A Brief History of Creation (35 page)

By early 1996, NASA officials were confident they could make a case that ALH84001 did, in fact, contain compelling proof that life had existed at some point in Mars's distant past. McKay and NASA officials planned to hold a press conference announcing their findings, timed to coincide with the publication of a paper detailing the discovery that had been submitted to
Science
. Their plans were almost stymied by a high-priced call girl named Sherry Rowlands. Rowlands had learned of the discovery from Clinton political adviser Dick Morris, who had been privy to White House briefings about it. She tried to sell the story to the tabloid
Star
, but the reporter viewed the story as too fantastic and Rowlands too unreliable.

Rowlands was not the only person Morris had shared the secret with. Eventually, the story was leaked, and newspapers around the world hailed the discovery of extraterrestrial life. President Bill Clinton hastily called a press conference to herald the discovery. “Today Rock 84001 speaks to us
across all those billions of years and millions of miles,” he announced. “It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered.”

Possible Martian fossils on ALH84001.

Yet the final judgment about the significance of ALH84001 by the scientific community was still to come. Over the next few years, a chorus of naysayers would emerge. Many would come to see the episode as reminiscent of the hoopla surrounding another meteorite that had sparked excitement a century and a half earlier.

T
HE NOTION OF
a universe teeming with life is certainly nothing new. As far back as the fifth century BC, the Greek philosopher Anaxagoras had put forth the idea that the seeds of life were scattered about everywhere throughout the cosmos. He called this concept
panspermia
, “life everywhere,” and it was later popularized in the poetry of Lucretius. Eventually, the term came to refer to the belief that life had initially developed elsewhere in the solar system, and at some point migrated to Earth via meteorites or as space-borne spores.

The theory of panspermia became particularly widespread in the nineteenth century, when it was championed by two of the most respected scientists of the age: the Swedish chemist Svante Arrhenius, one of the first directors of the Nobel Institute; and Lord Kelvin, whose low estimates of the age of the Earth had stymied Charles Darwin. Kelvin was a particularly enthusiastic supporter of the theory and had made the case that such life was responsible for initially seeding life on the Earth. “We must regard it as probable in the highest degree,” he once wrote, “that there are countless seed-bearing meteoric stones moving about through space.”

As was the case for many who shared his belief in panspermia, Kelvin's interest had been piqued by one of the most famous meteorite controversies in history. On a spring evening in 1849, a bright fireball was observed streaking over the skies of southwestern France, accompanied by a sonic boom. When it impacted the Earth's atmosphere, it smashed into at least twenty pieces near the small village of Orgueil. One by one, the meteorite
fragments were recovered by the villagers, who had watched the whole episode in amazement. A little more than 25 pounds of rock was collected, soft enough that it could be cut with a knife and used to write like a graphite pencil. Soon a parade of top French chemists had taken turns examining the rock, including Marcellin Berthelot, whose work synthesizing organic compounds had made him one of the best-known chemists in the world. Berthelot and many other scientists concluded that the meteorite fragments contained materials of biological origin, and thus that somewhere beyond the Earth, life must also exist.

Eventually, Louis Pasteur was called on to give a definitive opinion as to whether the Orgueil meteorite indeed contained signs of life. It was just five years after Pasteur had convincingly disproved the notion of spontaneous generation, and he was already well on the way to his status as France's experimenter par excellence. Pasteur suspected that contamination on Earth might have been responsible for the startling results seen by Berthelot and others. He decided to build a special drill that would enable him to see whether the organic compounds found in previous studies were present only in the outer layers, and could thus be chalked up to terrestrial contamination, or were also present on the inside, which would presumably show that the substances were indigenous to the meteorite. Pasteur could find no trace of microbes inside the meteorite, and he concluded that there was no evidence for biology in the samples. The clamor of interest that the Orgueil meteorite had excited soon subsided.

The Orgueil meteorite spent the next century as nothing more than a museum curiosity. Then, a pair of American scientists, Bartholomew Nagy and George Claus, decided to take another look. They were surprised to discover small, cell-shaped structures that they interpreted as fossilized alien microbes. In 1962, they reported their findings in
Nature
. The discovery was met by considerable skepticism from almost every credible scientist. The Orgueil meteorite had by then spent nearly a century on Earth in completely nonsterile conditions, sloppily curated in dusty museum drawers. Any clues pointing to the existence of life on the rock had long since been compromised. Nevertheless, a lively debate carried on for two years in the scientific literature.

In 1963, a symposium discussing claims for evidence of life in the Orgueil meteorite was convened at the New York Academy of Sciences. The meeting was presided over by none other than Harold Urey, by then the grand old man of exobiology, and attended by various luminaries in the study of micropaleontology, meteoritics, and the origin of life, including Sidney Fox. As the meeting progressed, some of the objects were debunked as nothing more than common ragweed pollen grains that ubiquitously waft through air. Other particles, however, defied explanation. They were unlike anything found on Earth. But were they truly evidence of extraterrestrial life?

The debate eventually turned to the question of size, the same point of contention that was later resurrected when scientists debated the evidence for Martian life in ALH84001. Some at the meeting were convinced the odd microstructures looked like things that had been alive. Naysayers in attendance said they were no more alive than Sidney Fox's microspheres, and were perhaps derived by the same processes. Urey, ever the open-minded skeptic, concluded the meeting by declaring himself unsure about Orgueil but calling for greater efforts to search for signs of life in meteorites: “The study of carbonaceous meteorites for life-like forms is not an unreasonable pursuit, particularly when one considers that the United States plans to spend 25 billion dollars to put a man on the moon.”

