A
field assistant, Rudy Pascucci, left, and the paleontologist Robert
DePalma, right, at DePalma’s dig site. Of his discovery, DePalma said,
“It’s like finding the Holy Grail clutched in the bony fingers of Jimmy
Hoffa, sitting on top of the Lost Ark.”
Photograph by Richard Barnes for The New Yorker
If,
on a certain evening about sixty-six million years ago, you had stood
somewhere in North America and looked up at the sky, you would have soon
made out what appeared to be a star. If you watched for an hour or two,
the star would have seemed to grow in brightness, although it barely
moved. That’s because it was not a star but an asteroid, and it was
headed directly for Earth at about forty-five thousand miles an hour.
Sixty hours later, the asteroid hit. The air in front was compressed and
violently heated, and it blasted a hole through the atmosphere,
generating a supersonic shock wave. The asteroid struck a shallow sea
where the Yucatán peninsula is today. In that moment, the Cretaceous
period ended and the Paleogene period began.
A few years ago,
scientists at Los Alamos National Laboratory used what was then one of
the world’s most powerful computers, the so-called Q Machine, to model
the effects of the impact. The result was a slow-motion,
second-by-second false-color video of the event. Within two minutes of
slamming into Earth, the asteroid, which was at least six miles wide,
had gouged a crater about eighteen miles deep and lofted twenty-five
trillion metric tons of debris into the atmosphere. Picture the splash
of a pebble falling into pond water, but on a planetary scale. When
Earth’s crust rebounded, a peak higher than Mt. Everest briefly rose up.
The energy released was more than that of a billion Hiroshima bombs,
but the blast looked nothing like a nuclear explosion, with its
signature mushroom cloud. Instead, the initial blowout formed a “rooster
tail,” a gigantic jet of molten material, which exited the atmosphere,
some of it fanning out over North America. Much of the material was
several times hotter than the surface of the sun, and it set fire to
everything within a thousand miles. In addition, an inverted cone of
liquefied, superheated rock rose, spread outward as countless red-hot
blobs of glass, called tektites, and blanketed the Western Hemisphere.
Some
of the ejecta escaped Earth’s gravitational pull and went into
irregular orbits around the sun. Over millions of years, bits of it
found their way to other planets and moons in the solar system. Mars was
eventually strewn with the debris—just as pieces of Mars, knocked aloft
by ancient asteroid impacts, have been found on Earth. A 2013 study in
the journal Astrobiology estimated that tens of
thousands of pounds of impact rubble may have landed on Titan, a moon of
Saturn, and on Europa and Callisto, which orbit Jupiter—three
satellites that scientists believe may have promising habitats for life.
Mathematical models indicate that at least some of this vagabond debris
still harbored living microbes. The asteroid may have sown life
throughout the solar system, even as it ravaged life on Earth.
The
asteroid was vaporized on impact. Its substance, mingling with
vaporized Earth rock, formed a fiery plume, which reached halfway to the
moon before collapsing in a pillar of incandescent dust. Computer
models suggest that the atmosphere within fifteen hundred miles of
ground zero became red hot from the debris storm, triggering gigantic
forest fires. As the Earth rotated, the airborne material converged at
the opposite side of the planet, where it fell and set fire to the
entire Indian subcontinent. Measurements of the layer of ash and soot
that eventually coated the Earth indicate that fires consumed about
seventy per cent of the world’s forests. Meanwhile, giant tsunamis
resulting from the impact churned across the Gulf of Mexico, tearing up
coastlines, sometimes peeling up hundreds of feet of rock, pushing
debris inland and then sucking it back out into deep water, leaving
jumbled deposits that oilmen sometimes encounter in the course of
deep-sea drilling.
The damage had only begun. Scientists still
debate many of the details, which are derived from the computer models,
and from field studies of the debris layer, knowledge of extinction
rates, fossils and microfossils, and many other clues. But the over-all
view is consistently grim. The dust and soot from the impact and the
conflagrations prevented all sunlight from reaching the planet’s surface
for months. Photosynthesis all but stopped, killing most of the plant
life, extinguishing the phytoplankton in the oceans, and causing the
amount of oxygen in the atmosphere to plummet. After the fires died
down, Earth plunged into a period of cold, perhaps even a deep freeze.
Earth’s two essential food chains, in the sea and on land, collapsed.
About seventy-five per cent of all species went extinct. More than
99.9999 per cent of all living organisms on Earth died, and the carbon
cycle came to a halt.
Earth
itself became toxic. When the asteroid struck, it vaporized layers of
limestone, releasing into the atmosphere a trillion tons of carbon
dioxide, ten billion tons of methane, and a billion tons of carbon
monoxide; all three are powerful greenhouse gases. The impact also
vaporized anhydrite rock, which blasted ten trillion tons of sulfur
compounds aloft. The sulfur combined with water to form sulfuric acid,
which then fell as an acid rain that may have been potent enough to
strip the leaves from any surviving plants and to leach the nutrients
from the soil.
Today, the layer of debris, ash, and soot deposited by the asteroid strike is preserved in the Earth’s sediment as
a stripe of black about the thickness of a notebook. This is called the
KT boundary, because it marks the dividing line between the Cretaceous
period and the Tertiary period. (The Tertiary has been redefined as the
Paleogene, but the term “KT” persists.) Mysteries abound above and below
the KT layer. In the late Cretaceous, widespread volcanoes spewed vast
quantities of gas and dust into the atmosphere, and the air contained
far higher levels of carbon dioxide than the air that we breathe now.
The climate was tropical, and the planet was perhaps entirely free of
ice. Yet scientists know very little about the animals and plants that
were living at the time, and as a result they have been searching for
fossil deposits as close to the KT boundary as possible.
One
of the central mysteries of paleontology is the so-called “three-metre
problem.” In a century and a half of assiduous searching, almost no
dinosaur remains have been found in the layers three metres, or about
nine feet, below the KT boundary, a depth representing many thousands of
years. Consequently, numerous paleontologists have argued that the
dinosaurs were on the way to extinction long before the asteroid struck,
owing perhaps to the volcanic eruptions and climate change. Other
scientists have countered that the three-metre problem merely reflects
how hard it is to find fossils. Sooner or later, they’ve contended, a
scientist will discover dinosaurs much closer to the moment of
destruction.
Locked
in the KT boundary are the answers to our questions about one of the
most significant events in the history of life on the planet. If one
looks at the Earth as a kind of living organism, as many biologists do,
you could say that it was shot by a bullet and almost died. Deciphering
what happened on the day of destruction is crucial not only to solving
the three-metre problem but also to explaining our own genesis as a
species.
