The Rock From Mars (55 page)

By late September 2000
• Brasier e-mail to author.

Now, in the first
• Schopf said in an e-mail to the author, May 6, 2005, that, actually, there has been continued disagreement as to the type of environment that existed at that site, hydrothermal or otherwise, but that it has been mapped by at least four sets of scientists. He added, “I am agnostic. They will work it out.”

Schopf counterattacked. First
• Rex Dalton, “Microfossils.” In addition, Steele, in an interview with the author, described one of Schopf’s writings as a seventeen-page “diatribe” objecting to the Brasier group findings. He said Schopf reprimanded the museum curator for giving out the samples.

Schopf sent Brasier
• In an e-mail to the author, May 6, 2005, Schopf said he had sent Brasier “a copy of our manuscript out of courtesy. . . . I did what I thought was honest and right. I gave him our data and showed that he had been mistaken. Got nailed for it. But I can live with that. I would do it again. Help the science, if you can.” Also see Dick and Strick,
Living Universe,
p. 199, for a succinct summary of the Brasier-Schopf dispute.

Brasier, by contrast, compared
• Brasier e-mail to author.

On the question of branching
• Although Schopf criticized the Brasier group’s use of the confocal microscopy technique, Everett Gibson told the author in an e-mail that Schopf embraced the approach at the April 2005 NASA Astrobiology Meeting at the University of Colorado, Boulder. “Schopf went out of his way to praise confocal microscopy as a ‘new and powerful’ technique to study the fossil record,” Gibson said. “It seems that unless he is using the technique, it isn’t worthy. . . . An amazing switch on his part.”

The shapes Brasier had
• Morton, “Secret of a Rock,” p. 43, uses the metaphor of the AIDS ribbon.

As Schopf had acknowledged
• Schopf,
Cradle of Life,
p. 98.

Brasier had gone to
• Schopf told the author in an e-mail, May 6, 2005, that “despite Dr. Brasier’s assertion, I know of no paper he has ever published on modern microbes, modern microbial assemblages, fossil microbes, fossil microbial assemblages. He has, to my knowledge, never discovered any new Precambrian microorganisms, never described such organisms, never named such organisms,” nor studied fossils preserved in a manner relevant to the Apex fossil dispute. “To the best of my knowledge,” Schopf said, Brasier’s work, rather, has concerned more complex Phanerozoic fossil microorganisms.

For his part, Brasier
• Author interview with Brasier and e-mail exchange with Brasier, early 2002.

Almost three months later
• Rex Dalton, “Microfossils.”

The dispute would continue as to whether or not the fossil shapes branched in a way that suggested they were not a product of biology. But Schopf, for one, would later declare the matter closed. In an e-mail to the author, May 6, 2005, he declared that “the branching business has been solved, and published (with photos also of the mineralic artifacts described in her notes as branching things by Bonnie Packer.)” See J. W. Schopf, “Earth’s Earliest Biosphere: Status of the Hunt,” in P. G. Eriksson, W. Altermann, D. R. Nelson, W. U. Mueller, and O. Cateneanu (eds.),
The Precambrian Earth: Tempos and Events,
Developments in Precambrian Geology 12 (Amsterdam: Elsevier, 2004), pp. 516–39. “In truth,” Schopf went on, “Bonnie Packer never showed me pictures of any branching fossils, simply because none of the fossils (not one) branch.”

Schopf also pointed out in the e-mail that he and Bonnie Packer had published another paper (J. W. Schopf and B. M. Packer, “Early Archean [3.3 billion to 3.5 billion year old] Microfossils from Warrawoona Group, Australia,”
Science,
vol. 237 [1987]: pp. 70–73) in which they reported “the finding of microscopic fossils both in the Apex chert and in a second chert unit of about the same age some 40 km to the west. It is incorrect to give the impression that she (or anyone else who studied those fossils at that time) had any misgivings whatever as to their biogenicity.”

“Okay, let me explain
• Schopf told the author in an e-mail, May 6, 2005, that Steele and Brasier “have consistently misrepresented my views” as to the question of whether those early microfossils represented cyanobacteria or not. However, Steele and others told the author that Schopf has—if not in his published paper in 1993, then in numerous talks and presentations—given the impression that his findings suggested fossil cyanobacteria at an unexpectedly early period. Still others say they believe that Schopf, in those instances, was simply responding to pressure from people eager to know what those early fossils had looked like, and “pond scum” had seemed a good bet.