In the 1960s and 1970s, interest in panspermia was revived first by the paper in
Icarus
written by Francis Crick and Leslie Orgel, and later by the astronomers Fred Hoyle and Chandra Wickramasinghe. Both ideas came to be seen as borderline absurd in the eyes of their scientific peers.

Crick and Orgel had never really treated their model as anything more than fanciful speculation. Hoyle and Wickramasinghe, however, were deadly serious. They proposed that viruses were constantly being delivered to Earth on meteorites. Such viruses, they said, could have been responsible for the flu pandemic that killed between 50 million and 100 million people in 1918. Certain outbreaks of mad cow disease, polio, SARS, and even AIDS might also have originated off-world.

Hoyle was best known as the scientist who, during a 1949 interview on the BBC, had coined the term “Big Bang” to describe what would become the dominant theory of the origin of the universe. Yet by the time of his
work on panspermia, he had become nearly as famous for being one of the last holdouts against the Big Bang theory, even though in the years since he had given it a name, overwhelming observational evidence had made the theory a cornerstone of modern cosmology. Nor was Hoyle's cause helped by the fact that he was also a popular science fiction writer in his spare time. Some called his “viruses from space” idea nothing more than an extension of the plot of his 1957 novel
The Black Cloud
. Given the abundance of competing and far more plausible hypotheses about the origin of viruses, Hoyle and Wickramasinghe's ideas were largely ignored.

A
FEW DAYS AFTER
NASA's ALH84001 announcement found its way into newspapers in 1996, the evolutionary biologist Stephen Jay Gould penned an editorial for the
New York Times
entitled “Life on Mars? So What?” Gould argued that the discovery of life on Mars shouldn't surprise anyone. He had his doubts about specific claims regarding ALH84001, but the crux of his argument was that life on Mars was no more improbable than life on Earth, which had happened “almost as soon as environmental conditions permitted. . . . The origin of life may be a virtually automatic consequence of carbon chemistry and the physics of self-organizing systems, given favorable conditions and the requisite inorganic constituents.”

Were ALH84001 to be seen one day as compelling evidence for ancient life on Mars, two conclusions could be drawn. The first is that the origin of life is relatively easy, having happened independently on two planets in our solar system in a relatively short time during the solar system's early history. The second is that the sudden appearance of life, though still possibly a somewhat improbable event, first occurred on
either
Mars or Earth and was then transported in rocks, blasted off one or the other planet's surface by asteroid impacts, to seed the other.
^†

Regardless of whether life exists on other planets, scientists are completely
convinced that the universe is rife with organic material. Outlandish theories like those of Hoyle and Wickramasinghe and the controversial nature of claims like those made about past meteorites have tended to obscure the fact that organic molecules are indeed present in outer space—and present in vast quantities. The possibility that the first organic molecules on Earth originated in space, even if it seems outlandish to most people, has become very real to the majority of scientists studying the origin of life.

In some ways, the very word “space” is misleading. The vast expanses of space are not empty, but filled with cosmic clouds of gas and dust. The collapse of some types of cosmic clouds is thought to give rise to the formation of solar systems throughout the universe. We now know that the clouds themselves are filled with organic molecules, some of which likely make their way to planetary surfaces. Before turning to ALH84001, David McKay had been part of the growing effort at NASA to find ways of studying the chemical makeup of cosmic dust.

NASA space missions like
Apollo
and
Viking
have focused on searching for organic compounds such as amino acids on other worlds, but some of the sturdiest proof of a universe abundant in such complicated organics may be meteorite samples already in NASA's possession. Compelling evidence was provided by a meteorite that fell near the town of Murchison, Australia, in September of 1969, just two months after the return of the
Apollo 11
astronauts. It proved to be one of the biggest meteorite finds in history, yielding several hundred pieces that varied in size from a few ounces to 113 pounds. One fragment punctured the roof of a farmer's hay shed.

By late 1969, NASA was well prepared to study the Murchison samples and ensure a minimum amount of terrestrial contamination, eliminating the problems that had plagued meteorite finds ever since Orgueil. The samples turned out to be filled with compounds crucial to biochemistry. To date, ninety-two distinct amino acids have been identified in the meteorite, only nineteen of which naturally occur on Earth. These represent the strongest pieces of evidence that the organic building blocks of life could have come from outer space. The failure of the
Apollo 11
mission to find
significant amounts of organic compounds on the moon and the wildly speculative theories of scientists like Fred Hoyle have masked the fact that most serious exobiologists remain quite confident that, at the very least, organic materials are abundant elsewhere in the solar system and that life on other worlds is entirely possible.

L
IKE SO MANY
earlier claims for life in space over the previous centuries, the sensational news of the ALH84001 findings was eventually met by almost as much skepticism from the scientific community as enthusiasm from the general public. The National Academy of Sciences formed an investigative panel. After two years of review, an article published in
Science
entitled “Requiem for Life on Mars? Support for Microbes Fades” conveyed an emerging scientific consensus that much more had been made of the proof of life in ALH84001 than the facts warranted. Most of the evidence painstakingly compiled by McKay and the other scientists involved—the carbonate minerals, the PAHs, and the magnetite grains—could plausibly be attributed to other, nonbiological origins.