Editing Impact event (section)

== Impacts and the Earth ==
{{Earth_Impact_Database_world_map.svg|upright=1.2}}
{{see also|List of impact structures on Earth}}
Major impact events have significantly shaped [[History of the Earth|Earth's history]], having been implicated in the [[giant impact theory|formation of the Earth–Moon system]], the [[evolutionary history of life]], the [[origin of water on Earth]], and several [[mass extinction]]s. [[Impact structure]]s are the result of impact events on solid objects and, as the dominant landforms on many of the System's solid objects, present the most solid evidence of prehistoric events. Notable impact events include the hypothesized [[Late Heavy Bombardment]], which would have occurred early in the history of the Earth–Moon system, and the confirmed [[Chicxulub impact]] 66 million years ago, believed to be the cause of the [[Cretaceous–Paleogene extinction event]].

=== Frequency and risk ===
{{Main|Asteroid impact avoidance}}
{{wide image|SmallAsteroidImpacts-Frequency-Bolide-20141114.jpg|500px|align-cap=center|Frequency of small asteroids roughly 1 to 20 meters in diameter impacting Earth's atmosphere.}}
[[File:Bolide.jpg|thumb|A bolide undergoing atmospheric entry]]

Small objects frequently collide with Earth. There is an [[inverse relationship]] between the size of the object and the frequency of such events. The lunar cratering record shows that the frequency of impacts decreases as approximately the [[cube (algebra)|cube]] of the resulting crater's diameter, which is on average proportional to the diameter of the impactor.<ref name=ArvidsonEtAl79>{{Citation|last1=Crater Analysis Techniques Working Group|title=Standard Techniques for Presentation and Analysis of Crater Size-Frequency Data|journal=Icarus|volume=37|issue=2|pages=467–474|date=1979| postscript=.|bibcode=1979Icar...37..467C | doi = 10.1016/0019-1035(79)90009-5|last2=Arvidson| first2=R. E. |last3=Boyce|first3=J. |last4=Chapman|first4=C. |last5=Cintala|first5=M. |last6=Fulchignoni |first6=M.|last7=Moore|first7=H.|last8=Neukum|first8=G.|last9=Schultz |first9=P. |last10=Soderblom |first10=L.|last11=Strom|first11=R. |last12=Woronow |first12=A. |last13=Young|first13=R.|hdl=2060/19780014063|s2cid=118171810 |hdl-access=free}}</ref> Asteroids with a {{convert|1|km|mi|abbr=on}} diameter strike Earth every 500,000 years on average.<ref name="Paine 2002">{{Cite journal|last1=Paine|first1=Michael|last2=Peiser|first2=Benny|date=2002|title=The Frequency and Consequences of Cosmic Impacts Since the Demise of the Dinosaurs|url=https://www.researchgate.net/publication/265496068|journal=Bioastronomy 2002: Life Among the Stars}}</ref><ref name="types">{{Citation |author-link=Nick Bostrom |first=Nick |last=Bostrom |date=March 2002 |url=http://www.nickbostrom.com/existential/risks.html |title=Existential Risks: Analyzing Human Extinction Scenarios and Related Hazards |journal=Journal of Evolution and Technology |volume=9}}</ref> Large collisions – with {{convert|5|km|mi|0|abbr=on}} objects – happen approximately once every twenty million years.<ref name="Earth-impact" /> The last known impact of an object of {{convert|10|km|mi|0|abbr=on}} or more in diameter was at the Cretaceous–Paleogene extinction event 66 million years ago.<ref name="UCB2013" />

The energy released by an impactor depends on diameter, density, velocity, and angle.<ref name="Earth-impact" /> The diameter of most near-Earth asteroids that have not been studied by radar or infrared can generally only be estimated within about a factor of two, by basing it on the asteroid's brightness. The density is generally assumed, because the diameter and mass, from which density can be calculated, are also generally estimated. Due to [[Earth escape velocity|Earth's escape velocity]], the minimum impact velocity is [[Earth escape velocity|11 km/s]] with asteroid impacts averaging around 17&nbsp;km/s on the Earth.<ref name="Earth-impact" /> The most probable impact angle is 45 degrees.<ref name="Earth-impact" />

Impact conditions such as asteroid size and speed, but also density and impact angle determine the kinetic energy released in an impact event. The more energy is released, the more damage is likely to occur on the ground due to the environmental effects triggered by the impact. Such effects can be shock waves, heat radiation, the formation of craters with associated earthquakes, and tsunamis if bodies of water are hit. Human populations are vulnerable to these effects if they live within the affected zone.<ref name="Rumpf 3433–3440"/> Large [[seiche wave]]s arising from earthquakes and large-scale deposit of debris can also occur within minutes of impact, thousands of kilometres from impact.<ref name=pnas1>[https://www.pnas.org/content/early/2019/03/27/1817407116 A seismically induced onshore surge deposit at the KPg boundary, North Dakota] {{Webarchive|url=https://web.archive.org/web/20190404144219/https://www.pnas.org/content/early/2019/03/27/1817407116 |date=2019-04-04 }} – Proceedings of the National Academy of Sciences – [[Robert DePalma]] ''et al.'', published 1 April 2019.<p>([https://www.pnas.org/content/pnas/early/2019/03/27/1817407116.full.pdf PDF direct link], [https://www.pnas.org/content/pnas/suppl/2019/03/27/1817407116.DCSupplemental/pnas.1817407116.sapp.pdf Supplementary published information])</p></ref>