On
August 5, 2013, I received an e-mail from a graduate student named
Robert DePalma. I had never met DePalma, but we had corresponded on
paleontological matters for years, ever since he had read a novel I’d
written that centered on the discovery of a fossilized Tyrannosaurus rex
killed by the KT impact. “I have made an incredible and unprecedented
discovery,” he wrote me, from a truck stop in Bowman, North Dakota. “It
is extremely confidential and only three others know of it at the
moment, all of them close colleagues.” He went on, “It is far more
unique and far rarer than any simple dinosaur discovery. I would prefer
not outlining the details via e-mail, if possible.” He gave me his
cell-phone number and a time to call.
I called, and he told me
that he had discovered a site like the one I’d imagined in my novel,
which contained, among other things, direct victims of the catastrophe.
At first, I was skeptical. DePalma was a scientific nobody, a Ph.D.
candidate at the University of Kansas, and he said that he had found the
site with no institutional backing and no collaborators. I thought that
he was likely exaggerating, or that he might even be crazy.
(Paleontology has more than its share of unusual people.) But I was
intrigued enough to get on a plane to North Dakota to see for myself.
DePalma’s
find was in the Hell Creek geological formation, which outcrops in
parts of North Dakota, South Dakota, Montana, and Wyoming, and contains
some of the most storied dinosaur beds in the world. At the time of the
impact, the Hell Creek landscape consisted of steamy, subtropical
lowlands and floodplains along the shores of an inland sea. The land
teemed with life and the conditions were excellent for fossilization,
with seasonal floods and meandering rivers that rapidly buried dead
animals and plants.
Dinosaur hunters first discovered these rich
fossil beds in the late nineteenth century. In 1902, Barnum Brown, a
flamboyant dinosaur hunter who worked at the American Museum of Natural
History, in New York, found the first Tyrannosaurus rex here, causing a worldwide sensation. One paleontologist estimated that in the Cretaceous period Hell Creek was so thick with T. rexes that they were like hyenas on the Serengeti. It was also home to triceratops and duckbills.
DePalma’s
thesis adviser estimated that the site will keep specialists busy for
half a century. “Robert’s got so much stuff that’s unheard of,” he said.
“It will be in the textbooks.”
Photograph by Richard Barnes for The New Yorker
The
Hell Creek Formation spanned the Cretaceous and the Paleogene periods,
and paleontologists had known for at least half a century that an
extinction had occurred then, because dinosaurs were found below, but
never above, the KT layer. This was true not only in Hell Creek but all
over the world. For many years, scientists believed that the KT
extinction was no great mystery: over millions of years, volcanism,
climate change, and other events gradually killed off many forms of
life. But, in the late nineteen-seventies, a young geologist named
Walter Alvarez and his father, Luis Alvarez, a nuclear physicist,
discovered that the KT layer was laced with unusually high amounts of
the rare metal iridium, which, they hypothesized, was from the dusty
remains of an asteroid impact. In an article in Science,
published in 1980, they proposed that this impact was so large that it
triggered the mass extinction, and that the KT layer was the debris from
that event. Most paleontologists rejected the idea that a sudden,
random encounter with space junk had drastically altered the evolution
of life on Earth. But as the years
passed the evidence mounted, until, in a 1991 paper, the smoking gun was
announced: the discovery of an impact crater buried under thousands of
feet of sediment in the Yucatán peninsula, of exactly the right age, and
of the right size and geochemistry, to have caused a worldwide
cataclysm. The crater and the asteroid were named Chicxulub, after a
small Mayan town near the epicenter.
One of the authors of the
1991 paper, David Kring, was so frightened by what he learned of the
impact’s destructive nature that he became a leading voice in calling
for a system to identify and neutralize threatening asteroids. “There’s
no uncertainty to this statement: the Earth will be hit by a
Chicxulub-size asteroid again, unless we deflect it,” he told me. “Even a
three-hundred-metre rock would end world agriculture.”
In 2010, forty-one researchers in many scientific disciplines announced, in a landmark Science
article, that the issue should be considered settled: a huge asteroid
impact caused the extinction. But opposition to the idea remains
passionate. The main competing hypothesis is that the colossal “Deccan”
volcanic eruptions, in what would become India, spewed enough sulfur and
carbon dioxide into the atmosphere to cause a climatic shift. The
eruptions, which began before the KT impact and continued after it, were
among the biggest in Earth’s history, lasting hundreds of thousands of
years, and burying half a million square miles of the Earth’s surface a
mile deep in lava. The three-metre gap below the KT layer, proponents
argued, was evidence that the mass extinction was well under way by the
time of the asteroid strike.
In
2004, DePalma, at the time a twenty-two-year-old paleontology
undergraduate, began excavating a small site in the Hell Creek
Formation. The site had once been a pond, and the deposit consisted of
very thin layers of sediment. Normally, one geological layer might
represent thousands or millions of years. But DePalma was able to show
that each layer in the deposit had been laid down in a single big
rainstorm. “We could see when there were buds on the trees,” he told me.
“We could see when the cypresses were dropping their needles in the
fall. We could experience this in real time.” Peering at the layers was
like flipping through a paleo-history book that chronicled decades of
ecology in its silty pages. DePalma’s adviser, the late Larry Martin,
urged him to find a similar site, but one that had layers closer to the
KT boundary.
Today, DePalma, now thirty-seven, is still working
toward his Ph.D. He holds the unpaid position of curator of vertebrate
paleontology at the Palm Beach Museum of Natural History, a nascent and
struggling museum with no exhibition space. In 2012, while looking for a
new pond deposit, he heard that a private collector had stumbled upon
an unusual site on a cattle ranch near Bowman, North Dakota. (Much of
the Hell Creek land is privately owned, and ranchers will sell digging
rights to whoever will pay decent money, paleontologists and commercial
fossil collectors alike.) The collector felt that the site, a
three-foot-deep layer exposed at the surface, was a bust: it was packed
with fish fossils, but they were so delicate that they crumbled into
tiny flakes as soon as they met the air. The fish were encased in layers
of damp, cracked mud and sand that had never solidified; it was so soft
that it could be dug with a shovel or pulled apart by hand. In July,
2012, the collector showed DePalma the site and told him that he was
welcome to it.
“I was immediately very disappointed,” DePalma told
me. He was hoping for a site like the one he’d excavated earlier: an
ancient pond with fine-grained, fossil-bearing layers that spanned many
seasons and years. Instead, everything had been deposited in a single
flood. But as DePalma poked around he saw potential. The flood had
entombed everything immediately, so specimens were exquisitely
preserved. He found many complete fish, which are rare in the Hell Creek
Formation, and he figured that he could remove them intact if he worked
with painstaking care. He agreed to pay the rancher a certain amount
for each season that he worked there. (The specifics of the arrangement,
as is standard practice in paleontology, are a closely guarded secret.
The site is now under exclusive long-term lease.)
