-Potential asteroid shower in the late Eocene (35 milllion years ago)

-In 2004, we have proposed that the high level interplanetary dust particles in marine sediments and the presence of several large impact structures in the Late Eocene was caused by a major collision in the asteroid belt some ~ 35 million years ago. This hypothesis conflicts with the accepted view, advocated in 1998 by Kan Farley of Caltech that this period of high-level bombardment on Earth resulted from arrival in the inner solar system of a comet shower, triggered by a perturbation of the Oort cloud. Our hypothesis is based on the identification using platinum group elemental ratios of the meteorite that formed the Popigai crater (100 km in diameter Siberia, 35, 7 my old) as an ordinary chondrite; a composition incompatible with a cometary origin. All existing data indicate that comets have a carbonaceous chondrite-like composition. We propose to test our hypothesis by identifying the type of projectile responsible for the formation of the 4 other terrestrial craters excavated during the same time-period. If their compositions match that of the Popigai crater (i.e. ordinary chondrite), it will be a significant argument to indicate that the flux of large extraterrestrial objects and fine dust came from a collision in the asteroid belt, and not from the margin of the solar system as currently admitted. Roald Tagle will devote part of his 2 year postdoctoral stay at the VUB to measure platinum group element using preconcentration by NiS fire assay followed by inductively coupled plasma mass spectrometry on the impact melt rock collected from the Logoisk, Wanapitai, Mistastin and Chesapeake Bay craters.