==== Airbursts ====

{{Further|Meteor air burst}}

Stony asteroids with a diameter of {{convert|4|m|sp=us}} enter Earth's atmosphere about once a year.<ref name="Earth-impact" /> Asteroids with a diameter of 7 meters enter the atmosphere about every 5 years with as much [[kinetic energy]] as [[Atomic bombings of Hiroshima and Nagasaki|the atomic bomb dropped on Hiroshima]] (approximately 16 [[kiloton]]s of TNT), but the [[air burst]] is reduced to just 5 kilotons.<ref name="Earth-impact" /> These ordinarily explode in the [[Mesosphere|upper atmosphere]] and most or all of the solids are [[Evaporation|vaporized]].<ref>{{Citation|author = Clark R. Chapman & David Morrison|title = Impacts on the Earth by asteroids and comets: assessing the hazard|journal = Nature|volume =367|issue = 6458|pages=33–40|date=January 6, 1994|bibcode = 1994Natur.367...33C|doi = 10.1038/367033a0|last2 = Morrison|s2cid = 4305299|url = https://zenodo.org/record/1233151}}</ref> However, asteroids with a diameter of {{convert|20|m|abbr=on|lk=off}}, and which strike Earth approximately twice every century, produce more powerful airbursts. The 2013 Chelyabinsk meteor was estimated to be about 20 m in diameter with an airburst of around 500 kilotons, an explosion 30 times the Hiroshima bomb impact. Much larger objects may impact the solid earth and create a crater.

{| class="wikitable floatleft" style="text-align: center;"
|+Stony asteroid impacts that generate an airburst<ref name="Earth-impact" />
|-
! rowspan=2 | Impactor<br>diameter !! colspan=2 | [[Kinetic energy]] at !! rowspan=2 | Airburst<br>altitude !! rowspan=2 | Average<br>frequency<br>(years) !! rowspan=2 | Recorded fireballs<br>(CNEOS)<br>(1988–2018)
|-
! atmospheric<br>entry
! [[air burst|airburst]]
|-
| {{convert|4|m|abbr=on|lk=on}} || 3 [[TNT equivalent|kt]] || 0.75 kt || {{convert|42.5|km|ft||abbr=on|lk=on}} || 1.3 || 54
|-
| {{convert|7|m|abbr=on|lk=off}} || [[Little Boy|16 kt]] || 5 kt || {{convert|36.3|km|ft||abbr=on|lk=off}} || 4.6 || 15
|-
| {{convert|10|m|abbr=on|lk=off}} || 47 kt || [[Fat Man|19 kt]] || {{convert|31.9|km|ft||abbr=on|lk=off}} || 10 || 2
|-
| {{convert|15|m|abbr=on|lk=off}} || 159 kt || [[W76|82 kt]] || {{convert|26.4|km|ft||abbr=on|lk=off}} || 27 || [[Kamchatka superbolide|'''1''']]
|-
| {{convert|20|m|abbr=on|lk=off}} || 376 kt || [[TN 81|230 kt]] || {{convert|22.4|km|ft||abbr=on|lk=off}} || 60 || [[Chelyabinsk meteor|'''1''']]
|-
| {{convert|30|m|abbr=on|lk=off}} || [[B83 nuclear bomb|1.3]] [[TNT equivalent|Mt]] || 930 kt || {{convert|16.5|km|ft||abbr=on|lk=off}} || 185 || 0
|-
| {{convert|50|m|abbr=on|lk=off}} || 5.9 Mt || 5.2 Mt || {{convert|8.7|km|ft||abbr=on|lk=off}} || 764 || 0
|-
| {{convert|70|m|abbr=on|lk=off}} || 16 Mt || [[Castle Bravo|15.2 Mt]] || {{convert|3.6|km|ft||abbr=on|lk=off}} || 1,900 || 0
|-
| {{convert|85|m|abbr=on|lk=off}} || 29 Mt || 28 Mt || {{convert|0.58|km|ft||abbr=on|lk=off}} || 3,300 || 0
|-
! colspan=6 style="font-size: 0.9em; font-weight: normal; text-align: left; padding: 6px;"| Based on density of 2600&nbsp;kg/m<sup>3</sup>, speed of 17&nbsp;km/s, and an impact angle of 45°
|}

{| class="wikitable" style="text-align:center; float:left; margin-top:0;"
|+Stony asteroids that impact sedimentary rock and create a crater<ref name="Earth-impact" />
|-
! rowspan=2 | Impactor<br>diameter !! colspan=2 | [[Kinetic energy]] at !! rowspan=2 | [[Impact crater|Crater]]<br>diameter !! rowspan=2 | Frequency<br>(years)
|-
! [[Atmospheric entry|atmospheric<br>entry]]
! impact
|-
| {{convert|100|m|abbr=on|lk=on}} || 47 [[TNT equivalent|Mt]] || 3.4 Mt || {{convert|1.2|km|abbr=on|lk=on}} || 5,200
|-
| {{convert|130|m|abbr=on|lk=off}} || 103 Mt || 31.4 Mt || {{convert|2|km|abbr=on|lk=off}} || 11,000
|-
| {{convert|150|m|abbr=on|lk=off}} || 159 Mt || 71.5 Mt || {{convert|2.4|km|abbr=on|lk=off}} || 16,000
|-
| {{convert|200|m|abbr=on|lk=off}} || 376 Mt || 261 Mt || {{convert|3|km|abbr=on|lk=off}} || 36,000
|-
| {{convert|250|m|abbr=on|lk=off}} || 734 Mt || 598 Mt || {{convert|3.8|km|abbr=on|lk=off}} || 59,000
|-
| {{convert|300|m|abbr=on|lk=off}} || 1270 Mt || 1110 Mt || {{convert|4.6|km|abbr=on|lk=off}} || 73,000
|-
| {{convert|400|m|abbr=on|lk=off}} || 3010 Mt || 2800 Mt || {{convert|6|km|abbr=on|lk=off}} || 100,000
|-
| {{convert|700|m|abbr=on|lk=off}} || 16100 Mt || 15700 Mt || {{convert|10|km|abbr=on|lk=off}} || 190,000
|-
| {{convert|1000|m|abbr=on|lk=off}} || 47000 Mt || 46300 Mt || {{convert|13.6|km|abbr=on|lk=off}} || 440,000
|-
! colspan=5 style="font-size: 0.9em; font-weight: normal; text-align: left; padding: 6px;" | Based on [[Density|ρ]] = 2600&nbsp;kg/m<sup>3</sup>; [[Speed|v]] = 17&nbsp;km/s; and an angle of 45°
|}
{{clear|left}}

Objects with a diameter less than {{convert|1|m|ft|abbr=on}} are called [[meteoroids]] and seldom make it to the ground to become meteorites. An estimated 500 meteorites reach the surface each year, but only 5 or 6 of these typically create a [[weather radar]] signature with a [[strewn field]] large enough to be recovered and be made known to scientists.

