This is the story of a star map, one which depicted an ancient asteroid having impacted Earth.

We pick up the story from 150 years ago, when an ancient Sumerian star map was found by Sir Austen Henry Layard, a Victorian archaeologist, in a subterranean library in the by then destroyed Royal Palace at Nineveh (modern day Iraq). This was the ancient Royal Library of Ashurbanipal, named after the last great king of the Neo-ᴀssyrian Empire. He ruled from 669 BC to his death in 631 BC.

The library housed a collection of more than 30,000 clay tablets and fragments containing a panoply of texts in a variety of languages from the 7th century BC. This library is where the famous Epic of Gilgamesh was found, inscribed on a clay tablet in cuneiform script (one of the oldest forms of writing known. It means “wedge-shaped,” because people wrote it using a reed stylus cut to make a wedge-shaped mark on a clay tablet).The library also housed a circular clay tablet, which was made by an ᴀssyrian scribe around 700 BC.

Analysis conducted 150 years later revealed that it reflected the sky above Mesopotamia over 5000 years ago. The tablet is an astrolabe (an earliest known astronomical instrument), with segments depicting a disk-shaped star chart with measurements inscribed on its rim. Known as the Planisphere, it is now held at the British Museum (No K8538) and is approximately 5 inches or 12.7 cm in diameter, with a thickness of 1.2 inches or 3.20 cm.

Finding anything from an ancient library is fantastic enough, but the Planisphere had another surprise. It provided proof of the sophistication of Sumerian astronomy and tells the story of an ancient Sumerian astronomer, who observed a mᴀssive asteroid approaching Earth on June 29, 3123 BC. As this ancient astronomer looked up at this fiery object falling through Earth’s atmosphere, he referred to it as “a white stone bowl approaching from the sky,”. He also precisely measured the cosmic object’s trajectory relative to the stars (with an error of less than one degree according to experts). Quite a few parts of the tablet are missing (approximately 40%), probably destroyed during the sacking of Nineveh and the reverse of the tablet is not inscribed.

For 150 years this tablet puzzled scientists because they could not figure out to what event it referred. Then in 2008, two researchers from Bristol University used modern computer programmes to simulate the trajectories and reconstruct the night sky from all those thousands of years ago. They concluded that the cuneifrom text on the tablet records an ancient asteroid strike, which probably landed somewhere in Europe over 5,600 years ago. This event is now known as the Köfel’s impact event. The asteroid was approximately one kilometer long and the researchers said that it crashed into the Alps at Köfels, Austria.

There is a giant ancient lanslide at Köfels in Austria, which is 500 m thick and five kilometers in diameter. Geologists have long wondered at its origins, ever since it was first observed in the 19th century. It was initially thought that it must have been caused by a large meteor impact but this view went out of favour because there was no crater at Köfels, which meant there could have been no impact.

We know that the tablet reveals the observations of a Sumerian astronomer as he records the events in the sky before dawn on 29 June 3123 BC. On one half of the tablet are planet positions and it even describes the extent of cloud cover. The other half records a large object in the nightsky.

Computer simulations by the Bristol University scientists showed that the trajectory of this object relative to the stars depicted in the tablet reflected the impact at Köfels. The observation indicates that the asteroid is more than a kilometer in diameter and that its original orbit around the Sun was of the Aten type, a classification of asteroids that orbit close to Earth and are resonant with Earth’s orbit.

Such a trajectory could explain the lack of a crater at Köfels. The asteroid’s low incoming angle of only six degrees could indicate that the asteroid clipped a mountain called Gamskogel above the town of Längenfeld, 11 kilometers from Köfels. This would have caused it to explode before final impact. It then became a fireball of approximately five km in diameter that travelled down the valley.

According to the Bristol University researchers “When it hit Köfels it created enormous pressures that pulverised the rock and caused the landslide but because it was no longer a solid object it did not create a classic impact crater.”

Mark Hempsell (one of the researchers), discussing the Köfels event, said: “Another conclusion can be made from the trajectory. The back plume from the explosion (the mushroom cloud) would be bent over the Mediterranean Sea re-entering the atmosphere over the Levant, Sinai, and Northern Egypt.

“The ground heating though very short would be enough to ignite any flammable material – including human hair and clothes.  It is probable more people died under the plume than in the Alps due to the impact blast.“

What a turn of events! An ᴀssyrian scribe in the Royal Palace of Nineveh copied out an ancient document on a clay tablet that described an asteroid impact from 3100 BC. Henry Layard, the archaeologist, found it in the remains of the royal library. The inscriptions of the clay tablet remained a mystery for a 150 years since its discovery, until 2008 when it was finally deciphered to be a Sumerian observation of a one kilometer long asteroid that impacted Köfels in Austria on the morning of June 29, 3123 BC.

The Sumerians are known to have been excellent astronomers and this just goes on to show that the ancients had far superior knowledge than we give them credit for.

There is still doubt by some scientists about the accuracy of the Bristol University researchers’ measurements. Even so, how great it is that there is ancient documentation of an object hurtling towards Earth all those years ago!