The Rock From Mars (36 page)

Brasier spent close to one thousand hours peering down the microscope at the record-setting Schopf specimens. Starting in July 1999, Brasier’s group began searching for the discovery site in Australia and in 2001 examined the rock around the fossil beds in order to understand the context in which they occurred. Brasier found that the formation was not a continuous sedimentary formation but was split by lava flows.

In 2000, the Brasier group used a new computer program to build a digital database of the structures.

By late September 2000, Brasier had studied the shapes so intensively that he had started to see them in his
sleep.
It was then that he realized the structures were wrapped around spheres of glass, much as he had seen in other such formations in hydrothermal settings and hot springs. Brasier stared into the samples, not sure where to spot Schopf’s “microfossils.” The researchers began to draw and map every little structure in the rock, and saw that the supposed fossils were actually part of a wide spectrum of odd-looking shapes, most of them far too chaotic to be called fossils. And the appearance of cells as cited by Schopf, they concluded, was an illusion.

Brasier’s team decided, based on its own tedious geological mapping and chemical analyses, that Schopf’s specimens were actually nonbiological artifacts with no detectable organic matter, formed at a place where a primordial spring poured volcanically heated water from the seabed—a setting too hot for life and devoid of oxygen-producing photosynthesis.

The clincher, for Brasier, was that many of Schopf’s specimens were much more complex than he had portrayed them in his own published papers years earlier. Sure enough, Brasier saw some shapes that resembled cyanobacteria. But he was also amazed to find that some of the putative fossils were oddly branched or otherwise complicated—unlike cyanobacteria—in ways that Schopf had failed to describe. When seen in this full new light, they no longer looked like the bacteria with which Schopf had initially compared them.

It made you wonder if there had been a “terrible mistake,” Brasier would tell his audience in the hangar.

Now, in the first of two significant concessions, as he addressed the audience in the tent, Schopf acknowledged that he had initially mischaracterized the setting from which the fossils were taken. But this was based, he noted, on other people’s work. At first, in 1983, geologists had classified the locale “as a shallow marine near-shore environment,” but the site had been “recently reinterpreted . . . as being a hot springs fumarolic deposit. Everybody agrees on that.”

He and Brasier also agreed, he said, that he had published microscopic images of some forty-four specimens of these fossil-like structures, that they were petrified like other Precambrian microscopic fossils, that they were cylindrical, curvy, and had cell-like segments, and “that they range in form from what I would call good fossils to clumps of organic matter. We even agree on their composition.”

It was the exact nature of the organic matter about which the two sides differed, he said.

“There are some perceived problems here, of course,” he said, but he could explain them away. For example, as to Brasier’s claim that the filamentous shapes were not fossils, because they had formed in a hot springs fumarole, Schopf asked, “Why not?” Such specimens occur today in Yellowstone and at deep-sea fumaroles.

What about the apparent high temperatures at the site, which would be beyond the limit for life? That degree of heating had come later, he suggested, not at the time when the fossilized organisms were alive.

Another “perceived problem,” he said, was Brasier’s contention that the organic matter inside the fossils was chemically identical to organic matter not associated with supposed fossils but in the rock at large. This seemed to support the idea that they were all nonbiological artifacts. But Schopf countered that the particles scattered through the rock were bits and pieces of microbes, with the same geological history and coming from the same environment as the microbes that formed the fossils, “so of course they are chemically identical.”

Brasier and company had submitted the first version of their grenade of a paper to the journal
Nature
in February 2001, and they’d kept working on the samples. Meanwhile, the
Nature
editors sent Schopf a copy of the manuscript, as a courtesy.

Schopf counterattacked. First, he persuaded the Natural History Museum in London to ship him the complete set of his original Australian specimens for reanalysis. (The Brasier group, by contrast, had been obliged to spend several days traveling back and forth between Oxford and London, because the museum would allow them to borrow only three thin sections at a time. The one-way trip by bus took an hour and a half.) Schopf had recently teamed up with some of the few specialists in a new laser technique that, according to Schopf and his collaborators, could distinguish one type of carbonaceous deposit from another.