The late [[Eugene Shoemaker]] of the [[United States Geological Survey|U.S. Geological Survey]] estimated the rate of Earth impacts, concluding that an event about the size of the nuclear weapon that destroyed [[Hiroshima]] occurs about once a year.{{citation needed|date=December 2013}} Such events would seem to be spectacularly obvious, but they generally go unnoticed for a number of reasons: the majority of the Earth's surface is covered by water; a good portion of the land surface is uninhabited; and the explosions generally occur at relatively high altitude, resulting in a huge flash and thunderclap but no real damage.{{citation needed|date=December 2013}}

Although no human is known to have been killed directly by an impact{{Disputed inline|.22Although_no_human_is_known_to_have_been_killed_directly_by_an_impact.22_-_not_true|date=January 2017}}, over 1000 people were injured by the Chelyabinsk meteor airburst event over Russia in 2013.<ref>["Число пострадавших при падении метеорита приблизилось к 1500" (in Russian). РосБизнесКонсалтинг. Retrieved 25 February 2013.]</ref> In 2005 it was estimated that the chance of a single person born today dying of an impact is around 1 in 200,000.<ref>{{cite web |url=https://www.newscientist.com/article/mg18825221.900-the-word-torino-scale.html |title=The word: Torino scale |work=[[New Scientist]] |page=56 |date=25 October 2005}}</ref> The two to four-meter-sized asteroids {{mpl|2008 TC|3}}, {{mpl|2014 AA}}, [[2018 LA]], [[2019 MO]], [[2022 EB5]], and the suspected artificial satellite [[WT1190F]] are the only known objects to be detected before impacting the Earth.<ref>[Roylance, Frank (2008-10-07). "Predicted meteor may have been sighted". MarylandWeather. Archived from the original on 10 October 2008. Retrieved 2008-10-08.]</ref><ref>{{cite web |title=The First Discovered Asteroid of 2014 Collides With The Earth – An Update |publisher=NASA/JPL |date=3 January 2014 |url=http://neo.jpl.nasa.gov/news/news182a.html |access-date=11 January 2014 |archive-date=11 February 2017 |archive-url=https://web.archive.org/web/20170211170917/http://neo.jpl.nasa.gov/news/news182a.html |url-status=dead }}</ref><ref>{{cite web|url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2022%20EB5&view=VOP |title=Small-Body Database Lookup |publisher=Ssd.jpl.nasa.gov |date= |accessdate=2022-03-16}}</ref>

=== Geological significance ===
Impacts have had, during the history of the Earth, a significant geological and climatic influence.<ref>French, B. M. (1998). Traces of catastrophe: A handbook of shock-metamorphic effects in terrestrial meteorite impact structures.</ref><ref>{{cite journal |last1=Alvarez |first1=L.W. |last2=Alvarez |first2=W. |last3=Asaro |first3=F. |last4=Michel |first4=H. V. |year=1980 |title=Extraterrestrial cause for the Cretaceous–Tertiary extinction |journal=Science |volume=208 |issue=4448 |pages=1095–1108 |bibcode=1980Sci...208.1095A |doi=10.1126/science.208.4448.1095 |pmid=17783054|citeseerx=10.1.1.126.8496 |s2cid=16017767 }}</ref>

The [[Moon]]'s existence is widely attributed to a [[Giant impact hypothesis|huge impact early in Earth's history]].<ref name=nature412>{{cite journal|last1=Canup |first1=R. |author1-link=Robin Canup |last2=Asphaug |first2=E. |title=Origin of the Moon in a giant impact near the end of the Earth's formation |journal=Nature |volume=412 |pages=708–712 |date=2001 |doi=10.1038/35089010 |pmid=11507633 |issue=6848 |bibcode=2001Natur.412..708C |s2cid=4413525 |url=http://www.es.ucsc.edu/~rcoe/eart206/canup_Moon_Nature_01.pdf |access-date=2011-12-10 |url-status=dead |archive-url=https://web.archive.org/web/20100730135923/http://es.ucsc.edu/~rcoe/eart206/canup_Moon_Nature_01.pdf |archive-date=July 30, 2010 }}</ref> Impact events earlier in the [[history of Earth]] have been credited with creative as well as destructive events; it has been proposed that impacting comets delivered the Earth's water, and some have suggested that the [[origins of life]] may have been influenced by impacting objects by bringing organic chemicals or lifeforms to the Earth's surface, a theory known as [[Panspermia|exogenesis]].

[[File:Eugene Shoemaker.jpg|thumb|upright|[[Eugene Merle Shoemaker]] was first to prove that [[meteorite]] impacts have affected the Earth.]]

These modified views of Earth's history did not emerge until relatively recently, chiefly due to a lack of direct observations and the difficulty in recognizing the signs of an Earth impact because of erosion and weathering. Large-scale terrestrial impacts of the sort that produced the [[Barringer Crater]], locally known as [[Meteor Crater]], east of Flagstaff, Arizona, are rare. Instead, it was widely thought that cratering was the result of [[volcanism]]: the Barringer Crater, for example, was ascribed to a prehistoric volcanic explosion (not an unreasonable hypothesis, given that the volcanic [[San Francisco Peaks]] stand only {{convert|30|mi|km|order=flip|abbr=on|disp=or}} to the west). Similarly, the craters on the surface of the Moon were ascribed to volcanism.

