Fire in the Sky

Cosmic Collisions, Killer Asteroids, and the Race to Defend Earth

Gordon L. Dillow

• Publisher: Scribner
• Year: 2019
• ISBN:
  9781501187766
• Topic: Physical Sciences
• Subtopic: Space Science

This "accessible and always entertaining" ( Booklist ) combination of history, pop science, and in-depth reporting offers a fascinating account of the asteroids that hit Earth long ago and those streaming toward us now, as well as how prepared we are against asteroid-caused catastrophe. One of these days, warns Gordon Dillow, the Earth will be hit by a comet or asteroid of potentially catastrophic size. The only question is when. In the meantime, we need to get much better at finding objects hurtling our way, and if they're large enough to penetrate the atmosphere without burning up, figure out what to do about them.We owe many of science's most important discoveries to the famed Meteor Crater, a mile-wide dimple on the Colorado Plateau created by an asteroid hit 50, 000 years ago. In his masterfully researched Fire in the Sky, Dillow unpacks what the Crater has to tell us. Prior to the early 1900s, the world believed that all craters—on the Earth and Moon—were formed by volcanic activity. Not so. The revelation that Meteor Crater and others like it were formed by impacts with space objects has led to a now accepted theory about what killed off the dinosaurs, and it has opened up a new field of asteroid observation that is brimming with urgency. Dillow looks at great asteroid hits of the past and modern-day asteroid hunters and defense planning experts, including America's first Planetary Defense Officer.Satellite sensors confirm that a Hiroshima-scale blast occurs in the atmosphere every year, and a smaller, one-kiloton blast every month. While Dillow makes clear that the objects above can be deadly, he consistently inspires awe with his descriptions of their size, makeup, and origins. Both a riveting work of popular science and a warning to not take for granted the space objects hurtling overhead, Fire in the Sky is, ultimately, a testament to our universe's celestial wonders.

CHAPTER 1

---

IMPACT!

It’s fifty thousand years ago, in the middle of a vast rolling plain near the future site of Flagstaff, Arizona. And high up in the sky, just on the edge of space, an asteroid half the size of a city block is hurtling toward this exact spot at 40,000 miles an hour.

For hundreds of millions of years this cold, jagged, half-million-ton piece of tumbling space metal has been orbiting around the Sun, staying in its own lane and not bothering anybody. But then some outside force—a collision with another asteroid, or some subtle gravitational nudge from another planet—sent it off on a new path, a new orbit. That orbit over time has conspired to place this speeding asteroid and our own speeding Earth in the exact same spot in space at precisely the same moment. And soon, very soon, this asteroid’s traveling days will be over.

Earth isn’t completely defenseless against this sort of attack from space. If this asteroid is actually going to hit the Earth’s surface intact, first it has a gauntlet to run. The asteroid has to make it through the atmosphere.

You wouldn’t think the atmosphere would pose much of a problem for a flying space boulder. After all, it’s just a layer of air, and a pretty thin layer to boot. Proportionally, Earth’s atmosphere is thinner than the skin of an apple. But air is like water. If you do a graceful swan dive off the low board at the pool the water provides a gentle cushion; but if you do a hundred-mile-an-hour belly-flop off the Golden Gate Bridge, it’s almost like hitting concrete.

Same thing with this asteroid. It’s a blunt object, with all the aerodynamic glide qualities of a blacksmith’s anvil, and it’s traveling twenty times faster than a rifle bullet. So when the asteroid hits the increasingly dense air of the atmosphere it gets some pushback. The air molecules in front of the asteroid can’t get out of its way fast enough, and so the air in its path is radically compressed and heated up. Within seconds, temperatures on the asteroid’s previously frigid surface reach three thousand degrees and more, lighting up both the asteroid and the wall of shock-compressed air in front of it in a brilliant incandescent glow, and leaving a fiery tail of bright light miles long. At the same time, the tremendous pressure causes pieces of the asteroid to break off and fall toward the Earth’s surface on their own.

If our asteroid was smaller, or if it was made of rock instead of metal, the heat and pressure would probably destroy it, making it burn up or blow up before it ever reached the ground. Every day Earth’s atmosphere easily destroys millions of incoming pieces of space debris, creating meteors that flash in the night sky. Most of those pieces of space debris are tiny, the size of a grain of sand, but even the bigger pieces usually fail to survive the atmospheric gauntlet. Our atmosphere wraps around the Earth like a thin sheet of Kevlar, protecting us from assaults by minor intruders from space—which is another reason we should probably take better care of it.

