An impactful event Glassy silica spherules have been found in marine sediments from three sites across a wide area off the Atlantic coast of the United States, near the stratigraphic level of the Paleocene-Eocene boundary. The characteristics of these specimens are consistent with those of microtektites associated with extraterrestrial impact events. This discovery by Schaller et al. is evidence of an impact event at the time of the Paleocene-Eocene Thermal Maximum, a period during which global temperatures increased rapidly and the carbon cycle was substantially perturbed. Science , this issue p. 225