Straining the limits of the imagination, a team of 26 scientists, including several researchers from UCSB, has theorized that a comet exploded over Canada 12,900 years ago with the force of millions of atomic bombs, igniting continental wildfires, destroying the culture of a prehistoric people and wiping out the big mammals that roamed the land, from woolly mammoths to sabertooth cats.

The comet impact, 12,900 years ago. Map by Mary Koenig/SBN

Skeptics of the theory are saying, “Show me the crater.”

“I’m open to be convinced, if the data can be accumulated,” said Stuart Fiedel, a consulting archaeologist in Virginia and the author of  “Prehistory of the Americas,” a widely-used textbook. “We need a lot more proof from a lot more sites to form a consistent picture.

“Right now, they’ve got this convenient ‘out’ because it exploded over the ice and left no crater. Are we talking about something that blew up over the ice, or hit the ice, or went through the ice and hit the ground, or glanced off the ice and shattered? The traces have to fit consistently with one defined kind of impact.”

Allen West, a retired oil and gas geophysicist from Arizona who called scientists together two years ago to study the comet theory, said it’s likely that all of those things happened — and the traces, he said, fit them all.

“We don’t see a big hole in the ground,” West said. “There could have been airbursts in Siberia, for all we know. But the heaviest bombardment was in the Great Lakes and Canada.” 

TELLTALE LAYER

As proof that a comet laid waste to a continent, the proponents of the new theory point to a carbon-rich layer of sediment, 12,900 years old, that they have tested in 22 locations, from Santa Rosa and San Miguel islands to the Carolinas and from southern Arizona to southern Canada.

The samples contained hundreds of thousands of microscopic “spherules” — tiny balls of carbon, and magnetic balls of iron and titanium — markers of an explosion. Also, there were glass-like bits of hardened molten carbon that could only have been created in an “ET” event, the researchers said. Carbon melts at 7,000 degrees Fahrenheit.

James Kennett, a UCSB paleoceanographer, is a leading proponent of the comet theory. Photo by Michelle Yap

Just last month, Chris Mercer, a UCSB materials scientist, identified nanodiamonds in the carbon spherals and glass-like carbon in these and other samples. Nanodiamonds, carbon crystals invisible to the eye, form under extreme heat and pressure and previously had been recovered only from meteorites. Were they in the comet before it exploded, or did they form as it shattered to pieces on entering the atmosphere? No one knows for sure.

As evidence of a continental catastrophe, researchers say, the layer is chock-full of bits of charcoal, a sure sign of wildfire.

UCSB’s Luann Becker, a geochemist, identified large quantities of soot, a byproduct of fire, in the samples, as well as in a “black mat” of fossilized algae that lies just above the layer in many locations.

In Acapulco, the scientific team presented papers suggesting that a continental conflagration likely caused the sudden extinction of 35 species of large mammals in North America, an event that has stumped scientists since the time of Charles Darwin. Most of the big animals that made it through the fires probably died of starvation, scientists say. Only a handful of species, including moose, elk, deer and caribou, survived.

A handful of comet dust contains microscopic nanodiamonds in molten carbon. Photo by Michelle Yap

“It’s of great interest because it’s a dramatic and abrupt cooling,” Kennett said. “It’s going to be uphill, but if our theory is supported, it does show that extraterrestrial impacts can have a major impact on climate.”

For Kennett and others, the comet theory was one of those “Eureka!” moments when a myriad of perplexing patterns suddenly came into focus.

“As soon as I heard about it, the earliest archaeology in California made a lot more sense than it did before,” said Terry Jones, a Cal-Poly State University archaeolgist who sent a display to Acapulco.

Jones said archaeologists have found many of the superb stone spearheads of the Clovis dating back to 13,000 years, but very few signs of Clovis encampments after that time. The comet, Jones said, supplies the likely reason.

“The Clovis were effectively destroyed,” he said.


THREE MYSTERIES SOLVED?

Proponents of the comet theory say their theory solves three big mysteries of science in one fell swoop:

What triggered the “little ice age”, 12,900 years ago?

Replica of a woolly mammoth, formerly on display at the Santa Barbara Museum of History. Courtesy photo.