It was not until 1903–1905 that the Barringer Crater was correctly identified as an impact crater, and it was not until as recently as 1963 that research by [[Eugene Merle Shoemaker]] conclusively proved this hypothesis. The findings of late 20th-century [[space exploration]] and the work of scientists such as Shoemaker demonstrated that impact cratering was by far the most widespread geological process at work on the Solar System's solid bodies. Every surveyed solid body in the Solar System was found to be cratered, and there was no reason to believe that the Earth had somehow escaped bombardment from space. In the last few decades of the 20th century, a large number of highly modified impact craters began to be identified. The first direct observation of a major impact event occurred in 1994: the collision of the [[comet Shoemaker-Levy 9]] with [[Jupiter]].

Based on crater formation rates determined from the Earth's closest celestial partner, the Moon, [[astrogeology|astrogeologists]] have determined that during the last 600 million years, the Earth has been struck by 60 objects of a diameter of {{convert|5|km|mi|0|abbr=on}} or more.<ref name="Paine 2002" /> The smallest of these impactors would leave a crater almost {{convert|100|km|mi|-1|abbr=on}} across. Only three confirmed craters from that time period with that size or greater have been found: [[Chicxulub crater|Chicxulub]], [[Popigai impact structure|Popigai]], and [[Manicouagan Reservoir|Manicouagan]], and all three have been suspected of being linked to [[extinction events]]<ref>{{cite web|title=Russia's Popigai Meteor Crash Linked to Mass Extinction
 |website=[[Live Science]]
 |url=http://www.livescience.com/46312-popigai-crater-linked-eocene-mass-extinction.html
 |date=June 13, 2014}}</ref><ref>{{cite journal|first=J.P.|last=Hodych|author2=G.R.Dunning
 |title=Did the Manicouagan impact trigger end-of-Triassic mass extinction?
 |journal=Geology|volume=20|issue=1|date=1992|pages=51.54|doi=10.1130/0091-7613(1992)020<0051:DTMITE>2.3.CO;2|bibcode = 1992Geo....20...51H}}</ref> though only Chicxulub, the largest of the three, has been consistently considered. The impact that caused [[Mistastin crater]] generated temperatures exceeding 2,370&nbsp;°C, the highest known to have occurred on the surface of the Earth.<ref name="Gizmodo 2017-09-17">{{cite news |last=Dvorsky |first=George
 |url=https://www.gizmodo.com.au/2017/09/the-hottest-known-temperature-on-earth-was-caused-by-an-ancient-asteroid-strike/
 |title=The Hottest Known Temperature On Earth Was Caused By An Ancient Asteroid Strike
 |language=en |work=Gizmodo |date=2017-09-17 |access-date=2017-09-17}}</ref>

Besides the direct effect of asteroid impacts on a planet's surface topography, global climate and life, recent studies have shown that several consecutive impacts might have an effect on the [[dynamo mechanism]] at a planet's core responsible for maintaining the [[magnetic field of celestial bodies|magnetic field of the planet]], and may have contributed to Mars' lack of current magnetic field.<ref>{{Cite web|url=https://www.wired.com/2011/01/mars-dynamo-death/|archiveurl=https://web.archive.org/web/20131230034219/http://www.wired.com/wiredscience/2011/01/mars-dynamo-death/|url-status=dead|title=Multiple Asteroid Strikes May Have Killed Mars's Magnetic Field|first=Lisa|last=Grossman|archivedate=December 30, 2013|via=www.wired.com}}</ref> An impact event may cause a [[mantle plume]] ([[Antipodal hotspot|volcanism]]) at the [[antipodal point]] of the impact.<ref name="Hagstrum 2005">{{Cite journal|last1=Hagstrum|first1=Jonathan T.|date=2005|title=Antipodal Hotspots and Bipolar Catastrophes: Were Oceanic Large-body Impacts the Cause?|url=http://www.mantleplumes.org/WebDocuments/Antip_hot.pdf|journal=[[Earth and Planetary Science Letters]]|volume=236|issue=1–2|pages=13–27|bibcode=2005E&PSL.236...13H|doi=10.1016/j.epsl.2005.02.020}}</ref> The Chicxulub impact may have increased volcanism at [[mid-ocean ridge]]s<ref>{{Cite journal|last1=Byrnes|first1=Joseph S.|last2=Karlstrom|first2=Leif|date=February 2018|title=Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism|journal=Science Advances|language=en|volume=4|issue=2|pages=eaao2994|doi=10.1126/sciadv.aao2994|issn=2375-2548|pmc=5810608|pmid=29441360|bibcode=2018SciA....4.2994B}}</ref> and has been proposed to have triggered [[Flood-basalt volcanism|flood basalt volcanism]] at the [[Deccan Traps]].<ref>{{Cite journal|last1=Richards|first1=Mark A.|last2=Alvarez|first2=Walter|last3=Self|first3=Stephen|last4=Karlstrom|first4=Leif|last5=Renne|first5=Paul R.|last6=Manga|first6=Michael|last7=Sprain|first7=Courtney J.|last8=Smit|first8=Jan|last9=Vanderkluysen|first9=Loÿc|last10=Gibson|first10=Sally A.|date=2015-11-01|title=Triggering of the largest Deccan eruptions by the Chicxulub impact|url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/127/11-12/1507/126064/Triggering-of-the-largest-Deccan-eruptions-by-the|journal=GSA Bulletin|language=en|volume=127|issue=11–12|pages=1507–1520|doi=10.1130/B31167.1|bibcode=2015GSAB..127.1507R|osti=1512141 |s2cid=3463018 |issn=0016-7606}}</ref>