But this asteroid of fifty thousand years ago is no grain of sand, no minor intruder. This asteroid is 150 feet wide, and it’s made of sterner stuff than rock. It’s composed of almost pure nickel-iron, an incredibly heavy and strong alloy. A single cubic foot of it—about the size of a 50-pound block of ice—weighs almost as much as a Harley-Davidson Sportster, and there are a million cubic feet of nickel-iron in this asteroid. Earth’s atmosphere does its best, but completely destroying this asteroid is an impossible order. Nothing is going to stop this thing now. In just a few seconds it’s going to slam into the Earth’s surface like a giant cosmic cannonball.

But before that happens, let’s freeze the asteroid in mid-plummet—say, about twenty miles above the Earth’s surface—and take a look at what it’s about to hit.

Ground zero for the incoming asteroid is a patch of mile-high tableland in what is now known to geologists as the Colorado Plateau. The climate is wetter and cooler on this day than it will be in modern times, the land a little more lush. Juniper and piñon pine woodlands are interspersed with grass-covered savannahs, and the ground is riven with flash-flood gullies and small flowing streams.

There are no people here on this day. The best scientific evidence suggests that humans won’t arrive in North America for another thirty thousand years or so. Still, there is abundant animal life—and with one notable exception, much of the animal life would be familiar to us in modern times. There are beetles and sawflies and spiders, rattlesnakes and gopher snakes, pack rats, moles, and voles; in the air there are hawks and hummingbirds and swallows. The one notable exception is that on this day fifty thousand years ago the land is also populated with those large—in some cases magnificently large—and now extinct Late Pleistocene animals collectively known as megafauna.

One of them is a species of elephant-like mammoth known as Mammuthus columbi—named for no particularly good reason after Christopher Columbus—a 13-foot-tall, 20,000-pound giant that grazes in matriarchal family groups in the grassy open meadowlands. Another is a species of mastodon, a slightly smaller distant cousin of the mammoth that browses on coniferous twigs in the forests. There are ten-foot-long giant ground sloths in the area, as well as an ancient type of camel appropriately known as Camelops hesternus—Latin for “Yesterday’s camel.” There are herds of horses and bison grazing and galloping on the plains, but the horses are smaller than modern-day horses, and the bison are bigger than the American buffalo of later eras—much bigger, with enormous horns that measure eight feet from tip to tip. There are predators lurking about as well—packs of fearsome dire wolves, and saber-toothed big cats known as Smilodons. In the air, soaring on the thermals, there are giant condor-like birds with wingspans of 16 feet.

Mammoths and mastodons, pack rats and rattlesnakes, sloths and swallows and Smilodons—these are what are waiting for the asteroid now poised above their heads. Mercifully, the creatures in the impact zone have no idea what’s coming. They can’t hear the sonic boom the asteroid creates as it bursts through the atmosphere, because the asteroid travels faster than the sound it makes. And if they happen to look up at the northwestern sky, all they see is a bright glow, with no indication that this blazing rock is coming directly at them. So there is no sense of impending doom, no panic, no stampeding terror.

Well, it would be nice if this peaceful, bucolic Late Pleistocene scene could continue. But since it can’t, we might as well get it over with. So now we go back up and unfreeze our plummeting asteroid—and two seconds later it hits the Earth with the force of a thousand Hiroshimas.

The impact isn’t an explosion in the conventional sense. Instead, the destructive force comes from kinetic energy. Every moving object—a car on a freeway, a cue ball on a pool table, an asteroid hurtling through space—possesses kinetic energy, and the heavier the object is and the faster it’s going, the more kinetic energy it has. As you can imagine, an asteroid that weighs hundreds of thousands of tons and is traveling at ten miles per second possesses an enormous amount of kinetic energy—and when it hits something it releases that energy with explosive force. To quantify that force, as a kind of shorthand scientists compare it to the energy released by a ton of TNT. The Hiroshima atomic bomb had the energy equivalent of about twelve thousand tons of exploding TNT. When our asteroid hits the ground, it releases the energy equivalent of some twelve million tons of TNT, or twelve megatons.

So even though the asteroid isn’t a bomb, it might as well be. The impact shatters rocks a thousand feet below the surface and pulverizes millions of tons of stone into a fine, talc-like powder. The explosion peels up thick layers of ancient limestone and sandstone and folds them back on themselves, like a firecracker going off inside a stack of pancakes. It ejects almost two hundred million tons of rock into the air, hurling boulders the size of small houses hundreds of yards, and sending smaller pieces arcing upward in thousands of smoking contrails. A giant fireball starts rising into the sky, searing everything around it and creating a dusty brown mushroom cloud that reaches up to the stratosphere.

