Asteroid Threat : Defending Our Planet from Deadly Near-earth Objects (9781616149147) (4 page)

And, Gene Shoemaker added, the next time a really big asteroid or comet strikes the home planet, “It will produce a catastrophe that exceeds all the other catastrophes by a large measure. These things have hit the Earth in the past. They will hit Earth in the future,” he added, matter-of-factly. A rock that is more than a kilometer in diameter would create an explosion on impact equivalent to all the world's nuclear weapons going off at the same instant, he said. “Actually,” he corrected, “it would be a little bit more energy than that.” The eruption of Earth and everything on it would fill the sky with so much debris that it would darken the world for months. It would cause “mass hysteria,” Carolyn added.
⁸

David H. Levy, a prolific and ubiquitous Canadian with widely varying interests who claims to be “one of the most successful comet discoverers in history” (he spotted eight of them using telescopes in his backyard, according to his resume) is a longtime friend of the Shoemakers who appeared with them on that National Geographic special. He drew a vivid analogy in describing how a human would feel if he or she were near an impact explosion like the one that caused the crater in which Nordling was built. “You would feel as though you were in an oven turned to broil,” he said.
⁹

The most momentous time in Levy's and the Shoemakers' lives began on March 25, 1993, when Carolyn spotted what looked like a “squashed comet” in a photograph of the space around Jupiter they had taken as part of their routine photos two days earlier at the Mount Palomar Observatory in California.
They were perplexed because, instead of a nucleus trailing a long tail, which is what comets are supposed to look like, this one was bar shaped and seemed to have a series of little tails. Close analysis of the picture under a microscope showed that the “bar” was in fact a string of twenty or twenty-one cometary fragments—a formation of them—bearing down on the giant planet in what was a near-certain collision course. They quickly alerted the astronomical community, and from July 16 to 22, 1994, the three of them and the rest of the world were treated to the first look humans have ever had of a collision between a planet and its cosmic attackers. They watched, almost in disbelief, as the huge chunks of ice successively plowed into Jupiter at a velocity they estimated to be sixty kilometers a second. The largest of the impactors was calculated to be two kilometers in diameter. Each strike left intensely hot gas bubbles and large, dark scars in Jupiter's atmosphere that remained for months. Plumes of gas thousands of kilometers high shot into the atmosphere. It was the first—and so far the only—time when humans have actually gotten to witness an attack on a planet. Levy has written about it, starting with the first of the historic impacts:

The crash of fragment A was an extraordinary event all by itself. That was the first time that people had witnessed such a collision. Had A been the only impact, we would have rejoiced and studied its effects for years. But in the opera of impact week, A was just the overture. One of the smallest nuclei, A was hitting the planet at a place farther away from Jupiter's daylight side than any of the others, so few scientists—Gene Shoemaker was one—expected to see the plume of material thrown into the atmosphere by its strike.
¹⁰

The opera Levy may have had in mind was Gian Carlo Menotti's
Amahl and the Night Visitors
, whose young hero tells his mother that there is a colossal star over their house, but he is not believed. One after another, the long line of flying icebergs struck Jupiter, each time causing a huge explosion and a gas plume.

What happened next as the astronomers and other scientists watched on monitors the successive impacts belied the widely held belief that science is basically dull and so are its practitioners. “For a moment the group of scientists just sat there, stunned,” Levy later reported. “There was a collective gasp. It took a few more seconds before the scientists began to realize what a treasure they had, that in this one picture, all the months of planning had paid off handsomely. ‘Oh,' Heidi Hammel exclaimed. ‘My God!'”