The
following July, DePalma returned to do a preliminary excavation of the
site. “Almost right away, I saw it was unusual,” he told me. He began
shovelling off the layers of soil above where he’d found the fish. This
“overburden” is typically material that was deposited long after the
specimen lived; there’s little in it to interest a paleontologist, and
it is usually discarded. But as soon as DePalma started digging he
noticed grayish-white specks in the layers which looked like grains of
sand but which, under a hand lens, proved to be tiny spheres and
elongated droplets. “I think, Holy shit, these look like
microtektites!” DePalma recalled. Microtektites are the blobs of glass
that form when molten rock is blasted into the air by an asteroid impact
and falls back to Earth in a solidifying drizzle. The site appeared to
contain microtektites by the million.
As DePalma carefully
excavated the upper layers, he began uncovering an extraordinary array
of fossils, exceedingly delicate but marvellously well preserved.
“There’s amazing plant material in there, all interlaced and
interlocked,” he recalled. “There are logjams of wood, fish pressed
against cypress-tree root bundles, tree trunks smeared with amber.”
Most fossils end up being squashed flat by the pressure of the overlying
stone, but here everything was three-dimensional, including the fish,
having been encased in sediment all at once, which acted as a support.
“You see skin, you see dorsal fins literally sticking straight up in the
sediments, species new to science,” he said. As he dug, the
momentousness of what he had come across slowly dawned on him. If the
site was what he hoped, he had made the most important paleontological
discovery of the new century.
In
a century and a half of assiduous searching, almost no dinosaur remains
have been found in the layers three metres, or about nine feet, below
the KT boundary, a depth representing many thousands of years.
Photograph by Richard Barnes for The New Yorker
DePalma
grew up in Boca Raton, Florida, and as a child he was fascinated by
bones and the stories they contained. His father, Robert, Sr., practices
endodontic surgery in nearby Delray Beach; his great-uncle Anthony, who
died in 2005, at the age of a hundred, was a renowned orthopedic
surgeon who wrote several standard textbooks on the subject. (Anthony’s
son, Robert’s cousin, is the film director Brian De Palma.)
“Between
the ages of three and four, I made a visual connection with the
gracefulness of individual bones and how they fit together as a system,”
DePalma told me. “That really struck me. I went after whatever on the
dinner table had bones in it.” His family buried their dead pets in one
spot and put the burial markers in another, so that he wouldn’t dig up
the corpses; he found them anyway. He froze dead lizards in ice-cube
trays, which his mother would discover when she had friends over for
iced tea. “I was never into sports,” he said. “They tried to get me to
do that so I would get along with the other kids. But I was digging up
the baseball field looking for bones.”
DePalma’s great-uncle
Anthony, who lived in Pompano Beach, took him under his wing. “I used to
visit him every other weekend and show him my latest finds,” DePalma
said. When he was four, someone at a museum in Texas gave him a fragment
of dinosaur bone, which he took to his great-uncle. “He taught me that
all those little knobs and rough patches and protrusions on a bone had
names, and that the bone also had a name,” DePalma said. “I was
captivated.” At six or seven, on trips to Central Florida with his
family, he started finding his own fossilized bones from mammals dating
back to the Ice Age. He found his first dinosaur bone when he was nine,
in Colorado.
In high school, during the summer and on weekends,
DePalma collected fossils, made dinosaur models, and mounted skeletons
for the Graves Museum of Archaeology and Natural History, in Dania
Beach. He loaned the museum his childhood fossil collection for display,
but in 2004 the museum went bankrupt and many of the specimens were
carted off to a community college. DePalma had no paperwork to prove his
ownership, and a court refused to return his fossils, which numbered in
the hundreds. They were mostly locked away in storage, unavailable for
public display and enjoyment.
Dismayed
by what he called the “wasteful mismanagement” of his collection,
DePalma adopted some unusual collecting practices. Typically,
paleontologists cede the curation and the care of their specimens to the
institutions that hold them. But DePalma insists on contractual clauses
that give him oversight of the management of his specimens. He never
digs on public land, because of what he considers excessive government
red tape. But, without federal support for his work, he must cover
almost all the costs himself. His out-of-pocket expenses for working the
Hell Creek site amount to tens of thousands of dollars. He helps defray
the expenses by mounting fossils, doing reconstructions, and casting
and selling replicas for museums, private collectors, and other clients.
At times, his parents have chipped in. “I squeak by,” he said. “If it’s
a tossup between getting more PaleoBond”—an expensive liquid glue used
to hold fossils together—“or changing the air-conditioning filter, I’m
getting the PaleoBond.” He is single, and shares a three-bedroom
apartment with casts of various dinosaurs, including one of a Nanotyrannus. “It’s hard to have a life outside of my work,” he said.
DePalma’s
control of his research collection is controversial. Fossils are a big
business; wealthy collectors pay hundreds of thousands of dollars, even
millions, for a rare specimen. (In 1997, a T. rex
nicknamed Sue was sold at a Sotheby’s auction, to the Field Museum of
Natural History, in Chicago, for more than $8.3 million.) The American
market is awash in fossils illegally smuggled out of China and Mongolia.
But in the U.S. fossil collecting on private property is legal, as is
the buying, selling, and exporting of fossils. Many scientists view this
trade as a threat to paleontology and argue that important fossils
belong in museums. “I’m not allowed to have a private collection of
anything I’m studying,” one prominent curator told me. DePalma insists
that he maintains “the best of both worlds” for his fossils. He has
deposited portions of his collection at several nonprofit institutions,
including the University of Kansas, the Palm Beach Museum of Natural
History, and Florida Atlantic University; some specimens are temporarily
housed in various analytical labs that are conducting tests on them—all
overseen by him.
In 2013, DePalma briefly made news with a paper he published in the Proceedings of the National Academy of Sciences.
Four years earlier, in Hell Creek, he and a field assistant, Robert
Feeney, found an odd, lumpy growth of fossilized bone that turned out to
be two fused vertebrae from the tail of a hadrosaur, a duck-billed
dinosaur from the Cretaceous period. DePalma thought that the bone might
have grown around a foreign object and encased it. He took it to
Lawrence Memorial Hospital, in Kansas, where a CT technician scanned it
for free in the middle of the night, when the machine was idle. Inside
the nodule was a broken tyrannosaur tooth; the hadrosaur had been bitten
by a tyrannosaur and escaped.
The discovery helped refute an old hypothesis, revived by the formidable paleontologist Jack Horner, that T. rex was solely a scavenger. Horner argued that T. rex
was too slow and lumbering, its arms too puny and its eyesight too
poor, to prey on other creatures. When DePalma’s find was picked up by
the national media, Horner dismissed it as “speculation” and merely “one
data point.” He suggested an alternative scenario: the T. rex
might have accidentally bitten the tail of a sleeping hadrosaur,
thinking that it was dead, and then “backed away” when it realized its
mistake. “I thought that was absolutely preposterous,” DePalma told me.