While numerous impact craters have been confirmed on land or in the shallow seas over [[continental shelves]], no impact craters in the deep ocean have been widely accepted by the scientific community.<ref>{{cite journal|last1=Dypvik|first1=Henning|last2=Burchell|first2=Mark|last3=Claeys|first3=Philippe|title=Impacts into Marine and Icy Environments: A Short Review in ''Cratering in Marine Environments and on Ice''}}</ref> Impacts of projectiles as large as one&nbsp;km in diameter are generally thought to explode before reaching the sea floor, but it is unknown what would happen if a much larger impactor struck the deep ocean. The lack of a crater, however, does not mean that an ocean impact would not have dangerous implications for humanity. Some scholars have argued that an impact event in an [[ocean]] or [[sea]] may create a [[megatsunami]], which can cause destruction both at sea and on land along the coast,<ref name=GaultEtAl79>{{cite journal|last1=Gault|first1=D. E.|last2=Sonnet|first2=C. P.|last3=Wedekind|first3=J. A.|title=Tsunami Generation by Pelagic Planetoid Impact|journal=Lunar and Planetary Science Conference Abstract|date=1979}}</ref> but this is disputed.<ref name=Melosh03>{{cite journal|last=Melosh|first=H. J.|title=Impact-generated tsunamis: An over-rated hazard|journal=Lunar and Planetary Science Conference Abstract|volume=34|page=2013|date=2003|bibcode=2003LPI....34.2013M}}</ref> The [[Eltanin impact]] into the [[Pacific Ocean]] 2.5 Mya is thought to involve an object about {{convert|1|to|4|km}} across but remains craterless.

=== Biospheric effects ===
The effect of impact events on the biosphere has been the subject of scientific debate. Several theories of impact-related mass extinction have been developed. In the past 500 million years there have been five generally accepted <!-- there is some scientific disagreement over the number, so I have inserted the qualifier of common or "general acceptance" --> major mass extinctions that on average extinguished half of all [[species]].<ref name="Keller"/> One of the largest mass extinctions to have affected [[life|life on Earth]] was the [[Permian-Triassic extinction event|Permian-Triassic]], which ended the [[Permian]] period 250 million years ago and killed off 90 percent of all species;<ref>{{Cite web|url=https://math.ucr.edu/home/baez/extinction/|title=extinction|website=math.ucr.edu}}</ref> life on Earth took 30 million years to recover.<ref name="SahneyBenton2008RecoveryFromProfoundExtinction">{{Citation |url= |author1=Sahney, S. |author2=Benton, M.J. |date=2008 |title=Recovery from the most profound mass extinction of all time |pmid=18198148 |journal=Proceedings of the Royal Society B: Biological Sciences |pmc=2596898 |doi=10.1098/rspb.2007.1370 |volume=275 |issue=1636 |pages=759–765 }}</ref> The cause of the Permian-Triassic extinction is still a matter of debate; the age and origin of proposed impact craters, i.e. the [[Bedout]] High structure, hypothesized to be associated with it are still controversial.<ref name="Muller2005">{{cite journal | last1 = Müller | first1 = R.D. | last2 = Goncharov | first2 = A. | last3 = Kristi | first3 = A. | year = 2005 | title = Geophysical evaluation of the enigmatic Bedout basement high, offshore northwest Australia | journal = Earth and Planetary Science Letters | volume = 237 | issue = 1–2| pages = 265–284 | doi=10.1016/j.epsl.2005.06.014 | bibcode=2005E&PSL.237..264M}}</ref> The [[Cretaceous–Paleogene extinction event|last]] such mass extinction led to the demise of the non-avian [[dinosaur]]s and coincided with a large [[meteorite]] impact; this is the Cretaceous–Paleogene extinction event (also known as the K–T or K–Pg extinction event), which occurred 66 million years ago. There is no definitive evidence of impacts leading to the three other major mass extinctions.

In 1980, physicist [[Luis Walter Alvarez|Luis Alvarez]]; his son, geologist [[Walter Alvarez]]; and nuclear chemists Frank Asaro and Helen V. Michael from the [[University of California, Berkeley]] discovered unusually high concentrations of [[iridium]] in a specific layer of rock [[stratum|strata]] in the Earth's crust. Iridium is an element that is rare on Earth but relatively abundant in many meteorites. From the amount and distribution of iridium present in the 65-million-year-old "iridium layer", the Alvarez team later estimated that an asteroid of {{convert|10|to|14|km|mi|0|abbr=on}} must have collided with Earth. This iridium layer at the [[Cretaceous–Paleogene boundary]] has been found worldwide at 100 different sites. Multidirectionally [[shocked quartz]] (coesite), which is normally associated with large impact events<ref name=Fulgurite>{{cite journal|last1=Carter|first1=Elizabeth|last2=Pasek|first2=Matthew|last3=Smith|first3=Tim|last4=Kee|first4=Terence|last5=Hines|first5=Peter|last6=Howell|first6=G. M. Edwards|title=Rapid Raman mapping of a fulgurite (Paywall)|journal=Analytical and Bioanalytical Chemistry|date=August 2010|volume=397|issue=7|pages=2647–2658|doi=10.1007/s00216-010-3593-z|pmid=20229006|s2cid=23476732}}</ref> or [[atomic bomb]] explosions, has also been found in the same layer at more than 30 sites. [[Soot]] and [[wikt:ash|ash]] at levels tens of thousands times normal levels were found with the above.