Levy remarked, “The whole picture was clear now, and the room erupted with cheering and applause. ‘We realized that we had something truly spectacular on our hands,' Hal Weaver continued. ‘Melissa McGrath ran upstairs to get the champagne that she had bought for the occasion (even though she is the first to admit that she hadn't really expected to see anything like this), and Heidi Hammel popped the cork.'”
¹¹

New York Times
journalist William J. Broad reported, “The Chicken Little crowd, which once drew smiles by suggesting that Earth could be devastated by killer rocks from outer space is suddenly finding its warnings and agenda taken seriously now that Jupiter has taken a beating in recorded history's biggest show of cosmic violence.” The story's headline made the point explicitly and accurately: “When Worlds Collide: A Threat to the Earth Is a Joke No Longer.”
¹²

As is true in most other (pardon) groundbreaking work, the hunt for large, potentially dangerous rocks that have profoundly affected Earth or that could threaten it, perhaps catastrophically, has attracted a variety of people with widely varying opinions.

George Darwin, whose father, Charles, wrote
On the Origin of Species
, one of the towering works of science, was understandably interested in origins, too; though he was interested in the Moon's origins, not
homo sapiens
'. In 1878 he came to the conclusion that the Moon was probably flung off Earth when
the planet was mostly liquid and rotating; that is, the two bodies had simply come apart and gone their separate ways. The theory quickly gained popularity not only in the scientific community but also among the general public, where the ancient romantic myth about the Earth goddess giving birth to the Moon goddess was happily resurrected and cherished. Four years later, a geologist named Osmond Fisher embellished the theory when he announced that the Pacific Basin was the birth scar, or depression, that resulted when the Moon separated from her—
her
—mother.
¹³
If true, it would undoubtedly have been the worst case of a postpartum depression in the history of this world.
¹⁴
But no evidence to support that kind of event has ever turned up.

Then there was Thomas Jefferson Jackson See, a supremely fatuous, unscrupulous, arrogant, self-promoting, altogether implausible character whose otherwise credible research and discoveries were almost entirely eclipsed by his blatantly incorrect, but stubbornly held, belief. He was adamant that the Moon was really a full-fledged planet in its own right that came from a place very far away and happened to be passing Earth when it was pulled in by this planet's more powerful gravitational field and was thus forced into a permanent orbit.

See was born in Missouri in mid-February 1866, studied astronomy at the University of Berlin, and, appropriately, died on the Fourth of July, 1962.

He was one of science's most memorable and enigmatic characters: a professional astronomer with a colossally inflated ego who had the manner of a colorful vaudevillian like the ones performing seemingly wondrous feats on stages in music halls while he was doing about the same thing in observatories. See's contributions to astronomy, and to the study of binary stars in particular, were widely recognized and eventually won him mention in the
Encyclopedia Britannica
.
¹⁵

But T. J. J. See was the polar opposite of the popular image of the quiet, self-effacing scientist who puts long, lonely hours of
research and discovery above blatantly obvious self-promotion. (That is not to say reputable scientists do not promote themselves. They certainly do. But it is customarily done with apparent modesty and at least the veneer of discretion.) Not so with See. He reveled in the kind of personal and professional self-absorption, bombast, and arrogance that brought scorn and contempt from the staid and usually understated astronomical community. He landed his first job in George Ellery Hale's prestigious department at the University of Chicago, where he was judged not fit for promotion by the distinguished astronomer and was therefore effectively forced to leave. His next stop was the Lowell Observatory at Flagstaff, Arizona, another top-notch institution. But he treated the staff with undisguised contempt for being mere underlings—in effect, his professional servants—and they reacted the way others in their predicament very often do; they found quiet but effective ways to slow their work to the point at which it impeded the astronomy. His departure was therefore inevitable. See's next stop, in 1898, was the US Naval Observatory in Washington, DC, where his carelessness and by then renowned egocentricity again caused angst.

