The Rock From Mars (34 page)

The situation reminded Thomas-Keprta of a scene in the movie
Toy Story,
which she and her son had watched too many times to count. The kids are coming up the walkway to a party, one holding what looks like a tiny gift. As the kid turns, the gift shape-shifts and, it becomes clear, is enormous. It was all in the viewing angle. That’s what Thomas-Keprta was coping with in the crystals, only more so. From one angle, you saw a square; viewing it edge-on, you saw a rectangle; and if you were looking at an end point, you saw a hexagonal shape.

The team would figure out the orientation of a crystal—which axis they were looking down—by studying the planes of its atoms. Then they had to look at the same crystal from dozens of different perspectives. They would rotate the crystal through a series of angles with a known relationship to the plane of the image. The final product—the imagery—was something like stop-action photography: a series of partial views that collectively, ideally, added up to a more complete picture.

Over the years, Thomas-Keprta had watched the apparent geometries of these magnetic crystals flicker and change as if in a kaleidoscope. Were there bubbles? Bullet shapes? Parallelepipeds? When she viewed a specimen from one angle, she could see that the atoms lined up in planes.
Tilt:
a supposedly telltale “whisker with a screw dislocation” (that geometry known to be nonbiological) would reveal itself to be a flat plate.
Tilt:
a rectangular crystal became a hexagonal prism—like an elongated stop sign.

Now she was able to see more clearly than ever before. And she could see that something was off. In the early 1980s, a British chemist had established the shape of the magnetic crystals in the MV-1 bacteria to be sort of a hexagonal column. But she and her coworkers, huddled over their new images of those MV-1 crystals, thought that wasn’t quite right. That wasn’t the shape. When they compared the MV-1 images with the images of Bingo, their perfect crystal from the Mars rock, the two sets looked exactly like each other—but neither seemed to fit the widely accepted model for the shape of the crystals made by the terrestrial microbe MV-1.

Thomas-Keprta, with major assistance from Clemett (who had left Zarelab to work in Building 31), puzzled and fretted over the problem. Well, maybe at the edges the shapes were just fading away because the carbonate was covering them. Maybe, in other words, these crystals did come to a point at the edges, just as the British model suggested, but the observers weren’t able to see it clearly. But—no, the shapes did seem to fade at the edges. There was something they were missing.

It was one of those irritating misfits, one of those confounding obstacles that sometimes pointed the thoughtful investigator toward new ground.

Thomas-Keprta and Clemett debated what to do. They were eager to submit their new paper to the National Academy of Sciences journal, but how were they going to handle this conflict over the shape? Just note it and move on?

Thomas-Keprta left work at the end of that day in a state of frustration. Clemett had drawn up an image of the crystal shape. She took that home with her. She sat down at her dining room table and started cutting out shapes like paper dolls, trying to make diagrams that would fit, trying to overlay the shapes. The hours passed.
Was
that 1980s model correct? Her MV-1 images didn’t fit it, and neither did her Mars rock images, but the crystals in her MV-1 and Mars rock images looked like each other. Why isn’t this right? she asked herself. What’s going on? She went through the information, over and over and over.

Her husband found her still slumped there at the table the next morning. “What are you doing?” he asked, exasperated. She told him what she had decided. “This isn’t right. This doesn’t work. I can’t put this paper out. This just isn’t right.”

She showered, changed, grabbed some breakfast, returned to Building 31, and told Clemett the same thing. “This doesn’t work. There is another ‘face’ in here.”

But now she had the key.
“We’ve got to shave off the corners!”

Cutting corners would be a good thing in this case. If they cut the corners off their model of the crystal shape, leaving new geometric faces where before there had been points, she told him, “It will all make sense. It makes sense for MV-1. It makes sense for [the rock from] Allan Hills. Everything will fit perfectly. The old model is wrong.”