At the time, he told the Los Angeles Times, “A scavenger doesn’t come across a food source and realize all of a sudden that it’s alive.” Horner eventually conceded that T. rex
may have hunted live prey. But, when I asked Horner about DePalma
recently, he said at first that he didn’t remember him: “In the
community, we don’t get to know students very well.”
Without
his Ph.D., DePalma remains mostly invisible, awaiting the stamp of
approval that signals the beginning of a serious research career.
Several paleontologists I talked to had not heard of him. Another, who
asked not to be named, said, “Finding that kind of fossil was pretty
cool, but not life-changing. People sometimes think I’m dumb because I
often say I don’t have the answers—we weren’t there when a fossil was
formed. There are other people out there who say they do know, and he’s
one of those people. I think he can overinterpret.”
After
receiving DePalma’s e-mail, I made arrangements to visit the Hell Creek
site; three weeks later I was in Bowman. DePalma pulled up to my hotel
in a Toyota 4Runner, its stereo blasting the theme to “Raiders of the
Lost Ark.” He wore a coarse cotton work shirt, cargo pants with canvas
suspenders, and a suède cowboy hat with the left brim snapped up. His
face was tanned from long days in the sun and he had a five-day-old
beard.
I
got in, and we drove for an hour or so, turning through a ranch gate
and following a maze of bone-rattling roads that eventually petered out
in a grassy basin. The scattered badlands of Hell Creek form an
otherworldly landscape. This is far-flung ranching and farming country;
prairies and sunflower fields stretch to the horizon, domed by the great
blue skies of the American West. Roads connect small towns—truck stop,
church, motel, houses and trailers—and lonely expanses roll by in
between. Here and there in the countryside, abandoned farmhouses lean
into the ground. Over millions of years, the Hell Creek layer has been
heavily eroded, leaving only remnants, which jut from the prairie like
so many rotten teeth. These lifeless buttes and pinnacles are striped in
beige, chocolate, yellow, maroon, russet, gray, and white. Fossils,
worked loose by wind and rain, spill down the sides.
When we
arrived, DePalma’s site lay open in front of us: a desolate hump of
gray, cracked earth, about the size of two soccer fields. It looked as
if a piece of the moon had dropped there. One side of the deposit was
cut through by a sandy wash, or dry streambed; the other ended in a low
escarpment. The dig was a three-foot-deep rectangular hole, sixty feet
long by forty feet wide. A couple of two-by-fours, along with various
digging tools and some metal pipe for taking core samples, leaned
against the far side of the hole. As we strolled around the site, I
noticed on DePalma’s belt a long fixed-blade knife and a sheathed
bayonet—a Second World War relic that his uncle gave him when he was
twelve, he said.
He recalled the moment of discovery. The first
fossil he removed, earlier that summer, was a five-foot-long freshwater
paddlefish. Paddlefish still live today; they have a long bony snout,
with which they probe murky water in search of food. When DePalma took
out the fossil, he found underneath it a tooth from a mosasaur, a giant
carnivorous marine reptile. He wondered how a freshwater fish and a
marine reptile could have ended up in the same place, on a riverbank at
least several miles inland from the nearest sea. (At the time, a shallow
body of water, called the Western Interior Seaway, ran from the
proto-Gulf of Mexico up through part of North America.) The next day,
he found a two-foot-wide tail from another marine fish; it looked as if
it had been violently ripped from the fish’s body. “If the fish is dead
for any length of time, those tails
decay and fall apart,” DePalma said. But this one was perfectly intact,
“so I knew that it was transported at the time of death or around then.”
Like the mosasaur tooth, it had somehow ended up miles inland from the
sea of its origin. “When I found that, I thought, There’s no way, this
can’t be right,” DePalma said. The discoveries hinted at an
extraordinary conclusion that he wasn’t quite ready to accept. “I was
ninety-eight per cent convinced at that point,” he said.
The
following day, DePalma noticed a small disturbance preserved in the
sediment. About three inches in diameter, it appeared to be a crater
formed by an object that had fallen from the sky and plunked down in
mud. Similar formations, caused by hailstones hitting a muddy surface,
had been found before in the fossil record. As DePalma shaved back the
layers to make a cross-section of the crater, he found the thing
itself—not a hailstone but a small white sphere—at the bottom of the
crater. It was a tektite, about three millimetres in diameter—the
fallout from an ancient asteroid impact. As he continued excavating, he
found another crater with a tektite at the bottom, and another, and
another. Glass turns to clay over millions of years, and these tektites
were now clay, but some still had glassy cores. The microtektites he had
found earlier might have been carried there by water, but these had
been trapped where they fell—on what, DePalma believed, must have been
the very day of the disaster.
“When I saw that, I knew this wasn’t
just any flood deposit,” DePalma said. “We weren’t just near the KT
boundary—this whole site is the KT boundary!” From
surveying and mapping the layers, DePalma hypothesized that a massive
inland surge of water flooded a river valley and filled the low-lying
area where we now stood, perhaps as a result of the KT-impact tsunami,
which had roared across the proto-Gulf and up the Western Interior
Seaway. As the water slowed and became slack, it deposited everything
that had been caught up in its travels—the heaviest material first, up
to whatever was floating on the surface. All of it was quickly entombed
and preserved in the muck: dying and dead creatures, both marine and
freshwater; plants, seeds, tree trunks, roots, cones, pine needles,
flowers, and pollen; shells, bones, teeth, and eggs; tektites, shocked
minerals, tiny diamonds, iridium-laden dust, ash, charcoal, and
amber-smeared wood. As the sediments settled, blobs of glass rained into
the mud, the largest first, then finer and finer bits, until grains
sifted down like snow.
“We have the whole KT event preserved in
these sediments,” DePalma said. “With this deposit, we can chart what
happened the day the Cretaceous died.” No paleontological site remotely
like it had ever been found, and, if DePalma’s hypothesis proves
correct, the scientific value of the site will be immense. When Walter
Alvarez visited the dig last summer, he was astounded. “It is truly a
magnificent site,” he wrote to me, adding that it’s “surely one of the
best sites ever found for telling just what happened on the day of the
impact.”
When
DePalma finished showing me the dig, he introduced me to a field
assistant, Rudy Pascucci, the director of the Palm Beach Museum.
Pascucci, a muscular man in his fifties, was sunburned and unshaven, and
wore a sleeveless T-shirt, snakeproof camouflage boots, and a dusty
Tilley hat. The two men gathered their tools, got down on the floor of
the hole, and began probing the three-foot-high walls of the deposit.
