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Keck-II facilitates key new insights into ancient meteorite flux published in Nature Astronomy

Philipp R. Heck, Birger Schmitz, William F. Bottke, Surya S. Rout, Noriko T. Kita, Anders Cronholm, Céline Defouilloy, Andrei Dronov and Fredrik Terfelt. "Rare meteorites common in the Ordovician period." Nature Astronomy 1, no. 190 (2017): 0035.

While the origin and composition of contemporary meteorites are relatively easily mapped, the exact nature of meteorite flux in past geological eras is largely veiled in mystery. Today’s flux consists primarily of chondrites, largely as a result of the so-called L-Chondrite Parent Body Break-Up (LCPB), the largest known asteroid breakup of the past three billion years, which took place in the asteroid belt 466 million years ago. Until recently, little was known about meteorite origin and composition before this event, which caused a dramatic spike in meteorite showers in the Ordovician Period (485-444 mya).

Illustration of asteroid belt breakup event causing meteorite showers

Left: Illustration of asteroid belt breakup event causing meteorite showers. Right: relative abundance of chondrites and achondrties before the LCPB, just after the LCPB, and today. Source: Nature Astronomy.

With the aid of advanced imaging techniques, including 3D-microscopy at NUANCE’s KECK-II facility, Heck et al were able to analyze meteoritic remains found in Ordovician limestone beds in Russia, in order to determine the composition of meteorite falls just before the LCPB. They found that the chemical composition of falls prior to 466 million years ago was dramatically different from that of later showers, with achondrites appearing in much greater abundance than in contemporary falls, which are dominated by chondrites.

These findings not only deepen our understanding of Ordovician meteorite patterns, but also provide a key insight into the history of meteorites on an astronomical timescale: as Francesca DeMeo points out in her comments on the publication (“Meteorites: A shift in shooting stars”) Heck et al’s findings suggest that there is no such thing as a fixed ‘baseline’ pattern for meteorite showers that is only temporarily disrupted by major events. Rather, cataclysms such as the LCPB constantly and irreversibly change the way astronomical history unfolds on earth. The course of shooting stars, it seems, is forever changing.