Anomalies in chromium isotopic ratios found within the [[K-T boundary]] layer strongly support the impact theory.<ref name="Shukolyukov1998">{{Citation | last1 = Shukolyukov | first1 = A. | last2 = Lugmair | first2 = G. W. | date = 1998 | title = Isotopic Evidence for the Cretaceous-Tertiary Impactor and Its Type | journal = Science | volume = 282 | issue = 5390| pages = 927–930 | doi = 10.1126/science.282.5390.927 | postscript = . | pmid=9794759 | bibcode=1998Sci...282..927S}}</ref> Chromium isotopic ratios are homogeneous within the earth, and therefore these isotopic anomalies exclude a volcanic origin, which has also been proposed as a cause for the iridium enrichment. Further, the chromium isotopic ratios measured in the K-T boundary are similar to the chromium isotopic ratios found in [[carbonaceous chondrite]]s. Thus a probable candidate for the impactor is a carbonaceous asteroid, but a comet is also possible because comets are assumed to consist of material similar to carbonaceous chondrites.

Probably the most convincing evidence for a worldwide catastrophe was the discovery of the crater which has since been named [[Chicxulub Crater]]. This crater is centered on the Yucatán Peninsula of Mexico and was discovered by Tony Camargo and [[Glen Penfield]] while working as [[geophysicist]]s for the Mexican oil company [[PEMEX]].<ref>{{cite web|last=Penfield|first=December 2019 Glen|date=2019-12-01|title=Unlikely Impact|url=https://explorer.aapg.org/story/articleid/55293/unlikely-impact|access-date=2020-08-17|website=AAPG Explorer|language=en-US}}</ref> What they reported as a circular feature later turned out to be a crater estimated to be {{convert|180|km|mi|-1|abbr=on}} in diameter. This convinced the vast majority of scientists that this extinction resulted from a point event that is most probably an extraterrestrial impact and not from increased volcanism and climate change (which would spread its main effect over a much longer time period).

Although there is now general agreement that there was a huge impact at the end of the Cretaceous that led to the iridium enrichment of the K-T boundary layer, remnants have been found of other, smaller impacts, some nearing half the size of the Chicxulub crater, which did not result in any mass extinctions, and there is no clear linkage between an impact and any other incident of mass extinction.<ref name="Keller">{{cite journal | url=http://instruct.uwo.ca/earth-sci/083f/kellerkt.pdf | title=Impacts, volcanism and mass extinction: random coincidence or cause and effect? | author=Keller G. | journal=Australian Journal of Earth Sciences | date=2005 | volume=52 | issue=4–5 | pages=725–757 | doi=10.1080/08120090500170393|bibcode = 2005AuJES..52..725K | s2cid=39063747 }}</ref>

Paleontologists [[David M. Raup]] and [[Jack Sepkoski]] have proposed that an excess of extinction events occurs roughly every 26 million years (though many are relatively minor). This led physicist [[Richard A. Muller]] to suggest that these extinctions could be due to a hypothetical companion star to the Sun called [[Nemesis (hypothetical star)|Nemesis]] periodically disrupting the orbits of comets in the [[Oort cloud]], leading to a large increase in the number of comets reaching the inner Solar System where they might hit Earth. Physicist [[Adrian Melott]] and paleontologist [[Richard Bambach]] have more recently verified the Raup and Sepkoski finding, but argue that it is not consistent with the characteristics expected of a Nemesis-style periodicity.<ref>{{Citation|author = Adrian L. Melott & Richard K. Bambach|title = Nemesis Reconsidered|date=2010|journal = [[Monthly Notices of the Royal Astronomical Society Letters]]|volume =407|issue = 1|pages=L99–L102|arxiv = 1007.0437 |bibcode = 2010MNRAS.407L..99M |doi = 10.1111/j.1745-3933.2010.00913.x |last2 = Bambach| doi-access=free |s2cid = 7911150}}</ref>

=== Sociological and cultural effects ===
{{see also|End of civilization}}

An impact event is commonly seen as a scenario that would bring about the [[end of civilization]]. In 2000, [[Discover (magazine)|''Discover'' magazine]] published a list of 20 possible sudden [[doomsday event|doomsday scenarios]] with an impact event listed as the most likely to occur.<ref>[http://discovermagazine.com/2000/oct/featworld "Twenty ways the world could end suddenly"]. [[Discover (magazine)|''Discover'']].</ref>

A joint [[Pew Research Center]]/''[[Smithsonian magazine|Smithsonian]]'' survey from April 21 to 26, 2010 found that 31 percent of Americans believed that an asteroid will collide with Earth by 2050. A majority (61 percent) disagreed.<ref>{{Cite web|url=http://people-press.org/reports/pdf/625.pdf|title=Public sees a future full of promise and peril|access-date=2014-07-11|archive-date=2011-02-04|archive-url=https://web.archive.org/web/20110204080409/http://people-press.org/reports/pdf/625.pdf|url-status=bot: unknown}}</ref>

===Earth impacts===
[[File:Artist's concept of collision at HD 172555.jpg|thumb|Artist's depiction of a collision between two planetary bodies. Such an impact between the Earth and a Mars-sized object likely [[giant impact theory|formed the Moon]].]]
In the early history of the Earth (about four billion years ago), bolide impacts were almost certainly common since the Solar System contained far more discrete bodies than at present. Such impacts could have included strikes by asteroids hundreds of kilometers in diameter, with explosions so powerful that they vaporized all the Earth's oceans. It was not until this heavy bombardment slackened that life appears to have begun to evolve on Earth.