Schopf pointed to the following passages from his paper—“Microfossils of the Early Archean Apex Chert: New Evidence of the Antiquity of Life,”
Science,
vol. 260 (1993): pp. 640–46—to support his argument that he had left the question open at least in that initial description (boldface added by Schopf):

•                  (p. 643): “Because the affinities of these fossils in the Procaryotae [nonnucleated prokaryotic bacteria]
cannot be demonstrated unequivocally, I formally describe them as prokaryotes
incertae sedis
[viz., prokaryotic microorganisms of uncertain systematic position]; and because the phylogenetic relations between them and the much (1,300 to 2,800 million years) younger, predominantly cyanobacterial fossil taxa to which they bear specific resemblance
are therefore undetermined,
they have not been referred to previously described Proterozoic species.”

•                  (p. 644) reads as follows: [after discussion of lines of evidence consistent with oxygen-producing photosynthesis] “These additional lines of evidence, however, are not conclusive; all the latter, which necessarily incorporates model-dependent uncertainties,
would be equally consistent with the presence of solely anoxic bacterial photosynthsizers.
Moreover, it is conceivable that the external similarity of the Apex microorganisms to younger oxygen-producing oscillatoriaceans masks significant differences of internal biochemical machinery;
thus, their morphology may provide a weak basis on which to infer paleophysiology.
To address this issue, additional data are needed.”

A few weeks later the journal
• Rex Dalton, “Microfossils”; see also Richard Kerr, “Reversals Reveal Pitfalls in Spotting Ancient and E.T. Life,”
Science
(May 24, 2002): pp. 1384–85. See also Dick and Strick,
Living Universe,
p. 199, which notes that Jill Pasteris, of Washington University, an expert in the laser-Raman spectroscopy used by Schopf in his defense, raised objections to Schopf’s interpretation. See also Kenneth Chang, “Oldest Bacteria Fossils? Or Are They Merely Tiny Rock Flaws?”
New York Times,
Mar. 12, 2002, p. D4. That account quotes Harvard scientist Andrew Knoll as saying that many paleontologists had long doubted whether Schopf’s shapes were fossils. After the Brasier paper, he said, “I think the preponderance of evidence is that they are not.”

Others agreed
• Dick and Strick,
Living Universe,
p. 200.

Andrew Steele would come
• Author interview with Steele.

Even as researchers
• Author interview with Schopf; e-mail from Schopf to author, May 6, 2005. See also Schopf’s abstract, “The Archean Fossil Wars: Why Science Has Won,” prepared for the January 2005 Gordon Research Conference in Ventura, California.

In any case, Schopf took issue with those who saw the Apex fossils as his foremost achievement. “The Apex fossils do not rate,” he said in the e-mail. “Heck, in 1965, Professor Barghoorn and I reported the presence of fossils 3.1 billion years old; others followed suit; the Apex assemblage is of interest only because it is old and morphologically relatively varied.” Through fieldwork and interaction with local scientists, Schopf had also been able to discover the first or oldest Precambrian stromatolitic fossils in China, India, Australia, South Africa, and South America, and could point to numerous other accomplishments.

CHAPTER FIFTEEN:
down the rabbit hole

McKay happened
• Author interview and lab sessions with McKay.

But much of the time
• Roughly every two years, Earth and Mars come as close as about 40 million miles (65 million kilometers) apart. When they are on opposite sides of the sun in their orbital tracks, they can be over 200 million miles apart. See William K. Hartmann,
A Traveler’s Guide to Mars
(New York: Workman, 2003), p. 174.

In detailed three-dimensional
• For one attempt to show the true colors of Mars, see
National Geographic,
Feb. 2001, p. 39. A graphics team corrected an early uncalibrated color image from the Viking 2 lander, tweaking brightness and contrast, to show “how Mars might look to a human visitor”—at least in that location, on that day in 1976.

