Earth Impact (IMAGE) Southwest Research Institute Caption This image shows an artist’s depiction of a 10-kilometer (six-mile) diameter asteroid striking the Earth. Approximately 70 of these dinosaur killer-sized or larger impacts hit the Earth over a span that lasted between 3.8 and 1.8 billion years ago. They are capable of producing a global millimeter- to centimeter-thick rock layer that contains impact debris: sand-sized droplets, or spherules, of molten rock that rained down from the huge molten plumes made by the mega-impact. Credit Art by Don Davis Usage Restrictions May be used by media and the public for educational and informational purposes only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.