Asteroids Among Us
Our solar system swirls with some 625,000 cataloged asteroids and comets, plus innumerable smaller rocks. And every once in a while a big one crashes to Earth. Arizona’s 3,900-foot-wide Meteor Crater was produced around 50,000 years ago by an iron-and-nickel chunk about 165 feet across. A similar disaster, science fiction writer Arthur C. Clarke warned, “might not occur again for a thousand years—but it might occur tomorrow.”
French writer Antoine de Saint-Exupéry called on his experience as an aviator when he wrote The Little Prince, whose narrator crash-lands in the Sahara. While the pilot repairs his airplane, he encounters a “most extraordinary small person” from a planet “scarcely any larger than a house.” The pilot surmises that the extraterrestrial visitor hails from Asteroid B-612 and that for his interplanetary travels “he took advantage of the migration of a flock of wild birds.”
Because it’s so close, the prince’s asteroid qualifies as a near-Earth object (NEO), a designation that also includes comets and other entities in our planet’s proximity. Asteroids (the word derives from the Greek for “starlike”)—or minor planets, as astronomers call them—are small chunks of debris left over from the formation of the solar system. Most of the estimated 625,000 minor planets so far identified reside in the asteroid belt, an orbital path between Mars and Jupiter. Some are “potentially hazardous asteroids”: those with a minimum diameter of 500 feet that come within 5 billion miles of Earth. The International Astronomical Union’s Minor Planet Center keeps track of verified NEO discoveries. The current tally tops 10,000 (increasing by about 1,000 a year), including 1,426 PHAs.
“I have serious reason to believe,” writes the narrator of The Little Prince, “that the planet from which the little prince came is the asteroid known as B-612. This asteroid has only once been seen through the telescope…in 1909.” Such elusiveness is common to near-Earth objects, due to their small sizes, low albedo (i.e., reflectivity) and unknown orbital paths, and this makes them potentially dangerous to our planet. Interplanetary debris enters Earth’s atmosphere constantly, mostly as rocks and dust. Occasionally, a chunk big enough to cause damage comes through. The meteor that exploded over Chelyabinsk, Russia, in February 2013 was about 60 feet across. The object that crashed into the Gulf of Mexico 66 million years ago and created conditions that led to the extinction of the dinosaurs may have been an asteroid six miles wide.
The B612 Foundation, a planetary defense mission named after the prince’s asteroid, has established that we have the technology to deflect an asteroid headed for Earth, but the initiative must begin decades before any projected impact. This means locating potentially troublesome near-Earth objects—ones whose paths intersect with our orbit—is paramount. The foundation’s website reminds us, “The dinosaurs didn’t have a space program.”
Most of the thousands of interplanetary fragments that bombard our atmosphere every day are small and burn up without notice. But larger near-Earth objects, known and unknown, are never far away. In February 2013 a meteor exploded 14 miles above Chelyabinsk, Russia, and—just 16 hours later—a 100-foot-diameter asteroid made a close pass, only 17,000 miles away. The second of these was predicted; the first, uncharted and hidden in the sun’s glare, was not.
The Cretaceous–Paleogene boundary is a geologic layer that marks the end of the Mesozoic era as well as a mass extinction of life on Earth. The rock in this layer is unusually rich in iridium, an element rarely found on our planet’s surface but common in space debris. When scientists examined the 100-mile-wide Chicxulub Crater buried under Mexico’s Yucatan Peninsula, they found definitive proof that a space object had slammed into Earth’s crust. The resulting explosion triggered earthquakes, volcanic eruptions and tsunamis, leading to rapid changes in atmospheric conditions and climate that blocked sunlight, thwarted photosynthesis and eventually wiped out most of the dinosaurs and many other life forms. A 2013 study suggests the impact of a high-velocity comet may have produced the crater.
The biggest near-Earth object strike in modern times was 1908’s Tunguska event, probably caused by a 150-foot-wide asteroid that shot across the skies of Siberia. The impact site—an 830-square-mile area with about 80 million downed trees—was so remote it wasn’t discovered for years. Nonetheless, witnesses of the spectacularly bright, thundering star thought it signaled the end of the world.
Astronomical events are often interpreted as divine communications. The 1833 Leonid meteor shower, yielding an estimated 200,000 shooting stars per hour, was taken as a sign by Independence, Missouri, citizens to drive out the town’s Mormon settlers. (A century later the shower’s lore inspired the jazz standard “Stars Fell on Alabama.”) The book of Genesis declares, “The Lord rained on Sodom and Gomorrah sulfur and fire…out of heaven,” destroying the ancient sin cities. But in A Sumerian Observation of the Köfels’ Impact Event (2008), Alan Bond and Mark Hempsell, whose research centers on an ancient stone tablet, argue that the biblical “fire and brimstone” was caused by a half-mile-wide asteroid that crashed into central Europe in 3123 B.C. They also claim the impact killed Otzi the Iceman, a 5,000-year-old mummified Bronze Age hunter found frozen in the Austrian Alps.
Science fiction writer and inventor Arthur C. Clarke was among those who believed Sodom and Gomorrah might have been “meteor casualties.” In his 1972 novel Rendezvous With Rama, a meteor crash that destroys the storied cities of northern Italy prompts a planetary defense program, Project Spaceguard. Clarke issued a decidedly nonfictional alert when Comet Shoemaker-Levy plunged into Jupiter in 1994, urging development of the “technology necessary to ward off, or even destroy, such intruders from outer space.”
Disaster from above is a sci-fi mainstay, exploited in literary works (and their movie spin-offs) ranging from When Worlds Collide (1933) and The Andromeda Strain (1969) to the Christian apocalyptic Left Behind series. Usually, as in the 1998 rival space disaster films Deep Impact (comet) and Armageddon (asteroid), humanity is saved. But measures taken to deflect an approaching asteroid fall short in Seeking a Friend for the End of the World. As a newscaster explains, “The final mission to save mankind has failed. The 70-mile-wide asteroid known commonly as Matilda is set to collide with Earth in exactly three weeks’ time, and we’ll be bringing you up-to-the-minute coverage of our countdown to the End of Days, along with all your classic rock favorites.”
Late in the Cretaceous period, the impact of an enormous space object altered Earth’s geologic and atmospheric conditions. The dinosaurs never knew what hit them. The environment that had sustained the ancient creatures was quickly transformed, and they were unable to adapt. Several recent disaster movies of mixed acclaim have pondered the survival of our own species. Seeking a Friend for the End of the World is both feel-good and feel-bad comedy, both love story and space disaster movie. Once the end is clearly nigh, some characters indulge in sex, drugs or violence, while others turn to love. Lars von Triers’s Melancholia (2011) just goes for the bad feelings (and bad science), as a previously unknown giant planet heads for a collision with Earth. Meanwhile, Abel Ferrara’s 4:44 Last Day on Earth (2011) highlights the banality of human life. The 2013 farce This Is the End concentrates on callow young celebrities coping with the Christian rapture, while that year’s British analog, The World’s End, focuses on middle-aged men. Take Shelter (2011), Michael Shannon’s moving portrayal of a man preparing for a catastrophe that may be entirely in his head, trumps them all in its wrenching account of an end-time.