Ordovician meteor event explained

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.^{[1] [2]} This 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.^{[1] [3] [4] [5] [6]}

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 150km (90miles) in diameter and orbited in the asteroid belt between Mars and Jupiter.^[7] 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.^{[8] [9]}

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.^[10]

See also

• Österplana 065
• Late Ordovician impact craters
  • Lockne crater
  • Målingen crater
  • Pilot crater
  • Tvären

Notes and References

1. Korochantseva. Ekaterina . Trieloff. Mario . Lorenz. Cyrill . Buykin. Alexey . Ivanova. Marina . Schwarz. Winfried . Hopp. Jens . Jessberger. Elmar . L-chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40 Ar- 39 Ar dating. Meteoritics & Planetary Science . 2007. 42. 1. 113–130 . 10.1111/j.1945-5100.2007.tb00221.x . 2007M&PS...42..113K. free.
2. Lindskog. A. . Costa. M. M. . Rasmussen. C.M.Ø. . Connelly. J. N. . Eriksson. M. E. . 2017-01-24. Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification. Nature Communications. En. 8. 14066 . 10.1038/ncomms14066. 28117834. 5286199 . 2017NatCo...814066L . 2041-1723 . 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.
3. 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).
4. Heck. Philipp . Birger Schmitz . Heinrich Baur . Alex N. Halliday . Alexander Halliday. Rainer Wieler . Fast delivery of meteorites to Earth after a major asteroid collision. Nature. 15 July 2004. 430. 323–325. 2004Natur.430..323H . 10.1038/nature02736. 15254530. 6997. 4393398 .
5. LINDSKOG. Anders . SCHMITZ. Birger . CRONHOLM. Anders . DRONOV. Andrei . 2012-07-30 . A Russian record of a Middle Ordovician meteorite shower: Extraterrestrial chromite at Lynna River, St. Petersburg region. Meteoritics & Planetary Science. en . 47. 8. 1274–1290 . 10.1111/j.1945-5100.2012.01383.x. 2012M&PS...47.1274L . 1086-9379.
6. 2010-07-01. Extraterrestrial chromite distribution across the mid-Ordovician Puxi River section, central China: Evidence for a global major spike in flux of L-chondritic matter . Icarus. en . 208. 1. 36–48 . 10.1016/j.icarus.2010.02.004. 0019-1035 . Cronholm. Anders . Schmitz. Birger. 2010Icar..208...36C .
7. Web site: Nature . Research Communities by Springer . 2019-10-22 . Gigantic asteroid collision in the Ordovician period boosted biodiversity on Earth . 2024-05-16 . Research Communities by Springer Nature . en.
8. Schmitz. Birger . Harper. David . etal. Asteroid breakup linked to the Great Ordovician Biodiversification Event. Nature Geoscience. 1. 16 December 2007. 49–53 . 10.1038/ngeo.2007.37. 23 September 2016 -->. 1912/2272. free. https://web.archive.org/web/20170922030356/http://darchive.mblwhoilibrary.org/bitstream/handle/1912/2272/Naturegeosciences.pdf?sequence=1. 22 September 2017. dead.
9. 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
10. Tomkins . Andrew G. . Martin . Erin L. . Cawood . Peter A. . November 2024 . Evidence suggesting that earth had a ring in the Ordovician . . 646 . 118991 . 10.1016/j.epsl.2024.118991 . free.