The realization came equipped with another incantation, like the one that had floated through Duck Mittlefehldt’s head during the steamy summer of 1993, leading him away from asteroids and on the trail to Mars. This time, instead of “Shergotty, Nakhla, and Chassigny,” the phrase was “truncated hexa-octahedron.” It was a shape with eight octahedral faces, six hexagonal faces, and six cubic faces. Kathie Thomas-Keprta figured hers would be the first report of any crystal having this particular shape.

But why would nature “select” such a configuration?

The answer her team proposed was that the addition of extra faces, in the case of MV-1, served to elongate the shape, and this elongation enhanced the magnetic pull of the little compass, making the bugs more efficient at locating food and energy sources. The truncated hexa-octahedron could be described as a microbe’s evolved design for building the best magnet possible with the least amount of iron.

So, of the hundreds of crystal grains they’d studied from the rock, the team concluded that some 28 percent were identical to those found in the Earth bacteria—and they had to have come from Mars. In the bargain, the team was presenting evidence that the geometry of biomagnets manufactured by these Earth bacteria was different from what scientists had thought for some fifteen years.

Again, it was well known that magnetic crystals could be formed in nonbiological processes. But the ones formed in that manner seemed to be demonstrably different not only in shape but in other ways—size, purity, and quantity of defects—from those produced by bacteria. No one had ever detected any nonbiological crystals, natural or laboratory made, that displayed all the properties of the biologically formed crystals Thomas-Keprta’s group had studied and was describing in the paper.

Taking into account those properties—the chemical purity and lack of defects, the distinctive size and shape—Thomas-Keprta and her coworkers concluded that there were no known nonbiological sources for this special population of magnetic crystals nested inside the carbonate moons inside the Mars rock.

Thomas-Keprta, for one, was completely convinced she was seeing signs of Martian biology. To her, the evidence was stunning. The crystals in the rock were Martian “magnetofossils,” she wrote in the new draft of the paper, which she was now ready to release to the world—and defend.

What she felt after her night of inspiration, however, fell a bit short of the classic, theatrical
Eureka!
thrill. It was something more akin to sweaty-palmed relief. “You caught your paper just before it would have gone out wrong!” she told herself. “Oh, my gosh, I just avoided disaster!”

On February 27, 2001, the second, shorter paper was published in a special astrobiology issue of the
Proceedings of the National Academy of Sciences,
with Thomas-Keprta as the first of ten authors. “Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process,” the paper concluded. “As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.”

There in the journal was Bingo in all its glory, albeit looking more like a smudged thumbprint than a history-making crystal form.

Joseph L. Kirschvink, a Caltech geobiologist who was one of the coauthors, said of the paper, “The process of evolution has driven these bacteria to make perfect little bar magnets, which differ strikingly from anything found outside of biology. In fact, an entire industry devoted to making small magnetic particles for magnetic tapes and computer disk drives has tried and failed for the past 50 years to find a way to make similar particles.” He added, referring to the Martian crystals, “A good fossil is something that is difficult to make inorganically, and these magnetosomes are very good fossils.”

MV-1 expert Dennis Bazylinski, another of the paper’s coauthors, suggested that the magnetite crystals might turn out to be broadly useful to astrobiologists and geobiologists as markers for the presence of biology.

Their claims got an independent boost from a second finding described in the same issue of the
Proceedings,
by an international team led by biologist E. Imre Friedmann, of Florida State University, another veteran of Antarctic research campaigns. One of the first to use the scanning electron microscope for studies of bacteria, Friedmann was best known as the discoverer of rock-dwelling microorganisms. He had detected blue-green algae, or cyanobacteria, living inside desert rocks in Israel’s Negev and the American Southwest. And in sixteen or so field expeditions to Antarctica, he had done extensive studies of life in rock.