For
rough digging, DePalma likes to use his bayonet and a handheld Marsh
pick, popularized by the nineteenth-century Yale paleontologist
Othniel C. Marsh, who pioneered dinosaur-hunting in the American West
and discovered eighty new species. The pick was given to him by David
Burnham, his thesis adviser at Kansas, when he completed his master’s
degree. For fine work, DePalma uses X-Acto knives and brushes—the
typical tools of a paleontologist—as well as dental instruments given to
him by his father.
The deposit consisted of dozens of thin layers
of mud and sand. Lower down, it graded into a more turbulent band of
sand and gravel, which contained the heavier fish fossils, bones, and
bigger tektites. Below that layer was a hard surface of sandstone, the
original Cretaceous bedrock of the site, much of which had been scoured
smooth by the flood.
Paleontology is maddening work, its progress
typically measured in millimetres. As I watched, DePalma and Pascucci
lay on their stomachs under the beating sun, their eyes inches from the
dirt wall, and picked away. DePalma poked the tip of an X-Acto into the
thin laminations of sediment and loosened one dime-size flake at a time;
he’d examine it closely, and, if he saw nothing, flick it away. When
the chips accumulated, he gathered them into small piles with a
paintbrush; when those piles accumulated, Pascucci swept them into
larger piles with a broom and then shovelled them into a heap at the far
end of the dig.
Occasionally, DePalma came across small plant
fossils—flower petals, leaves, seeds, pine needles, and bits of bark.
Many of these were mere impressions in the mud, which would crack and
peel as soon as they were exposed to the air. He quickly squirted them
with PaleoBond, which soaked into the fossils and held them
together. Or, using another technique, he mixed a batch of plaster and
poured it on the specimen before it fell apart. This would preserve,
in plaster, a reverse image of the fossil; the original was too
short-lived to be saved.
When the mosquitoes got bad, DePalma took
out a briar pipe and packed it with Royal Cherry Cavendish tobacco. He
put a lighter to it and vigorously puffed, wreathing himself in
sickly-sweet smoke, then went back to work. “I’m like a shopaholic in a
shoe store,” he said. “I want everything!”
He
showed me the impression of a round object about two inches wide. “This
is either a flower or an echinoderm,” he said, referring to a group of
marine life-forms that includes sea urchins and starfish. “I’ll figure
it out in the lab.” He swiftly entombed it in PaleoBond and plaster.
Next, he found a perfect leaf, and near that a seed from a pinecone.
“Cretaceous mulch,” he said, dismissively; he already had many similar
examples. He found three more small craters with tektites in them, which
he sectioned and photographed. Then his X-Acto blade turned up a tiny
brown bone—a jaw, less than a quarter inch in length. He held it up
between his fingers and peered at it with a lens.
“A mammal,” he
said. “This one was already dead when it was buried.” Weeks later, in
the lab, he identified the jaw as probably belonging to a mammal
distantly related to primates—including us.
In one fell swoop, DePalma may have filled in the gap in the fossil record.
Photograph by Richard Barnes for The New Yorker
Half
an hour later, DePalma discovered a large feather. “Every day is
Christmas out here,” he said. He exposed the feather with precise
movements. It was a crisp impression in the layer of mud, perhaps
thirteen inches long. “This is my ninth feather,” he said. “The first
fossil feathers ever found at Hell Creek. I’m convinced these are
dinosaur feathers. I don’t know for sure. But these are primitive
feathers, and most are a foot long. There are zero birds that big from
Hell Creek with feathers this primitive. It’s more parsimonious to
suggest it was a known dinosaur, most likely a theropod, possibly a
raptor.” He kept digging. “Maybe we’ll find the raptor that these
feathers came from, but I doubt it. These feathers could have floated
from a long way off.”
His X-Acto knife unearthed the edge of a
fossilized fin. Another paddlefish came to light; it later proved to be
nearly six feet long. DePalma probed the sediment around it, to gauge
its position and how best to extract it. As more of it was exposed, we
could clearly see that the fish’s two-foot-long snout had broken when it
was forced—probably by the flood’s surge—against the branches of a
submerged araucaria tree. He noted that every fish he’d found in the
site had died with its mouth open, which may indicate that the fish had
been gasping as they suffocated in the sediment-laden water.
“Most
died in a vertical position in the sediment, didn’t even tip over on
their sides,” he said. “And they weren’t scavenged, because whatever
would have dug them up afterward was probably gone.” He chipped away
around the paddlefish, exposing a fin bone, then a half-dollar-size
patch of fossilized skin with the scales perfectly visible. He treated
these by saturating them with his own special blend of hardener. Because
of the extreme fragility of the fossils, he would take them back to his
lab, in Florida, totally encased in sediment, or “matrix.” In the lab,
he would free each fossil under a magnifying glass, in precisely
controlled conditions, away from the damaging effects of sun, wind, and
aridity.
As DePalma worked around the paddlefish, more of the
araucaria branch came to light, including its short, spiky needles.
“This tree was alive when it was buried,” he said. Then he noticed a
golden blob of amber stuck to the branch. Amber is preserved tree resin
and often contains traces of whatever was in the air at the time,
trapping the atmospheric chemistry and even, sometimes, insects and
small reptiles. “This is Cretaceous flypaper,” he said. “I can’t wait to
get this back to the lab.”
An
hour later, he had chiselled all the way around the fish, leaving it
encased in matrix, supported by a four-inch-tall pedestal of rock. “I’m
pretty sure this is a species new to science,” he said. Because the soft
tissue had also fossilized, he said, even the animal’s stomach contents
might still be present.
He straightened up. “Time to plaster,” he
said. He took off his shirt and began mixing a five-gallon bucket of
plaster with his hands, while Pascucci tore strips of burlap. DePalma
took a two-by-four and sawed off two foot-long pieces and placed them
like splints on either side of the sediment-encased fossil. One by one,
he dipped the burlap strips in the plaster and draped them across the
top and the sides of the specimen. He added rope handles and plastered
them in. An hour later, when the plaster had cured, he chiselled through
the rock pedestal beneath the fossil and flipped the specimen over,
leaving the underside exposed. Back in the lab, he would go through this
surface to access the fossil, with the plaster jacket acting as a
cradle below. Using the rope handles, DePalma and Pascucci lugged the
specimen, which weighed perhaps two hundred pounds, to the truck and
loaded it into the back. Later, DePalma
would store it behind a friend’s ranch house, where all his jacketed
fossils from the season were laid out in rows, covered with tarps.