And why did the Clovis, skilled hunters of the woolly mammoth, armed with superb stone spears, fade from the archaeological record in North America so abruptly, 12,900 years ago?

Archaeologists such as Douglas Kennett of the University of Oregon, Jim Kennett’s son, who led the presentations on the Clovis people in Acapulco, says he intially dismissed the comet theory but was convinced after the carbon-rich layer was documented in sites across North America.

“I feel we have enough evidence from enough places to put it out there as an idea that has to be tested,” Douglas Kennett said. “We’re still waiting to hear information about how far the effects were distributed. It wasn’t completely devastating from coast-to-coast. The bison made it through, and you could imagine people were in caves.”

The humans would have seen the comet coming, perhaps for weeks, unless it was old and black and invisible, West said.

“These things are far more common than people think,” he said. “Yet we’re not even looking for comets. Much of the research in the past has been looking for asteroids, or ‘planet killers.’

“Here, in effect, was a ‘continent killer.’ ”


DOOM FROM OUTER SPACE

Microscopic magnetic balls of titanium and iron, magnified many times here. Photo by Allen West

In 2001, Topping published a paper with Richard Firestone, a nuclear analytical chemist at the Lawrence Berkeley National Laboratory, suggesting that a distant supernova, or exploding star, had dislodged a group of comet-like objects from their orbits and bombarded the planet with cosmic rays.

West saw the paper a few years later and decided to sample a Clovis site in Murray Springs, Ariz., to see if he could find the tiny magnetic balls. He found them there and at other sites, and he soon called Firestone for help.

One thing led to another, West said. By the end of two years, he had spent $70,000 of his own money on laboratory tests and drafted two dozen geophysicists, geologists, geochemists, archaeologists, climatologists and glaciologists to lend a hand.

Today, along with West, Firestone is a leading theoretician of the comet theory. In examining the samples, the two men found high levels of iridium, a rare metal on Earth that is normally associated with meteorites.

If a comet slammed into Canada, it may explain why there are craters deeper than Death Valley in the Great Lakes, Firestone said.

As catastrophic as the event was, he said, the comet had only 10 percent as much power as the giant asteroid that hit in the earth 65 million years ago, destroying the dinosaurs forever.

But a number of scientists, experts in the trajectory of the Clovis people and prehistoric mammals of North America, do not believe a comet virtually finished off animal life on the planet during the last Ice Age.

“If you track the genesis of the idea, the supernova effect, it’s kind of murky and unsettling,” Fiedel said. “Besides, the earth has been hit by things in the past, and the effects do not seem to be global.”

Up to now, the debate over what happened 12,900 years ago, has been characterized as “ill, chill and kill” — a plague, a rapid climate shift or human hunting, or some combination of the three.

Proponents of the “overkill” theory argue that the mammoths vanished wherever the Clovis arrived in North America. Their line of reasoning has been used to explain the extinction of the pygmy mammoths, cow-sized elephants with huge tusks that inhabited Santa Rosa Island. The bones are believed to be 13,000 years old, overlapping the most recent date for the pygmy mammoths, at 12,900 years.

As Fiedel tells the story, the Clovis didn’t get here until 13,000 years ago, and when they arrived, they began setting fires across North America, perhaps driving game or clearing the vegetation.

“Clovis doesn’t just stop,” Fiedel said. “Clovis is succeeded by other cultures that are derived from it with slight changes in style. The people are clearly continuing. They stop hunting mammoths, which are extinct because people hunted them.”

Paul Martin, a professor emeritus of geosciences at the University of Arizona, and the author of the recent book, “Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America,” is a skeptic, too.

Luann Becker, a UCSB geochemist, identified soot in the prehistoric layer. Courtesy photo

Other scientists, including Becker, started out as doubters and wound up as believers. Becker describes how she felt after her first phone call from West: “I’m going, ‘Who is this person?’ ”

Then Becker tested the prehistoric layer and found an exotic kind of carbon with a shape like a soccer ball. Trapped inside it was helium, another sign of a comet or meteorite.

“We’re all quite surprised at how things have fallen together on this project,” Becker said. “Science like this has never been done."