Comet or Asteroid Shower in the Late Eocene?

摘要

In the late Eocene [～ 34 to 36.5 million years ago (Ma)], the deep-water carbonates of the Massig-nano section (Italy) were enriched in extraterrestrial ~3He, indicating a higher delivery of interplanetary dust particles (IDPs) to Earth (1). This ～ 2.5-million-year-long increase in the flux of IDPs is attributed to the arrival in the inner solar system of long-period comets, triggered by a perturbation of the Oort cloud (1). The two largest terrestrial craters in the Cenozoic, the 100-km Popigai (dated 35.7 ± 0.2 Ma) in northern Siberia and the 85-km Chesapeake Bay (dated 35.5 ± 0.6 Ma) just offshore Virginia, formed during the same time interval (2); they are likely the result of cometary impacts (1).