DePalma
resumed digging. Gusts of wind stirred up clouds of dust, and rain
fell; when the weather cleared, the late-afternoon sun spilled across
the prairie. DePalma was lost in another day, in another time. “Here’s a
piece of wood with bark-beetle traces,” he said. Plant fossils from the
first several million years after the impact show almost no signs of
such damage; the insects were mostly gone. The asteroid had likely
struck in the fall, DePalma speculated. He had reached this conclusion
by comparing the juvenile paddlefish and sturgeon he’d found with the
species’ known growth rates and hatching seasons; he’d also found the
seeds of conifers, figs, and certain flowers. “When we analyze the
pollen and diatomaceous particles, that will narrow it down,” he said.
A
core sample from DePalma’s site. The site may hold a precise geological
transcript of the asteroid strike that almost wiped out life on the
planet.
Photograph by Richard Barnes for The New Yorker
“It
solves the question of whether dinosaurs went extinct at exactly that
level or whether they declined before,” the paleontologist Jan Smit
said. “And this is the first time we see direct victims.”
Photograph by Richard Barnes for The New Yorker
In
the week that followed, fresh riches emerged: more feathers, leaves,
seeds, and amber, along with several other fish, three to five feet
long, and a dozen more craters with tektites. I have visited many
paleontological sites, but I had never seen so many specimens found so
quickly. Most digs are boring; days or weeks may pass with little found.
DePalma seemed to make a noteworthy discovery about every half hour.
When
DePalma first visited the site, he noted, partially embedded on the
surface, the hip bone of a dinosaur in the ceratopsian family, of which
triceratops is the best-known member. A commercial collector had tried
to remove it years earlier; it had been abandoned in place and was
crumbling from years of exposure. DePalma initially dismissed it as
“trash” and decried the irresponsibility of the collector. Later,
though, he wondered how the bone, which was heavy, had arrived there,
very close to the high-water mark of the flood. It must have floated, he
said, and to have done so it must have been encased in desiccated
tissue—suggesting that at least one dinosaur species was alive at the
time of the impact. He later found a suitcase-size piece of fossilized
skin from a ceratopsian attached to the hip bone.
At one point,
DePalma set off to photograph the layers of the deposit which had been
cut through and exposed by the sandy wash. He scraped smooth a vertical
section and misted it with water from a spray bottle to bring out the
color. The bottom layer was jumbled; the first rush of water had ripped
up layers of mud, gravel, and rocks and tumbled them about with pieces
of burned (and burning) wood.
Then
DePalma came to a faint jug-shaped outline in the wall of the wash. He
examined it closely. It started as a tunnel at the top of the KT layer,
went down, and then widened into a round cavity, filled with soil of a
different color, which stopped at the hard sandstone of the undisturbed
bedrock layer below. It looked as though a small animal had dug through
the mud to create a hideout. “Is that a burrow?” I asked.
DePalma
scraped the area smooth with his bayonet, then sprayed it. “You’re darn
right it is,” he said. “And this isn’t the burrow of a small dinosaur.
It’s a mammal burrow.” (Burrows have characteristic shapes, depending on
the species that inhabit them.) He peered at it, his eyes inches from
the rock, probing it with the tip of the bayonet. “Gosh, I think it’s
still in there!”
He planned to remove the entire burrow intact, in
a block, and run it through a CT scanner back home, to see what it
contained. “Any Cretaceous mammal burrow is incredibly rare,” he said.
“But this one is impossible—it’s dug right through the KT boundary.”
Perhaps, he said, the mammal survived the impact and the flood, burrowed
into the mud to escape the freezing darkness, then died. “It may have
been born in the Cretaceous and died in the Paleocene,” he said. “And to
think—sixty-six million years later, a stinky monkey is digging it up,
trying to figure out what happened.” He added, “If it’s a new species,
I’ll name it after you.”
When I left Hell Creek, DePalma pressed
me on the need for secrecy: I was to tell no one, not even close
friends, about what he’d found. The history of paleontology is full of
tales of bribery, backstabbing, and double-dealing. In the nineteenth
century, Othniel C. Marsh and Edward Drinker Cope, the nation’s two
leading paleontologists, engaged in a bitter competition to collect
dinosaur fossils in the American West. They raided each other’s
quarries, bribed each other’s crews, and vilified each other in print
and at scientific meetings. In 1890, the New York Herald began a series of sensational articles about the controversy with the headline “Scientists Wage Bitter Warfare.”
The rivalry has since become known as the Bone Wars. The days of
skulduggery in paleontology have not passed; DePalma was deeply
concerned that the site would be expropriated by a major museum.
DePalma
knew that a screwup with this site would probably end his career, and
that his status in the field was so uncertain that he needed to fortify
the find against potential criticism. He had already experienced harsh
judgment when, in 2015, he published a paper
on a new species of dinosaur called a Dakotaraptor, and mistakenly
inserted a fossil turtle bone in the reconstruction. Although rebuilding
a skeleton from thousands of bone fragments that have commingled with
those of other species is not easy, DePalma was mortified by the
attacks. “I never want to go through that again,” he told me.
For
five years, DePalma continued excavations at the site. He quietly shared
his findings with a half-dozen luminaries in the field of KT studies,
including Walter Alvarez, and enlisted their help. During the winter
months, when not in the field, DePalma prepared and analyzed his
specimens, a few at a time, in a colleague’s lab at Florida Atlantic
University, in Boca Raton. The lab was a windowless, wedgelike room in
the geology building, lined with bubbling aquarium tanks and shelves
heaped with books, scientific journals, pieces of coral, mastodon teeth,
seashells, and a stack of .50-calibre machine-gun rounds, dating from
the Second World War, that the lab’s owner had recovered from the bottom
of the Atlantic Ocean. DePalma had carved out a space for himself in a
corner, just large enough for him to work on one or two jacketed fossils
at a time.
When
I first visited the lab, in April, 2014, a block of stone three feet
long by eighteen inches wide lay on a table under bright lights and a
large magnifying lens. The block, DePalma said, contained a sturgeon and
a paddlefish, along with dozens of smaller fossils and a single small,
perfect crater with a tektite in it. The lower parts of the block
consisted of debris, fragments of bone, and loose tektites that had been
dislodged and caught up in the turbulence. The block told the story of
the impact in microcosm. “It was a very bad day,” DePalma said. “Look at
these two fish.” He showed me where the sturgeon’s scutes—the sharp,
bony plates on its back—had been forced into the body of the paddlefish.
One fish was impaled on the other. The mouth of the paddlefish was
agape, and jammed into its gill rakers were microtektites—sucked in by
the fish as it tried to breathe. DePalma said, “This fish was likely
alive for some time after being caught in the wave, long enough to gasp
frenzied mouthfuls of water in a vain attempt to survive.”
Gradually,
DePalma was piecing together a potential picture of the disaster. By
the time the site flooded, the surrounding forest was already on fire,
given the abundance of charcoal, charred wood, and amber he’d found at
the site. The water arrived not as a curling wave but as a powerful,
roiling rise, packed with disoriented fish and plant and animal debris,
which, DePalma hypothesized, were laid down as the water slowed and
receded.