Rebutting Brasier’s claim that the fossil material had no detectable organics, Schopf reported in his own paper, also sent to
Nature,
that his new imagery showed that the fossil structures were rich in organic molecules and therefore must be microfossils.

Schopf sent Brasier his new findings. Brasier then revised his own paper to admit the presence of some kind of organic matter in the fossils. However, as the dispute over the Mars rock had so dramatically highlighted, not all organic molecules are produced by living things. Brasier argued in his revised paper that an extreme hot springs environment could have formed the organic molecules around the edges of crystals, from carbon monoxide and hydrogen, without the presence of life. His argument against Schopf’s “microfossils” was similar to the ones marshaled against the McKay group’s “nanofossils.”

Schopf was arguing that if the features were shaped like bacteria and were made primarily of organic carbon, this meant they had once been alive. Brasier, by contrast, compared that notion to “the Canals on Mars, or the Face on Mars. A superficial examination might make [Schopf’s argument] seem plausible.” But when viewed in their proper context, from the perspective of multiple disciplines, they failed to stand up to scrutiny based on the criteria that Schopf himself had put forward as far back as 1983.

Jabbing at Brasier rhetorically under the darkened tent in the hangar, Schopf went over what he called “inaccuracies” and “errors” in the Brasier paper and took up one of Brasier’s major points. First, he clarified some key definitions. “There’s been a great deal of confusion as to the use of these words and we ought to straighten that out,” Schopf said. “Kerogen is the fossilized insoluble organic matter in rocks. It is not a mineral. Graphite is a mineral. It is the crystalline form of carbon.” The point, he said, was that “these things are
not
made out of graphite.”

To prove it, he showed spectral data from twenty-five petrified fossils, ranging from as young as 400 million years to 3.5 billion years old, ranked from well preserved to poorly preserved, which he equated with “increasing graph-it-i-za-tion” (in professorial mode, he enunciated each syllable). The Apex chert—a type of flinty quartz—from which he had taken his fossils was in the lower midrange on this continuum, he indicated with the pointer, and was separated from the graphite objects. “Here’s the Apex chert. Here’s another kerogen,
another
one,
another
one,
another
one,
another
one,
another
one, and here, you start to get into graphite.” His fossils, he said again, with force, “are not made of graphite. They are made of kerogen.”

Now Schopf got to a particularly touchy issue—the true shapes of the supposed fossils. Brasier had argued that some of them rambled on and branched in ways that showed they were not blue-green algae, and in some cases not biological at all but actually a mineral extension of the quartz itself. Moreover, Schopf had failed to mention or depict these extended, filament-like shapes in his original papers a decade or so earlier.

On the question of branching, Schopf now asserted, “Dr. Brasier has used a new technique called Auto-Montage confocal microscopy. It is a really, really neat technique. The problem with it is it hasn’t been used in this science before. It condenses the focal plane so that objects that are not on the same focal plane can be seen as though they are. It gives an optical illusion, unless you’re rather careful.”

As McKay and Kathie Thomas-Keprta had learned, staring into the realms of the Lilliputians could lead to the same sort of parable as the blind men describing the elephant.

The shapes Brasier had taken to be branched—like the letter
Y—
were actually filaments that had folded back on themselves, Schopf argued—something like the AIDS-awareness ribbons worn on celebrity lapels. This structure (he pointed to a slide of a putative fossil) was suggested to be “anomalous. Here is the upper part of the filament. It curls down beneath it. Here is the upper focus. Here is the lower focus. It is not branched at
all.
It, in fact, is a folded-over filament.”

By now he was speaking with apparent irritation, as if trying to explain something to a frustratingly slow child, his voice rising occasionally.

