Ancient Mesopotamia

"...and the seven judges of hell... raised their torches, lighting the land with their livid flame. A stupor of despair went up to heaven when the god of the storm turned daylight into darkness, when he smashed the land like a cup."

So says an account of the Deluge from the Epic of Gilgamesh, circa 2200 BC.

Similar but considerably less powerful versions of the events which some scientists say brought down the world's first civilisations happen frequently, when meteors hit the planet.

Biblical stories, apocalyptic visions, ancient art and scientific data all seem to intersect at around 2350 BC, when one or more catastrophic events wiped out several advanced societies in Europe, Asia and Africa.

Increasingly, some scientists suspect comets and their associated meteor storms were the cause. History and culture provide clues: icons and myths surrounding the alleged cataclysms persist in cults and religions today and even fuel terrorism.

And a newly found two mile-wide crater in Iraq, spotted serendipitously in a perusal of satellite images, could provide a smoking gun. The crater's discovery, which was announced in a recent issue of the journal, Meteoritics & Planetary Science, is a preliminary finding. Scientists stress that a ground expedition is needed to determine if the landform was actually carved out by an impact.

Yet the crater has already added another chapter to an intriguing overall story that is, at best, loosely bound. Many of the pages are washed away or buried. But several plot lines converge in conspicuous ways.

Too many coincidences

Archaeological findings show that in the space of a few centuries, many of the first sophisticated civilisations disappeared.

The Old Kingdom in Egypt fell into ruin. The Akkadian culture of Mesopotamia, possibly the world's first empire, collapsed. Settlements in the ancient Levant, gone. Mesopotamia, Earth's original breadbasket, dust [1].

At around the same time, a period called the Early Bronze Age, apocalyptic writings appeared, fuelling religious beliefs that persist today.

The Epic of Gilgamesh describes the fire, brimstone and flood of possibly mythical events. Omens predicting the Akkadian collapse preserve a record that "many stars were falling from the sky." The "Curse of Akkad," dated to about 2200 BC, speaks of "flaming potsherds raining from the sky."

Roughly 2000 years later, the Jewish astronomer Rabbi bar Nachmani created what could be considered the first impact theory: that Noah's Flood was triggered by two "stars" that fell from the sky. "When God decided to bring about the Flood, He took two stars from Khima, threw them on Earth, and brought about the Flood."

Another thread was woven into the tale when, in 1650, the Irish Archbishop James Ussher mapped out the chronology of the Bible, a feat that included stringing together all the "begats" to count generations, and put Noah's great flood at 2349 BC [2].

All coincidence? A number of scientists don't think so.

Mounting hard evidence collected from tree rings, soil layers and even dust that long ago settled to the ocean floor indicates there were widespread environmental nightmares in the Near East during the Early Bronze Age: abrupt cooling of the climate, sudden floods and surges from the seas, huge earthquakes.

Comet as a culprit

In recent years, the fall of ancient civilisations has come to be viewed not as a failure of social engineering or political might but rather the product of climate change and, possibly, heavenly happenstance. As this new thinking dawned, volcanoes and earthquakes were blamed at first. More recently, a 300-year drought has been the likely suspect.

But now more than ever, it appears a comet could be the culprit. One or more devastating impacts could have rocked the planet, chilled the air, and created unthinkable tidal waves, ocean waves hundreds of feet high. Showers of debris wafting through space, concentrated versions of the dust trails that create the more recent Leonid meteor shower, would have blocked out the sun and delivered horrific rains of fire to Earth for years.

So far, the comet theory lacks firm evidence, such as the discovery of a crater.

Now, though, there is this depression in modern Iraq. It was found accidentally by Sharad Master, a geologist at the University of Witwatersrand in South Africa, while studying satellite images. Master says the crater bears the signature shape and look of an impact caused by a space rock.

The finding has not been developed into a fully-fledged scientific paper, however, nor has it undergone peer review. Scientists in several fields were excited by the possibility, but they expressed caution about interpreting the preliminary analysis and said a full scientific expedition to the site needs to be mounted to determine if the landforms do in fact represent an impact crater.

Researchers would look for shards of melted sand and telltale quartz that had been shocked into existence. If it were a comet, the impact would have occurred on what was once a shallow sea, triggering massive flooding following the fire generated by the object's partial vaporisation as it screamed through the atmosphere. The comet would have plunged through the water and dug into the earth below.

If it proves to be an impact crater, there is a good chance it was dug from the planet less than 6,000 years ago, Master said, because shifting sediment in the region would have buried anything older.

Arriving at an exact date will be difficult, researchers said. "It's an exciting crater if it really is of impact origin," said Bill Napier, an astronomer at the Armagh Observatory.

Cultural impact

Napier said an impact that could carve a hole this large would have packed the energy of several dozen nuclear bombs. The local effect: utter devastation.

"But the cultural effect would be far greater," Napier said in an e-mail interview. "The event would surely be incorporated into the world view of people in the Near East at that time and be handed down through the generations in the form of celestial myths."

Napier and others have also suggested that the swastika, a symbol with roots in Asia stretching back to at least 1400 BC, could be an artist's rendering of a comet, with jets spewing material outward as the head of the comet points earthwards.

But could a single impact of this size take down civilizations on three continents? No way, most experts say.