See published
Researches on the Evolution of the Stellar Systems, Vol. II, The Capture Theory of Cosmical Evolution
, a book that ran to more than seven hundred pages and was therefore physically, as well as intellectually, very weighty. In it, he argued that space is not and never was a vacuum. Rather, it was filled with a tangible “resisting medium” that slowed the approaching Moon—which, he pointed out, could not have happened in a vacuum—until, after a great deal of time had passed, it was moving slowly enough to be captured by Earth and pulled into a permanent orbit around the planet. Furthermore, he added, all the planets in the Solar System had been captured by the Sun in precisely the same way. The resisting medium, See explained, was as fundamental to celestial mechanics as Newton's law of gravity.
¹⁶

That the theory was wrong was bad enough. But it was also tainted by a blatant meanness. He described his task, for example, as being necessary to “brush aside the erroneous doctrines heretofore current, as one would the accumulated dust and cobwebs of ages.”
¹⁷
That gratuitously malicious jab almost undoubtedly left many of his fellow astronomers muttering angry retorts to themselves and their colleagues.

Three years later, in 1913, newspaper publisher and amateur astronomer William Larkin Webb published a saccharine biography of See that once again confounded the astronomical community.
Brief Biography and Popular Account of the Unparalleled Discoveries of T. J. J. See
, as it was called, mirrored his grossly inflated ego. As would be expected, it was swollen with adoring hyperbole. Given See's nature, it was understandable that a rumor quickly started circulating that the self-created superstar of the stars had in fact written it himself.

A reviewer for the
Nation
was so put off by the book's blatant infatuation with its subject—a tone that in other circumstances has been likened to drowning in warm honey—that he or she in effect held up a mirror: “The infant See, we are told, first saw the light on the 393d anniversary of Copernicus's birth…[and] showed himself ‘every inch a natural philosopher' by speculating on the origins of the sun, moon and stars at the tender age of two, never so much as dreaming that he should grow into a little boy with ‘methodical methods,' and one day become ‘the greatest astronomer in the world.'”
¹⁸
Meanwhile, to his eternal discredit, See also called Albert Einstein a fraud and a plagiarist. Einstein would not lend credence to See by responding, choosing not to sling the mud back and maintaining a dignified silence that added to his stature.
¹⁹

Harold C. Urey, the brilliant, acid-tongued chemist who won the Nobel Prize in 1934 for discovering deuterium, also believed that the Moon was captured by Earth. It was therefore not inherently a satellite of this planet, he reasoned, but
rather the fifth of the inner planets that included Mars or the tenth, if the group extended out to Pluto. The latter was eventually demoted to a mere “planetoid” or “dwarf planet” by the International Astronomical Union after astrophysicist Neil deGrasse Tyson, the irrepressibly enthusiastic and animated head of New York's Hayden Planetarium, called for its status to be lowered. He was promptly deluged with hate mail from irate grade-schoolers who identified the newly downgraded (and therefore insulted) member of the Solar System with Walt Disney's beloved pooch of the same name.

So there it was: Darwin the Younger's “fission” theory had it that Earth and its Moon were once a single entity that had come apart on its own in a cosmic split or divorce. See's and Urey's “capture” hypothesis argued that the Moon had once been going its own way but was snagged by Earth and pulled into a permanent embrace. And finally, there was a “coaccretion” theory that maintained both Earth and the Moon were simply created independently when everything else was.
²⁰
The theories were of course considered eminently plausible by their adherents, all of whom believed that theirs was undoubtedly the most likely to have occurred. Collectively, the three explanations seemed to cover all the possibilities.

But nowhere, at least in the astronomical big leagues, was there mention of the fact that the Moon could have been formed when a planet-sized wanderer smashed into Earth with such force that it knocked off a large piece of it, which, over millennia, gradually turned from a jagged chunk of soil, rock, and minerals into a sphere like the other moons and then began circling its “mother.” It wasn't until well into the twentieth century that the true level of violence in the universe began to be seen and understood. It was nothing short of phenomenal. As telescopes improved, whole galaxies could be seen to collide, and the Moon's craters, which had been caused far more by impacts than by volcanoes, offered stark proof that Earthlings (and
who knew, maybe Martians, too) live in a universe where violence and destruction occur constantly and are so massive that they are literally unimaginable (“mind-boggling,” the overused cliché, is appropriate). The mystery of how the Moon came to be was finally solved when teams of geologists and geophysicists, working independently but with access to some of each other's research, discovered why the dinosaurs disappeared.