====Precambrian====
The leading theory of the Moon's origin is the giant impact theory, which postulates that Earth was once hit by a [[Minor planet|planetoid]] the size of Mars; such a theory is able to explain the size and composition of the Moon, something not done by other theories of lunar formation.<ref>{{cite journal | title = Dynamics of Lunar Formation | author = Canup, Robin M. | journal = Annual Review of Astronomy & Astrophysics | volume = 42 | issue = 1 | pages = 441–475 | doi=10.1146/annurev.astro.41.082201.113457|bibcode = 2004ARA&A..42..441C | year = 2004 }}</ref>

According to the theory of the [[Late Heavy Bombardment]], there should have been 22,000 or more impact craters with diameters >20&nbsp;km (12&nbsp;mi), about 40 impact basins with diameters about 1,000&nbsp;km (620&nbsp;mi), and several impact basins with diameters about 5,000&nbsp;km (3,100&nbsp;mi). However, hundreds of millions of years of deformation at the Earth's crust pose significant challenges to conclusively identifying impacts from this period. Only two pieces of pristine [[lithosphere]] are believed to remain from this era: [[Kaapvaal craton]] (in contemporary South Africa) and [[Pilbara craton|Pilbara Craton]] (in contemporary Western Australia) to search within which may potentially reveal evidence in the form of physical craters. Other methods may be used to identify impacts from this period, for example, indirect gravitational or magnetic analysis of the mantle, but may prove inconclusive.

In 2021, evidence for a probable impact 3.46 billion-years ago at Pilbara Craton has been found in the form of a {{convert|150|km|mi}} crater created by the impact of a {{convert|10|km|mi}} asteroid (named "The Apex Asteroid") into the sea at a depth of {{convert|2.5|km|mi}} (near the site of [[Marble Bar, Western Australia]]).<ref name="Ohmoto Graham Liu Tsukamoto p.">{{citation | last1=Ohmoto | first1=Hiroshi | last2=Graham | first2=Uschi | last3=Liu | first3=Zi-Kui | last4=Tsukamoto | first4=Yuya | last5=Watanabe | first5=Yumiko | last6=Hamasaki | first6=Hiroshi | last7=Chorney | first7=Andrew | title=Discovery of a 3.46 billion-year-old impact crater in Western Australia | journal=Ess Open Archive ePrints | publisher=Wiley | date=2021-01-16 | volume=105 | doi=10.1002/essoar.10505838.1 | page=| bibcode=2021esoar.10505838O | s2cid=234265636 }}</ref> The event caused global tsunamis. It is also coincidental to some of the earliest evidence of life on Earth, fossilized [[Stromatolite]]s.

Evidence for at least 4 impact events have been found in spherule layers (dubbed S1 through S8)  from the [[Barberton Greenstone Belt]] in South Africa, spanning around 3.5-3.2 billion years ago.<ref>{{Cite journal |last1=Ozdemir |first1=Seda |last2=Schulz |first2=Toni |last3=Koeberl |first3=Christian |last4=Reimold |first4=Wolf Uwe |last5=Mohr-Westheide |first5=Tanja |last6=Hoehnel |first6=Desiree |last7=Schmitt |first7=Ralf Thomas |date=27 November 2017 |title=Early Archean spherule layers from the Barberton Greenstone Belt, South Africa: Mineralogy and geochemistry of the spherule beds in the CT 3 drill core |journal=Meteoritics & Planetary Science |language=en |volume=52 |issue=12 |pages=2586–2631 |doi=10.1111/maps.12998 |issn=1086-9379|doi-access=free |bibcode=2017M&PS...52.2586O }}</ref> The sites of the impacts are thought to have been distant from the location of the belt. The impactors that generated these events are thought to have been much larger than those that created the largest known still existing craters/impact structures on Earth, with the impactors having estimated diameters of ~{{Convert|20-50|km|mi}}, with the craters generated by these impacts having an estimated diameter of {{Convert|400-1000|km|mi}}.<ref>{{Cite journal |last1=Lowe |first1=Donald R. |last2=Byerly |first2=Gary R. |date=April 2018 |title=The terrestrial record of Late Heavy Bombardment |url=https://linkinghub.elsevier.com/retrieve/pii/S1387647317300714 |journal=New Astronomy Reviews |language=en |volume=81 |pages=39–61 |doi=10.1016/j.newar.2018.03.002|bibcode=2018NewAR..81...39L }}</ref> The largest impacts like those represented by the S2 layer are likely to have had far-reaching effects, such as the boiling of the surface layer of the oceans.<ref name="10.1073/pnas.2408721121PNAS">{{cite journal |last1=Drabon |first1=Nadja |last2=Knoll |first2=Andrew H. |last3=Lowe |first3=Donald R. |date=21 October 2024 |title=Effect of a giant meteorite impact on Paleoarchean surface environments and life. |journal=PNAS |volume=121 |issue=44 |pages= e2408721121|doi=10.1073/pnas.2408721121 |pmid=39432780 |pmc=11536127 }}</ref>