Obviously, any living thing in the asteroid’s immediate point of impact—every tree, every bug, every Smilodon and Camelops—is instantly reduced to the molecular level. And those creatures are the lucky ones; they never know what hit them. Other animals farther from the impact point are less fortunate.

The asteroid’s impact sends a shock wave radiating out in every direction, a burst of overpressure that causes internal organs to collapse and eardrums to burst and blood to bubble in veins. That’s accompanied by a blast of wind moving in excess of 1,200 miles per hour—an atmospheric disturbance for which the word “wind” hardly seems adequate. This super-wind uproots trees, scours the ground bare of vegetation and sends everything in its path hurtling through the air in a maelstrom of debris—boulders, pebbles, jagged shafts of broken tree trunks, dead or dying rattlesnakes, pack rats, giant sloths. Twenty-thousand-pound mammoths are sent skittering along the ground like tumbleweeds.

Within three miles of the impact site, no living creature on the ground survives. Farther out the effects start to diminish, but even ten miles away the blast still hits with hurricane force, pelting victims with rocks and small debris and shredding their hides like a sandblaster. As if that weren’t bad enough, for miles around the ground is bombarded by falling chunks of the asteroid that sloughed off in the atmosphere, and by millions of pieces of molten nickel-iron and other materials that were thrown up by the impact and are now falling back to the ground. It’s a lethal rain of rock and iron.

And then, within just a few minutes, it’s over, the only sound the whimpers and bellows of the wounded. What’s left is a 300-square-mile patch of ground that has been scorched and stripped bare. And at the center there’s a blackened, smoldering, bowl-shaped hole in the earth, a crater almost a mile across and 700 feet deep, surrounded by a rim of displaced rock some twelve stories high.

It’s an astonishing amount of destruction. And yet, there’s something about this asteroid you should know. You should know that in the cosmic scheme of things, our asteroid’s violent collision with the Earth on this day fifty thousand years ago really isn’t any big deal. It’s not even all that unusual. The fact is that over the course of four and a half billion years, Earth has been hit millions of times by asteroids and comets as big as or bigger than this one—in some cases many orders of magnitude bigger. Earth has been bombarded by hurtling space bodies the size of mountains and even small planets, with collisions so powerful they tilted the Earth on its axis, sent huge chunks of Earth’s surface flying into space and enveloped the globe in shrouds of fire and dust that wiped out most of its species.

Our relatively small asteroid has done none of those things. As tough as it’s been for a few mastodons and giant sloths in the impact zone, other creatures grazing thirty miles away survive the asteroid’s impact quite nicely; it doesn’t even ruin their day. Within a few years, the blackened ground around the asteroid crater will be covered with new vegetation, and the animals will return. Except for the huge hole left in the ground, it will be almost as if it never even happened.

The bottom line is that by Earth-impacting-asteroid standards, our little asteroid of fifty thousand years ago has actually been something of a runt, a piddler, a weak sister.

So why do we care about this particular asteroid? What makes it so special?

The answer is simple. It’s because someday—in about forty-nine thousand and nine hundred years, to be more precise—this little asteroid and the crater it has left behind will become the most important of their kind in the history of science.

They’re going to change everything.

The crater is still there today. Officially it’s called Meteor Crater—which, as we’ll see, is a gross misnomer on several levels—and finding it is easy. Just head east or west on Interstate 40.

Westbound on I-40 from the New Mexico–Arizona border, the freeway traces the path of the old and fabled Route 66, the famous “Mother Road” that was an important part of American culture until it was strangled and mostly buried by the Interstate Highway System. The route passes through some of the most rugged and most beautiful country in the American Southwest. There are the magnificent badlands of the Painted Desert, so named by conquistadors under Francisco Coronado for the soaring buttes and mesas layered up in brilliant bands of lavender and vermillion and magenta; the vistas look like sunsets rendered in rock. The highway also transects the Petrified Forest National Park, a Mars-scape where fallen stands of giant pine trees more than two hundred million years old have been literally turned to stone—smoky quartz, purple amethyst, yellow citrine. The Petrified Forest is an eerie place, a haunt for ghosts.

There aren’t any cities out this way, and the few towns along the route tend to be low-slung and dusty. Farther west on I-40 there’s the small ranching and railroad community of Holbrook, which not so very long ago had its own brush with bombardment from space. In 1912 a space boulder about the size of an ice chest exploded high in the air east of town, pelting the ground below with thousands upon thousands of pea-sized meteorites—an event that was known as “the day it rained rocks.” Or at least it used to be known that way. When I ask the waitress at a coffee shop about the meteorite fall, she’s never heard of it. Oh? And has she lived here long? All my life, she says—which is another thing about assaults from space. We tend to forget them pretty quickly.

