The subject of this analysis was an excavated core sample inside the Chicxulub crater off the Yucatan Peninsula, Mexico, which is said to have been formed at the Cretaceous / Paleogene boundary (about 6,600 million years ago).The Chicxulub Crater is the site of an asteroid collision that caused the mass extinction of organisms, including dinosaurs at the end of the Cretaceous, and was the subject of research on the 364th research voyage by the International Deep Sea Science Drilling Program.A detailed geochemical analysis of the impact-derived deposits contained in the excavated sample was performed to clarify how the asteroid-derived material that caused the collision is distributed inside the crater.

　As a result, we found a layer containing a high concentration of "iridium," an element peculiar to asteroid components, at the top of the impact-derived sediments.The concentration was about 30 times higher than the top and bottom.In addition, since iridium was concentrated at the top of the clay layer deposited from seawater, ejecta (collision dust) containing asteroid material scattered and floated in the atmosphere after the collision for several years to several decades. It suggests that it may have accumulated during the period.

　Iridium is an element that is abundant in asteroid materials but rarely contained in earth's surface materials. It is possible to align the time axis of the deposits contained in.This will be an important clue to understand the process of diffusion of substances scattered by asteroid collisions to the whole globe, and may lead to the elucidation of environmental changes before and after the extinction of dinosaurs.

Paper information:[Science Advances] Globally distributed iridium layer preserved within the Chicxulub impact structure