Ordovician meteor event

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The Ordovician meteor event was a dramatic increase in the rate at which L chondrite meteorites fell to Earth during the Middle Ordovician period, about 467.5±0.28 million years ago,{{cite journal|last1=Korochantseva|first1=Ekaterina |last2=Trieloff|first2=Mario |last3=Lorenz|first3=Cyrill |last4=Buykin|first4=Alexey |last5=Ivanova|first5=Marina |last6=Schwarz|first6=Winfried |last7=Hopp|first7=Jens |last8=Jessberger|first8=Elmar |title=L-chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40 Ar- 39 Ar dating|journal=Meteoritics & Planetary Science |date=2007|volume=42|issue=1|pages=113–130 |doi=10.1111/j.1945-5100.2007.tb00221.x |bibcode=2007M&PS...42..113K|doi-access=free}}{{Cite journal|last1=Lindskog|first1=A. |last2=Costa|first2=M. M. |last3=Rasmussen|first3=C.M.Ø. |last4=Connelly|first4=J. N. |last5=Eriksson|first5=M. E. |date=2017-01-24|title=Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification|journal=Nature Communications|language=En|volume=8|pages=14066 |doi=10.1038/ncomms14066| pmid=28117834|pmc=5286199 |bibcode=2017NatCo...814066L |issn=2041-1723 |quote=It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated}} lasting for about 40 million years. This rate increase is indicated by abundant fossil L chondrite meteorites in a quarry in Sweden and enhanced concentrations of ordinary chondritic chromite grains in sedimentary rocks from this time.H. Haack et al. Meteorite, asteroidal, and theoretical constraints on the 500-Ma disruption of the L chondrite parent body, Icarus, Vol. 119, p. 182 (1996).{{cite journal|last=Heck|first=Philipp |author2=Birger Schmitz |author3=Heinrich Baur |author4=Alex N. Halliday |author-link4 = Alexander Halliday|author5=Rainer Wieler |title=Fast delivery of meteorites to Earth after a major asteroid collision|journal=Nature|date=15 July 2004|volume=430|pages=323–325|bibcode = 2004Natur.430..323H |doi = 10.1038/nature02736|pmid=15254530|issue=6997|s2cid=4393398 }}{{Cite journal|last1=LINDSKOG|first1=Anders |last2=SCHMITZ|first2=Birger |last3=CRONHOLM|first3=Anders |last4=DRONOV|first4=Andrei |date=2012-07-30 |title=A Russian record of a Middle Ordovician meteorite shower: Extraterrestrial chromite at Lynna River, St. Petersburg region|journal=Meteoritics & Planetary Science|language=en |volume=47|issue=8|pages=1274–1290 |doi=10.1111/j.1945-5100.2012.01383.x|bibcode=2012M&PS...47.1274L |issn=1086-9379}}{{Cite journal|date=2010-07-01| title=Extraterrestrial chromite distribution across the mid-Ordovician Puxi River section, central China: Evidence for a global major spike in flux of L-chondritic matter |journal=Icarus|language=en |volume=208|issue=1|pages=36–48 |doi=10.1016/j.icarus.2010.02.004|issn=0019-1035 |last1=Cronholm|first1=Anders |last2=Schmitz|first2=Birger| bibcode=2010Icar..208...36C }}

According to a 2019 study, this temporary increase in the impact rate could have been caused by the destruction of the L chondrite parent body that was {{convert|150|km|0|sp=us}} in diameter and orbited in the asteroid belt between Mars and Jupiter.{{Cite web |last=Nature |first=Research Communities by Springer |date=2019-10-22 |title=Gigantic asteroid collision in the Ordovician period boosted biodiversity on Earth |url=https://communities.springernature.com/posts/gigantic-asteroid-collision-in-the-ordovician-period-boosted-biodiversity-on-earth |access-date=2024-05-16 |website=Research Communities by Springer Nature |language=en}} This occurred around 468 ± 0.3 million years ago having scattered fragments into Earth-crossing orbits, a chronology which is also supported by shock ages in numerous L chondrite meteorites that fall to Earth today.

It has been speculated that this influx contributed to, or possibly even instigated, the Great Ordovician Biodiversification Event, although this has been questioned.{{cite journal|last1=Schmitz|first1=Birger |last2=Harper|first2=David |display-authors=etal|title=Asteroid breakup linked to the Great Ordovician Biodiversification Event|journal=Nature Geoscience|volume=1|date=16 December 2007|pages=49–53 |doi=10.1038/ngeo.2007.37|hdl=1912/2272|url=http://darchive.mblwhoilibrary.org/bitstream/1912/2272/1/Naturegeosciences.pdf|hdl-access=free|archive-url=https://web.archive.org/web/20170922030356/http://darchive.mblwhoilibrary.org/bitstream/handle/1912/2272/Naturegeosciences.pdf?sequence=1|archive-date=22 September 2017|url-status=dead}}[http://dx.doi.org/10.1126/sciadv.aax4184 An extraterrestrial trigger for the mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body], Birger Schmitz et al, AAAS Science Advances, 18 Sep 2019: Vol. 5, no. 9, eaax4184; DOI: 10.1126/sciadv.aax4184, accessed 2019-10-09

A 2024 study found that all of 21 studied craters from this event were at the time within 30° of the equator. Impactors directly from the asteroid belt would be expected to produce a random distribution of craters, so this suggests that the event may have been caused by an asteroid that passed within Earth's Roche limit and broke up into a ring system, material from which then deorbited and formed the craters. It is also speculated that the shading of Earth by this ring may have contributed to the Hirnantian glaciation.{{cite journal |last1=Tomkins |first1=Andrew G. |last2=Martin |first2=Erin L. |last3=Cawood |first3=Peter A. |date=November 2024 |title=Evidence suggesting that earth had a ring in the Ordovician |journal=Earth and Planetary Science Letters |volume=646 |issue= |pages=118991 |doi=10.1016/j.epsl.2024.118991 |doi-access=free}}