Friedmann had been impressed and intrigued by the McKay group’s work on the Martian meteorite. While he knew it was unlikely that one random rock could provide “the answer” to the riddle of Martian biology, he believed their 1996 paper had precipitated events that would lead, at the very least, to a clarification of the question of whether life had been present on Mars. Now the Friedmann group’s studies seemed to fill in a key piece of the magnetic puzzle.

For years, skeptical scientists had challenged Thomas-Keprta’s claims of biological origins for the magnetic crystals on grounds that she had never detected the telltale choo-choo train formation that characterized magnetic devices found inside Earth bacteria. Now Friedman was claiming they had it.

Friedmann’s group studied the crystals under an electron microscope using a technique that enabled them to “see” the tiny chains in position inside the meteorite. What they saw were the crystals lined up “somewhat like a string of pearls,” as Friedmann put it, or, as another scientist observed, sort of like “teeny backbones.” This was how they appeared inside organisms on earth—like vertebrae running along some fraction of the creature’s length.

The team could see fossilized outlines of both the chain and the membrane that had shaped it, Friedmann reported. “The chains we discovered are of biological origin. Such a chain of magnets outside an organism would immediately collapse into a clump due to magnetic forces,” he said. The chains, in this scenario, were preserved in the meteorite long after the putative bacteria themselves decayed.

The group also concluded that the individual crystals were of similar size and shape and did not touch each other, and that the chains they formed were flexible, presumably in order to be able to move with the organism as it swam—all further signs of biological origin.

Friedmann said the discovery marked a potential turning point for understanding all life. “Until now, studying life has been like trying to draw a curve using only one data point—life on Earth. Now we have two data points to draw life’s curve.” He said the next step would be to find the remains of the bacteria themselves.

This time (in contrast to the quiet that greeted the McKay group’s longer, technical paper published a month or so earlier), attention was paid. NASA, the National Academy of Sciences, and the universities of participating investigators issued press releases. The rock vaulted back into the headlines, and jump-started a new round of investigations in far-flung laboratories.

The new findings were widely professed to be intriguing. But, inevitably, many scientists resisted the pull of the Martian magnets, raising questions about the latest claims—particularly Friedmann’s—and gearing up to put them to the test.

This was how the process worked. All these people labored in the borderlands of the unknown, on the cusp of the contentious assertion, where every answer led to more questions. Once they reached the territory of textbook certitude, they would be out of their element, and they would move on to another frontier.

Astrogeophysicist Chris McKay (no relation to David McKay) had long been in the “why waste time” camp when it came to the debate over the Mars rock. The evidence seemed conclusively inconclusive.

Now, he thought, people might move from
debating
David McKay’s hypothesis to regarding it as a
working
hypothesis for further research. “I guess you can move me from the skeptical camp,” he said, and into the one that says, “
maybe
this is starting to get serious.”

One of the most outspoken critics, once again, was the leader of the Antarctic meteorite search, geologist Ralph Harvey. He told the Associated Press, space.com, and other outlets that the story of the rock was still far from conclusive. “It has all boiled down now to this magnetite.” So what if these things have never been found in an inorganic setting, he asked. “The truth is that we haven’t looked. It’s hard to prove a negative hypothesis. It’s hard to test it, but it is essential. It’s the difference between science and faith.”

Planetary scientist and biogeochemist Andrew Knoll remarked in an e-mail, “I wouldn’t touch Mars magnetite with a ten-foot pole. There’s simply a lot we need to know before making firm interpretations of that material.”

Several studies soon challenged the biological scenario anew.

In an awkward turn for some of those involved, one of the most direct assaults on Thomas-Keprta’s conclusions came from another group of scientists inside Building 31. They were hard at work trying to show that magnetites with the same “uniquely biological” geometry found in the Mars rock could be made in the laboratory—without biology. And if that wasn’t close enough to home, the supervisor of the work was Gordon McKay, David’s younger brother.

It was not exactly a coincidence, since David McKay had commissioned that group as part of his Blue Team—one of the two opposing groups he had set up to provide balance.