Still farther westward there’s Winslow, a once-bustling Route 66 town now fallen on leaner times. If the name is familiar it’s probably because of the line from the 1972 Eagles hit song, “Take It Easy”: Well I’m a standin’ on a corner in Winslow, Arizona. . . . That’s just about the only thing Winslow is famous for. In fact, after the interstate bypassed the city center in the late 1970s, the Winslow town fathers tried to revive their downtown’s flagging fortunes by building the Standin’ on the Corner municipal park, complete with a flatbed Ford and a bronze statue of the late Eagles lead singer Glenn Frey. The effort has been a modest success. Every year tens of thousands of travelers, most of them graying Boomers, stop by to take selfies with the statue and browse in the nearby gift shop, where the sound system plays Eagles’ songs—and nothing but Eagles’ songs—all day long. “You get to where you don’t even hear it anymore,” a weary clerk tells me.

North of town I-40 continues west, straight as a rifle shot, through a vast expanse of high desert (elevation about 5,500 feet). This is not the woodland-savannah of fifty thousand years ago; sadly, there are no grazing mammoths or herds of galloping giant bison. A few stunted junipers struggle to survive in the washes, but other than that a guy could go blind looking for a tree. Broiling in the summer, frigid in winter, 20- and 30-mile-an-hour winds are a constant, and gusts of more than 100 miles per hour have been recorded. On the highway, 80,000-pound big rigs shimmy and sway in the crosswind; passing them can be an experience. Except for the highway and the Burlington Northern and Santa Fe train tracks and the occasional billboard touting tourist attractions that lie ahead—“Jewelry Made By Indians!” “Moccasins For the Whole Family!”—there is simply nothing here. It’s the exact geographic center of the lonesome heart of nowhere. People who enjoy desolate places might find a stark minimalist beauty in it. Those who don’t might just want to step on the gas.

Eastbound, the trip to Meteor Crater is a little more scenic, at least at first. First there’s Flagstaff, an attractive mountain town of some seventy thousand souls that bills itself as the gateway to the Grand Canyon eighty miles north. Flagstaff is home to Northern Arizona University and the century-plus-old Lowell Observatory, a piney, campus-like facility that was the nerve center for countless space discoveries—including the discovery of thousands of fresh new asteroids, some of which could someday come our way. I’ll get back to Lowell Observatory later.

East on I-40 there are mountains covered with stately Ponderosa pines, then rolling hills with copses of piñon pine. Twenty miles out from Flagstaff there’s Winona, another old Route 66 small town best known for its brief mention in a popular song—in this case, the 1946 Nat King Cole hit, “(Get Your Kicks on) Route 66.” Flagstaff, Arizona / Don’t forget Winona, the song says, and when I repeat the lyric to the old-timer behind the counter at the gas station/convenience store he smiles and gives me a free “Don’t Forget Winona” postcard. Farther along eastbound, back in the high desert now, on the right are the crumbled remains of a famous 1940s Route 66 tourist trap called the Twin Arrows Trading Post—the “arrows” being two telephone poles stuck at an angle in the ground with plywood sheets for fletchings. The arrows are still there, but the trading post name has since been appropriated by the nearby Twin Arrows Native American casino, where the Navajo Nation exacts its long overdue revenge. Although it’s not visible from the highway, still farther on are the equally dissolute remains of an Old West ghost town called Canyon Diablo, which will play a role later in our story.

But whichever route taken, westbound or eastbound, eventually there is Exit 233. I steer my pickup onto the exit ramp, past the Meteor Mobil station and the Meteor RV Park, and then head south on a two-lane stretch of good blacktop. As signs along the road announce, I’m crossing part of the famous Bar T Bar Ranch, a family-owned spread of 300,000 acres of private and leased land that prides itself on raising range-fed, antibiotic- and growth-hormone-free Angus cattle. (If you’d like to eat one, you can do so at the upscale Diablo Burger restaurants in Flagstaff and Tucson.) The ground around here is still littered with small fragments of meteorite material left by our asteroid of fifty...

Table of contents

• Cover
• Dedication
• Introduction
• Chapter 1: Impact!
• Chapter 2: Miraculous Apparitions in the Ayre
• Chapter 3: Asteroid Miners
• Chapter 4: Star Wounds
• Chapter 5: T-Rex with a String of Pearls
• Chapter 6: Asteroid Hunters
• Chapter 7: Planetary Defense
• Chapter 8: Asteroid Killers
• Chapter 9: Asteroid Wars
• Epilogue
• Photographs
• Acknowledgments
• About the Author
• Chapter Notes, Sources, and Relevant Fun Facts
• Index
• Copyright