British scientists have deciphered a mysterious ancient clay tablet and believe they have solved a riddle over a giant asteroid impact more than 5,000 years ago. Geologists have long puzzled over the shape of the land close to the town of Köfels in the Austrian Alps, but were unable to prove it had been caused by an asteroid. Now researchers say their translation of symbols on a star map from an ancient civilisation includes notes on a mile-wide asteroid that later hit Earth - which could have caused tens of thousands of deaths. The circular clay tablet was discovered 150...