Map For over 150 years scientists have tried to solve the mystery of a controversial cuneiform clay tablet that indicates the so-called Köfel’s impact event was observed in ancient times. The circular stone-cast tablet was recovered from the 650 BC underground library of King Ashurbanipal in Nineveh, Iraq in the late 19th century. Long thought to be an Assyrian tablet, computer analysis has matched it with the sky above Mesopotamia in 3300 BC and proves it to be of much more ancient Sumerian origin. The tablet is an “Astrolabe,” the earliest known astronomical instrument. It consists of a segmented, disk-shaped star chart with marked units of angle measure inscribed upon the rim.