Decades of Mars
• Recent studies from orbit had turned Mars from a “flatland” world into a three-dimensional realm, with a “layer-cake” structure, dust-driven weather, and a clear water cycle. (Author interviews and e-mail exchange of July 5, 2000, with NASA’s chief Mars scientist, James Garvin.) The branching channels and other evidence that water once flowed on Mars all dated from the same ancient period, called Noachian (after the biblical Noah of the great flood), which ended about 3.5 billion years ago. In the late 1990s, the Mars Global Surveyor detected thousands of seepage sites that might be linked to surface water runoff in the modern era.

The rovers were
• Mars science team leader Steven Squyres, of Cornell, in press briefing, Jan. 3, 2004; see also Squyres et al., “Opportunity at Meridiani Planum,”
Science
(Dec. 3, 2004): pp. 1633–1844, in which eleven reports by 122 authors describe results from the Opportunity mission. “Liquid water was once intermittently present at the Martian surface at Meridiani, and at times it saturated the subsurface,” wrote Squyres, Ray Arvidson, and others. “We infer conditions at Meridiani may have been habitable for some period of time in Martian history.” The rovers were also turning up welcome evidence of minerals known (on Earth) to be good at preserving evidence of ancient life for vast periods of time.

In keeping with
• Mars mission scientist Maria Zuber of MIT, Carnegie Institution lecture, “Climate Change on Mars,” Nov. 4, 2004, and author interview.

(In early 2005, European
• See John B. Murray, et al., “Evidence from the Mars Express High Resolution Stereo Camera for a Frozen Sea Close to Mars’ Equator,”
Nature
, vol. 434 (March 17, 2005): pp. 352–56. The finding would require further confirmation to show that the signal was not coming from hydrated minerals rather than water ice.

At the same time
• Author interview with Meyer, who took the reins of the Mars exploration program in late 2004. For more on the Martian wobble hypothesis, see also Hartmann,
A Traveler’s Guide to Mars
, pp. 236, 248–49, 297–98, and 352. Earth’s seasons are determined by the tilt of its axis—the line through the north and south poles—as it circles the sun. Earth and Mars are currently tilted at about 23.5 and 25 degrees, respectively, relative to the sun. Scientists believe Earth may have been spared the disruptive wobble by the steadying influence of its moon. (The two Martian moons are too tiny.) Some scientists also suspect that the Martian dip, initially even wilder, may have been dampened by the effects of a huge concentration of lava in the bulging Tharsis region, which deformed the planet early in its history.

But were the signs
• Studies of sudden, catastrophic floods on Earth concluded that similar water action—brief and massive—formed the great river channel of Ares Vallis—at whose mouth Pathfinder had landed in 1997—and many of the other Martian outflow channels. See Hartmann,
Traveler’s Guide to Mars,
pp. 222–23. Hartmann cites studies by Arizona hydrologist Vic Baker and U.S. Geological Survey scientist Michael Carr.

There were also possible signs of persistent water action on early Mars: a meandering streambed—a feature that takes a long time to form—for example. And studies of the Martian watershed showed that if Mars had abundant water, it would have drained into the northern hemisphere, which is flatter than the American Midwest. The only comparably flat areas on Earth are the abyssal plains beneath its oceans. (A well-known image of a quasi shoreline was still considered equivocal, however, because the “bathtub ring” could have been left by lava flow instead of water.)

Key pieces of
• Zuber lecture. If there was a Martian ocean, it should have left a chemical signature—such as calcium carbonate all over the surface.

Such highly acidic waters
• Author interview with NASA’s Michael Meyer. For a brief further discussion of the missing carbonates, see Hartmann,
A Traveler’s Guide to Mars,
pp. 147–48.

The bad news for
• Squyres et al., “Opportunity at Meridiani Planum.”

Alternative approaches to the
• Author interview with McKay; see also NASA Ames press release, September 22, 2003, on the Rio Tinto project. Called MARTE (Mars Analog Research and Technology Experiment), it was led by Carol Stoker, of the Ames center, with support from the Spanish government.

He had joined a
• The team leader was Marjorie Chan, head of the University of Utah geology department. See Chan, et al., “A Possible Terrestrial Analogue for Haematite Concretions on Mars,”
Nature,
vol. 429 (June 17, 2004): pp. 731–34.

The new plan called
• Author interview with NASA Mars chief Meyer.