Napier thinks multiple impacts, and possibly a rain of other smaller meteors and dust, would have been required. He and his colleagues have been arguing since 1982 that such events are possible. And, he says, it might have happened right around the time the first urban civilisations were crumbling.

Napier thinks a comet called Encke, discovered in 1786, is the remnant of a larger comet that broke apart 5,000 years ago. Large chunks and vast clouds of smaller debris were cast into space. Napier said it's possible that Earth ran through that material during the Early Bronze Age.

The night sky would have been lit up for years by a fireworks-like display of comet fragments and dust vaporising upon impact with Earth's atmosphere. The sun would have struggled to shine through the debris. Napier has tied the possible event to a cooling of the climate, measured in tree rings, that ran from 2354-2345 BC.

Supporting evidence

Though no other craters have been found in the region and precisely dated to this time, there is other evidence to suggest the scenario is plausible. Two large impact craters in Argentina are believed to have been created sometime in the past 5,000 years.

Benny Peiser, a social anthropologist at Liverpool John Moores University in England, said roughly a dozen craters are known to have been carved out during the past 10,000 years. Dating them precisely is nearly impossible with current technology. And, Peiser said, whether any of the impact craters thought to have been made in the past 10,000 years can be tied back to a single comet is still unknown.

But he did not discount Napier's scenario.

"There is no scientific reason to doubt that the break-up of a giant comet might result in a shower of cosmic debris," Peiser said. He also points out that because Earth is covered mostly by deep seas, each visible crater represents more ominous statistical possibilities. "For every crater discovered on land, we should expect two oceanic impacts with even worse consequences," he said.

Tidal waves generated in deep water can rise even higher when they reach a shore.

Reverberating today

Peiser studies known craters for clues to the past. But he also examines religions and cults, old and new, for signs of what might have happened way back then.

"I would not be surprised if the notorious rituals of human sacrifice were a direct consequence of attempts to overcome this trauma," he says of the South American impact craters. "Interestingly, the same deadly cults were also established in the Near East during the Bronze Age."

The impact of comets on myth and religion has reverberated through the ages, in Peiser's view.

"One has to take into consideration apocalyptic religions [of today] to understand the far-reaching consequences of historical impacts," he says. "After all, the apocalyptic fear of the end of the world is still very prevalent today and can often lead to fanaticism and extremism."

An obsession with the end of the world provides the legs on which modern-day terrorism stands, Peiser argues. Leaders of fundamentalist terror groups drum into the minds of their followers looming cataclysms inspired by ancient writings. Phrases run along these lines: a rolling up of the sun, darkening of the stars, movement of the mountains, splitting of the sky...

It is in the context of such apocalyptic religions that a large meteorite, enshrined in the Kaba in Mecca, became the most feared and venerated object of the Islamic faith, Peiser said.

By using such language, radical fundamentalist leaders instil "absolute commitment and fanaticism into their followers," Peiser said. "Once you believe that the end is imminent and that your direct action will hasten the coming of end times, every atrocity is sanctioned."

No smoking gun yet

Despite the excitement of the newfound hole in the ground in Iraq, it is still far from clear why so many civilisations collapsed in such a relatively short historical time frame. Few scientists, even those who find evidence to support the idea, are ready to categorically blame a comet.

French soil scientist Marie-Agnes Courty, who in 1997 found material that could only have come from a meteorite and dated it to the Early Bronze Age, urged caution on drawing any conclusions until a smoking gun has been positively identified.

"Certain scientists and the popular press do prefer the idea of linking natural catastrophes and societal collapse," Courty said.

Multiple cosmic impacts are an attractive culprit though, because of the many effects they can have, including some found in real climate and geologic data. The initial impact, if it is on land, vaporises life for miles around. Earthquakes devastate an even wider area. A cloud of debris can block out the sun and alter the climate. The extent and duration of the climate effects is not known for sure, because scientists have never witnessed such an event.

It might not have taken much. Ancient civilisations, which depended on farming and reliable rainfall, were precarious.

Mike Baillie, a professor of palaeoecology at Queens University in Belfast, figures it would have taken just a few bad years to destroy such a society.

Even a single comet impact large enough to have created the Iraqi crater, "would have caused a mini-nuclear winter with failed harvests and famine, bringing down any agriculture-based populations which can survive only as long as their stored food reserves," Baillie said. "So any environmental downturn lasting longer than about three years tends to bring down civilisations."

Other scientists doubt that a single impact would have altered the climate for so long.

Lessons for tomorrow

Either way, there is a giant scar on the planet, near the cradle of civilisation, that could soon begin to provide some solid answers, assuming geologists can get permission to enter Iraq and conduct a study.

"If the crater dated from the third millennium BC, it would be almost impossible not to connect it directly with the demise of the Early Bronze Age civilisations in the Near East," said Peiser.

Perhaps before long all the cometary traditions, myths and scientific fact will be seen to converge at the Iraqi hole in the ground for good reason. Understanding what happened, and how frequent and deadly such impacts might be, is an important tool for researchers like Peiser who aim to estimate future risk and help modern society avoid the fate of the ancients.

"Paradoxically, the Hebrew Bible and other Near Eastern documents have kept alive the memory of ancient catastrophes whose scientific analysis and understanding might now be vital for the protection of our own civilisations from future impacts," Peiser said.

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