compare his observations—no database of terrestrial rocks, or lunar rocks, or other meteorites. No way to know whether these features were common or rare. Some people would later contend that because McKay was treading such new ground, descending into a scale of smallness that was unprecedented in such a context, it was all too easy for him to misconstrue the meaning of what he saw there.

When he looked at the rock samples, McKay saw complicated forms, a lot of very fine textures. He could see variations of both the chemistry and the textures over a few hundred nanometers. And he was constantly thinking, as he always did when looking at a body of microscopic evidence, “What is this stuff? How did it form?”

One night in January 1996, Gibson joined McKay as he worked late with the powerful field gun in Building 13. McKay was zooming in on the black part of an Oreo rim when he saw something that jumped out at him. He moved aside so that Gibson could take a look. “Wow!” Gibson murmured excitedly. “What in the world . . .” They saw a shape that took their breath away. It looked segmented, like a Tootsie Roll or a worm.

The evidence had been mounting steadily. The team had begun to put all the pieces together by now—the greasy PAHs, the complex chemistry of the carbonate moons, the magnetic minerals, the suggestive mineral shapes. Now this. They were peering into a mineral landscape so incredibly small that the scale alone made it alien territory for the human eye. They were able to see details as small as 30 nanometers. The “segmented structure” (as they would call it) might have been a million times smaller than an ordinary bacterial cell. And yet—it looked more like the fossil of a long-dead Martian than anything they had yet seen in the rock. They looked at each other. This could be . . . something.

Over the succeeding months, McKay and Gibson would spot other shapes that they thought resembled Earth microbes—tubular or egg-shaped structures, or sometimes what looked like a school of microbes frozen in tandem undulation. They ranged in size from one-hundredth to one-thousandth the diameter of a human hair.

But this one would haunt them. After their spontaneous reaction wound down, McKay and Gibson set out to methodically document the size, location, and other aspects of this . . . segmented structure. Gibson would store the sample in a safe in his office.

That night, when they first saw the shape, Gibson in particular felt awestruck. When he got home his wife, Morgan, asked, “Is something wrong? Something at work?” He put her off, wanting to save it for later, after he had digested the implications. He had trouble sleeping that night. He would tell a vast audience about it the following year, saying it was “undoubtedly the most exciting thing I’ve done in my twenty-seven years as a scientist. I have to admit it does beat Apollo and the excitement there, and that was tough to do.”

Some days later, he laid the photograph of the “worm” down on the kitchen table casually, without saying anything, and his wife, with a background in biology, remarked offhandedly, “Hmmm, that looks like bacteria.”

The team members began to ask, “Why don’t we write it up?” “Isn’t it time?” In early 1996, they decided to publish their results.

The little band knew that they had not nailed their hypothesis definitively; nor were they sure that they ever could. They had no way of knowing even when they would take another major step closer to that goal. Although there were gaps and weak points, the team felt strongly that they finally had the underpinnings of a plausible, even compelling narrative: Once upon a time, tiny Martian organisms swam in fizzy Martian waters, their life (and death) processes spawning the combination of bug shit and slime and decaying matter and other stuff entrained in the carbonate globules as the water receded or evaporated, depositing these blobs in subterranean fissures in the rock.