In the lab, DePalma showed me magnified cross-sections of
the sediment. Most of its layers were horizontal, but a few formed
curlicues or flamelike patterns called truncated flame structures, which
were caused by a combination of weight from above and mini-surges in
the incoming water. DePalma found five sets of these patterns. He turned
back to the block on his table and held a magnifying lens up to the
tektite. Parallel, streaming lines were visible on its surface—Schlieren
lines, formed by two types of molten glass swirling together as the
blobs arced through the atmosphere. Peering through the lens, DePalma
picked away at the block with a dental probe. He soon exposed a section
of pink, pearlescent shell, which had been pushed up against the
sturgeon. “Ammonite,” he said. Ammonites were marine mollusks that
somewhat resemble the present-day nautilus, although they were more
closely related to squid and octopi. As DePalma uncovered more of the
shell, I watched its vibrant color fade. “Live ammonite, ripped apart by
the tsunami—they don’t travel well,” he said. “Genus Sphenodiscus,
I would think.” The shell, which hadn’t previously been documented in
the Hell Creek Formation, was another marine victim tossed inland.
He
stood up. “Now I’m going to show you something special,” he said,
opening a wooden crate and removing an object that was covered in
aluminum foil. He unwrapped a sixteen-inch fossil feather, and held it
in his palms like a piece of Lalique glass. “When I found the first
feather, I had about twenty seconds of disbelief,” he said. DePalma had
studied under Larry Martin, a world authority on the Cretaceous
predecessors of birds, and had been “exposed to a lot of fossil
feathers. When I encountered this damn thing, I immediately understood
the importance of it. And now look at this.”
From the lab table,
he grabbed a fossil forearm belonging to Dakotaraptor, the dinosaur
species he’d discovered in Hell Creek. He pointed to a series of regular
bumps on the bone. “These are probably quill knobs,” he said. “This
dinosaur had feathers on its forearms. Now watch.” With precision
calipers, he measured the diameter of the quill knobs, then the diameter
of the quill of the fossil feather; both were 3.5 millimetres. “This
matches,” he said. “This says a feather of this size would be associated
with a limb of this size.”
There was more, including a piece of a
partly burned tree trunk with amber stuck to it. He showed me a photo
of the amber seen through a microscope. Trapped inside were two impact
particles—another landmark discovery, because the amber would have
preserved their chemical composition.
(All other tektites found from the impact, exposed to the elements for
millions of years, have chemically changed.) He’d also found scores of
beautiful examples of lonsdaleite, a hexagonal form of diamond that is
associated with impacts; it forms when carbon in an asteroid is
compressed so violently that it crystallizes into trillions of
microscopic grains, which are blasted into the air and drift down.
Finally,
he showed me a photograph of a fossil jawbone; it belonged to the
mammal he’d found in the burrow. “This is the jaw of Dougie,” he said.
The bone was big for a Cretaceous mammal—three inches long—and almost
complete, with a tooth. After my visit to Hell Creek, DePalma had
removed the animal’s burrow intact, still encased in the block of
sediment, and, with the help of some women who worked as cashiers at the
Travel Center, in Bowman, hoisted it into the back of his truck. He
believes that the jaw belonged to a marsupial that looked like a weasel.
Using the tooth, he could conduct a stable-isotope study to find out
what the animal ate—“what the menu was after the disaster,” he said. The
rest of the mammal remains in the burrow, to be researched later.
DePalma
says that he’s discovered more than a dozen new species of animals and
plants, and identified the broken teeth and bones, including hatchling
remains, of almost every dinosaur group known from Hell Creek.
Photograph by Richard Barnes for The New Yorker
DePalma
listed some of the other discoveries he’s made at the site: several
flooded ant nests, with drowned ants still inside and some chambers
packed with microtektites; a possible wasp burrow; another mammal
burrow, with multiple tunnels and galleries; shark teeth; the thigh
bone of a large sea turtle; at least three new fish species; a gigantic
ginkgo leaf and a plant that was a relative of the banana; more than a
dozen new species of animals and plants; and several other burrow types.
At
the bottom of the deposit, in a mixture of heavy gravel and tektites,
DePalma identified the broken teeth and bones, including hatchling
remains, of almost every dinosaur group known from Hell Creek, as well
as pterosaur remains, which had previously been found only in layers far
below the KT boundary. He found, intact, an unhatched egg containing an
embryo—a fossil of immense research value. The egg and the other
remains suggested that dinosaurs and major reptiles were probably not
staggering into extinction on that fateful day. In one fell swoop,
DePalma may have solved the three-metre problem and filled in the gap in
the fossil record.
By
the end of the 2013 field season, DePalma was convinced that the site
had been created by an impact flood, but he lacked conclusive evidence
that it was the KT impact. It was possible that it resulted from another
giant asteroid strike that occurred at around the same time.
“Extraordinary discoveries require extraordinary evidence,” he said. If
his tektites shared the same geochemistry as tektites from the Chicxulub
asteroid, he’d have a strong case. Deposits of Chicxulub tektites are
rare; the best source, discovered in 1990, is a small outcrop in Haiti,
on a cliff above a road cut. In late January, 2014, DePalma went there
to gather tektites and sent them to an independent lab in Canada, along
with tektites from his own site; the samples were analyzed at the same
time, with the same equipment. The results indicated a near-perfect
geochemical match.
In the first few years after DePalma’s
discoveries, only a handful of scientists knew about them. One was David
Burnham, DePalma’s thesis adviser at Kansas, who estimates that
DePalma’s site will keep specialists busy for at least half a century.
“Robert’s got so much stuff that’s unheard of,” Burnham told me. “Amber
with tektites embedded in it—holy cow! The dinosaur feathers are crazy
good, but the burrow makes your head reel.” In paleontology, the term Lagerstätte
refers to a rare type of fossil site with a large variety of specimens
that are nearly perfectly preserved, a sort of fossilized ecosystem. “It
will be a famous site,” Burnham said. “It will be in the textbooks. It
is the Lagerstätte of the KT extinction.”
Jan
Smit, a paleontologist at Vrije University, in Amsterdam, and a world
authority on the KT impact, has been helping DePalma analyze his
results, and, like Burnham and Walter Alvarez, he is a co-author of a
scientific paper that DePalma is publishing about the site. (There are
eight other co-authors.) “This is really a major discovery,” Smit said.
“It solves the question of whether dinosaurs went extinct at exactly
that level or whether they declined before. And this is the first time
we see direct victims.” I asked if the results would be controversial.
“When I saw his data with the paddlefish, sturgeon, and ammonite, I
think he’s right on the spot,” Smit said. “I am very sure he has a pot
of gold.”