“The third example is more difficult to show. . . . But there is no attachment here whatever. Yet if you look at their paper, it is, uh, suggested, it is
said
that the thing is branched and attached. Well, there is no attachment. There is no organic matter there.

“And the fourth example is shown here. This is said to be a branched filament. And the question is about this little bit here, and you can see that in fact it is a torn filament. This little bit fits back into the side of the filament
just like Madagascar fits into the southeastern corner of South Africa, for goodness sakes!
” He was fairly growling by the time he got to the word
Africa.
“This thing is not branched. It’s made of cells, as you can see.

“Okay.” He took a breath. “Well, the question before the house then becomes, how does one solve the matter of biogenicity?” Were these fossils from Earth’s earliest life or were they formed without benefit of biology? “Now, this is a quote from the Brasier et al. paper, and what it says is you reject fossils if a possible nonbiologic source can be proposed. And I suggest to
you
that this represents flawed reasoning. I suggest that, because, the way this game is played, you propose what the fossils might be but you do
not
show in fact what they are.”

Schopf next invoked his own youthful initiation rites.

“Now, we’ve been down that path before. And that war was won by Elso Barghoorn in the 1960s. He stood before the world
by himself
and he showed the Precambrian fossils are indeed fossils. And how did he do that? He said that the biologic origin of the fossils is shown by the traits they exhibit that are
unique to life,
traits shared by fossils and living organisms but
not by inanimate matter.
That is the way that this matter ought to be solved. That’s the way to do this science.

“So the point of disagreement, the single important point of disagreement, comes down to simply this. Dr. Brasier and his colleagues say the fossils are pseudofossils, graphite formed nonbiologically by . . . an abiological synthesis.

“We say that the fossils are microbial fossils, kerogens formed by ancient organisms. So, let us look then at the plausibility of those two proposals.

“In the first place . . . no nonbiological particulate organic matter has ever, ever been recorded in the geologic record of the Earth. So this is an extraordinary claim.

“Secondly, there is no plausible environment, no natural plausible environment”—he gestured with both hands palms up, beseeching—“in which such things could produce such amounts of organic matter.” He noted ways to do the type of synthesis in question in the laboratory, adding, “But, folks, those things don’t occur normally, hardly at all, in nature.” The sites that organic geochemists and micropaleontologists “have both worked the
most
on this planet are petroleum deposits. We’d
know
”—here he extended one arm to point at the slide on the screen—“if there were such ‘sports’ of nature there. They are not there.

“And finally the isotopes show that it’s not
at all
abiological carbon” or it would have a different signature, he said. “Look, these things are made out of coaly kerogen”—he punched each of the next eleven words as if it were a separate sentence—“
just like every other petrified Precambrian fossil that’s ever been found.
” Schopf took a quick, deep breath, then noted the few exceptions.

“The complexity rules out a nonbiologic source. There are many specimens, one hundred and eighty specimens . . . fifteen examples on average of each type. They
vary
like living microbes, they
grew
by cell division, they
inhabit
a livable environment, and their isotopes show they are biological.”

He next outlined evidence from other deposits, within 100 million years of the same age, in which fossils were found, in order to show that his fossils were not an isolated phenomenon.

Then his voice subsided. “So,” he summed up, “they’re made out of [coal-like] organic matter, the complexity rules out a nonbiologic source, there are many specimens, they vary like living microbes, they grew by cell division, they are in a livable environment, their [isotopic signature] is unquestionably biologic. In addition, they are chemically the same as
undoubted
fossils in twenty-four other units [of rock] that fit the continuum of geochemical maturation. We
understand
the history of that organic matter. It fits all evidence of a similar age. And I come back to Professor Barghoorn. He solved this problem. He said, if it looks like life, if it’s made of the molecules of life, if it has the isotopes of life, if it fits with all other evidence of life, well, folks, most likely it’s life.”

The audience applauded, and sat back for round two.