Presence of an iron-rich nanophase material in the upper layer of the Cretaceous-Tertiary boundary clay

We report new geochemical evidence from ten Cretaceous-Tertiary (K-T) bound ary sites in North America and Europe, indicating the presence of a materia l remnant of a large asteroid or comet that struck the Earth at 65.0 Ma. Mo ssbauer spectroscopic data reveals that a ubiquitous iron-rich nanophase ma terial exists at the uppermost part of the K-T boundary layer in the Wester n Hemisphere and in Europe in marine and continental fine-grained sedimenta ry rock. The high surface-to-volume ratio of nanophase material suggests th at it may be the carrier of the iridium abundance enhancement that marks th e K-T boundary. Even more provocative is the possibility that the discovere d nanophase material is, for the most part, composed of the vaporized impac tor after the impact-generated high-temperature vapor plume rose and cooled above the atmosphere.