In
September of 2016, DePalma gave a brief talk about the discovery at the
annual meeting of the Geological Society of America, in Colorado. He
mentioned only that he had found a deposit from a KT flood that had
yielded glass droplets, shocked minerals, and fossils. He had christened
the site Tanis, after the ancient city in Egypt, which was featured in
the 1981 film “Raiders of the Lost Ark” as the resting place of the Ark
of the Covenant. In the real Tanis, archeologists found an inscription
in three writing systems, which, like the Rosetta stone, was crucial in
translating ancient Egyptian. DePalma hopes that his Tanis site will help decipher what happened on the first day after the impact.
The
talk, limited though it was, caused a stir. Kirk Cochran, a professor
at the School of Marine and Atmospheric Science at Stony Brook
University, in New York, recalled that when DePalma presented his
findings there were gasps of amazement in the audience. Some scientists
were wary. Kirk Johnson, the director of the Smithsonian’s National
Museum of Natural History, told me that he knew the Hell Creek area
well, having worked there since 1981. “My warning lights were flashing
bright red,” he told me. “I was so skeptical after the talk I was
convinced it was a fabrication.” Johnson, who had been mapping the KT
layer in Hell Creek, said that his research indicated that Tanis was at
least forty-five feet below the KT boundary and perhaps a hundred
thousand years older. “If it’s what it’s said to be,” Johnson said,
“it’s a fabulous discovery.” But he declared himself “uneasy” until he
could see DePalma’s paper.
One prominent West Coast paleontologist
who is an authority on the KT event told me, “I’m suspicious of the
findings. They’ve been presented at meetings in various ways with
various associated extraordinary claims. He could have stumbled on
something amazing, but he has a reputation for making a lot out of a
little.” As an example, he brought up DePalma’s paper on Dakotaraptor,
which he described as “bones he basically collected, all in one area,
some of which were part of a dinosaur, some of which were part of a
turtle, and he put it all together as a skeleton of one animal.” He also
objected to what he felt was excessive secrecy surrounding the Tanis
site, which has made it hard for outside scientists to evaluate
DePalma’s claims.
Johnson, too, finds the lack of transparency,
and the dramatic aspects of DePalma’s personality, unnerving. “There’s
an element of showmanship in his presentation style that does not add to
his credibility,” he said. Other paleontologists told me that they were
leery of going on the record with criticisms of DePalma and his
co-authors. All expressed a desire to see the final paper, which will be
published next week, in the Proceedings of the National Academy of Sciences, so that they could evaluate the data for themselves.
After
the G.S.A. talk, DePalma realized that his theory of what had happened
at Tanis had a fundamental problem. The KT tsunami, even moving at more
than a hundred miles an hour, would have taken many hours to travel the
two thousand miles to the site. The rainfall of glass blobs, however,
would have hit the area and stopped within about an hour after the
impact. And yet the tektites fell into an active flood. The timing was
all wrong.
This was not a paleontological question; it was a
problem of geophysics and sedimentology. Smit was a sedimentologist, and
another researcher whom DePalma shared his data with, Mark Richards,
now of the University of Washington, was a geophysicist. At dinner one
evening in Nagpur, India, where they were attending a conference, Smit
and Richards talked about the problem, looked up a few papers, and later
jotted down some rough calculations. It was immediately apparent to
them that the KT tsunami would have arrived too late to capture the
falling tektites; the wave would also have been too diminished by its
long journey to account for the thirty-five-foot rise of water at
Tanis. One of them proposed that the wave might have been created by a
curious phenomenon known as a seiche. In large earthquakes, the shaking
of the ground sometimes causes water in ponds, swimming pools, and
bathtubs to slosh back and forth. Richards recalled that the 2011
Japanese earthquake produced bizarre, five-foot seiche waves in an
absolutely calm Norwegian fjord thirty minutes after the quake, in a
place unreachable by the tsunami.
Richards
had previously estimated that the worldwide earthquake generated by the
KT impact could have been a thousand times stronger than the biggest
earthquake ever experienced in human history. Using that gauge, he
calculated that potent seismic waves would have arrived at Tanis six
minutes, ten minutes, and thirteen minutes after the impact. (Different
types of seismic waves travel at different speeds.) The brutal shaking
would have been enough to trigger a large seiche, and the first blobs of
glass would have started to rain down seconds or minutes afterward.
They would have continued to fall as the seiche waves rolled in and out,
depositing layer upon layer of sediment and each time sealing the
tektites in place. The Tanis site, in short, did not span the first day
of the impact: it probably recorded the first hour or so. This fact, if
true, renders the site even more fabulous than previously thought. It is
almost beyond credibility that a precise geological transcript of the
most important sixty minutes of Earth’s history could still exist
millions of years later—a sort of high-speed, high-resolution video of
the event recorded in fine layers of stone. DePalma said, “It’s like
finding the Holy Grail clutched in the bony fingers of Jimmy Hoffa,
sitting on top of the Lost Ark.” If Tanis had been closer to or farther
from the impact point, this beautiful coincidence of timing could not
have happened. “There’s nothing in the world that’s ever been seen like
this,” Richards told me.
-=-=-=
One
day sixty-six million years ago, life on Earth almost came to a
shattering end. The world that emerged after the impact was a much
simpler place. When sunlight finally broke through the haze, it
illuminated a hellish landscape. The oceans were empty. The land was
covered with drifting ash. The forests were charred stumps. The cold
gave way to extreme heat as a greenhouse effect kicked in. Life mostly
consisted of mats of algae and growths of fungus: for years after the
impact, the Earth was covered with little other than ferns. Furtive,
ratlike mammals lived in the gloomy understory.
But eventually
life emerged and blossomed again, in new forms. The KT event continues
to attract the interest of scientists in no small part because the ashen
print it left on the planet is an existential reminder. “We wouldn’t be
here talking on the phone if that meteorite hadn’t fallen,” Smit told
me, with a laugh. DePalma agreed. For the first hundred million years of
their existence, before the asteroid struck, mammals scurried about the
feet of the dinosaurs, amounting to little. “But when the dinosaurs
were gone it freed them,” DePalma said. In the next epoch, mammals
underwent an explosion of adaptive radiation, evolving into a dazzling
variety of forms, from tiny bats to gigantic titanotheres, from horses
to whales, from fearsome creodonts to large-brained primates with hands
that could grasp and minds that could see through time.
“We can
trace our origins back to that event,” DePalma said. “To actually be
there at this site, to see it, to be connected to that day, is a special
thing. This is the last day of the Cretaceous. When you go one layer
up—the very next day—that’s the Paleocene, that’s the age of mammals,
that’s our age.” ♦
This article appears in the print edition of the April 8, 2019, issue, with the headline “The Day the Earth Died.” The New Yorker