The [[Maniitsoq structure]], dated to around 3 billion years old (3 Ga), was once thought to be the result of an impact;<ref name="garde 2012">{{cite journal |last1=Garde |first1=Adam A. |last2=McDonald |first2=Iain |last3=Dyck |first3=Brendan |last4=Keulen |first4=Nynke |title=Searching for giant, ancient impact structures on Earth: The Mesoarchaean Maniitsoq structure, West Greenland |journal=Earth and Planetary Science Letters |date=July 2012 |volume=337–338 |pages=197–210 |doi=10.1016/j.epsl.2012.04.026|bibcode=2012E&PSL.337..197G }}</ref><ref name=":1">{{Cite journal|last=Wolf U. Reimold, Roger L. Gibson, Christian Koeberl|date=2013|title=Comment on "Searching for giant, ancient impact structures on Earth: The Mesoarchaean Maniitsoq structure, West Greenland" by Garde et al.|url=https://doi.org/10.1016/j.epsl.2013.04.014|journal=Earth and Planetary Science Letters|volume=369–370|pages=333–335|doi=10.1016/j.epsl.2013.04.014|via=Elsevier Science Direct|url-access=subscription}}</ref> however, follow-up studies have not confirmed its nature as an impact structure.<ref name=":1" /><ref name=":2">{{Cite journal|last=Wolf U. Reimold, Ludovic Ferrière, Alex Deutsch, Christian Koeberl|date=2014|title=Impact controversies: Impact recognition criteria and related issues|journal=Meteoritics and Planetary Science|volume=49|issue=5|pages=723–731|doi=10.1111/maps.12284|bibcode=2014M&PS...49..723R|s2cid=128625029|doi-access=free}}</ref><ref name=":3">{{Cite journal|last=C. L. Kirkland, C. Yakymchuk, J. Hollis, H. Heide-Jørgensen, M. Danišík|date=2018|title=Mesoarchean exhumation of the Akia terrane and a common Neoarchean tectonothermal history for West Greenland|journal=Precambrian Research|volume=314|pages=129–144|doi=10.1016/j.precamres.2018.06.004|bibcode=2018PreR..314..129K|s2cid=135213870|doi-access=free}}</ref><ref name=":5">{{Cite journal|last=N. J. Gardiner, C. L. Kirkland, J. Hollis, K. Szilas, A. Steenfelt, C. Yakymchuk, H. Heide-Jørgensen|date=2019|title=Building Mesoarchaean crust upon Eoarchaean roots: the Akia Terrane, West Greenland|journal=Contributions to Mineralogy and Petrology|volume=174|issue=3|page=20|doi=10.1007/s00410-019-1554-x|bibcode=2019CoMP..174...20G|s2cid=134027320|doi-access=free|hdl=10023/18486|hdl-access=free}}</ref><ref name=":6">{{Cite journal|last=C. Yakymchuk, C. L. Kirkland, J. A. Hollis, J. Kendrick, N. J. Gardiner, K. Szilas|date=2020|title=Mesoarchean partial melting of mafic crust and tonalite production during high-T–low-P stagnant tectonism, Akia Terrane, West Greenland|journal=Precambrian Research|volume=339|page=105615|doi=10.1016/j.precamres.2020.105615|bibcode=2020PreR..33905615Y|s2cid=213973363|doi-access=free|hdl=10023/19439|hdl-access=free}}</ref><ref name=":4">{{Cite journal|last=Pedro Waterton, William R. Hyde, Jonas Tusch, Julie A. Hollis, Christopher L. Kirkland, Carson Kinney, Chris Yakymchuk, Nicholas J. Gardiner, David Zakharov, Hugo K. H. Olierook, Peter C. Lightfoot, Kristoffer Szilas|date=2020|title=Geodynamic Implications of Synchronous Norite and TTG Formation in the 3 Ga Maniitsoq Norite Belt, West Greenland|journal=Frontiers in Earth Science|volume=8|page=562062|doi=10.3389/feart.2020.562062|bibcode=2020FrEaS...8..406W|doi-access=free|hdl=10023/20744|hdl-access=free}}</ref> The Maniitsoq structure is not recognised as an impact structure by the [[Earth Impact Database]].<ref name=":9">{{cite web|title=Earth Impact Database|url=http://www.passc.net/EarthImpactDatabase/New%20website_05-2018/Index.html|access-date=2020-09-30|website=www.passc.net}}</ref>

In 2020, scientists discovered the world's oldest confirmed impact crater, the [[Yarrabubba crater]], caused by an impact that occurred in [[Yilgarn craton]] (what is now [[Western Australia]]), dated at more than 2.2 billion years ago with the impactor estimated to be around {{convert|7|km|mi}} wide.<ref name="NYT-20200121">{{cite news |last=Kornel |first=Katherine |title=Earth's Oldest Asteroid Impact Found in Australia – The cataclysm, which occurred roughly 2.2 billion years ago, might have catapulted the planet out of an ice age. |url=https://www.nytimes.com/2020/01/21/science/oldest-asteroid-impact-australia.html |date=21 January 2020 |work=[[The New York Times]] |access-date=22 January 2020 }}</ref><ref name="NC-20200121">{{cite journal |author=Erikson, Timmons M. |display-authors=et al. |title=Precise radiometric age establishes Yarrabubba, Western Australia, as Earth's oldest recognised meteorite impact structure |date=21 January 2020 |journal=[[Nature Communications]] |volume=11 |issue=300 |page=300 |doi=10.1038/s41467-019-13985-7 |pmid=31964860 |pmc=6974607 |bibcode=2020NatCo..11..300E }}</ref><ref name=erickson>{{cite journal |author1=Erickson, T.M.|author2= Kirkland, C.L.|author3= Timms, N.E.|author4= Cavosie, A.J.|author5= Davison, T.M. |title=Precise radiometric age establishes Yarrabubba, Western Australia, as Earth's oldest recognised meteorite impact structure |journal=Nature Communications |date=21 Jan 2020 |volume=11 |issue=300 |page= 300|doi=10.1038/s41467-019-13985-7|pmid= 31964860|pmc= 6974607|bibcode=2020NatCo..11..300E }}</ref> It is believed that, at this time, the Earth was mostly or completely frozen, commonly called the [[Huronian glaciation]].

The [[Vredefort impact structure|Vredefort impact event]], which occurred around 2 billion years ago in [[Kaapvaal craton]] (what is now [[South Africa]]), caused the largest verified crater, a multi-ringed structure {{convert|160|-|300|km|mi|abbr=on|sigfig=1}} across, forming from an impactor approximately {{convert|10|–|15|km|abbr=on}} in diameter.<ref name="DB">{{Cite Earth Impact DB | name = Vredefort | access-date = 2008-12-30}}</ref><ref name="current record">{{cite web| title = Deep Impact – The Vredefort Dome| url=http://www.hartrao.ac.za/other/vredefort/vredefort.html| publisher= [[Hartebeesthoek Radio Astronomy Observatory]]| access-date = 2007-09-19| date = 2006-08-01}}</ref>

The [[Sudbury Basin|Sudbury impact event]] occurred on the [[Columbia (supercontinent)|Nuna supercontinent]] (now [[Canada]]) from a bolide approximately {{convert|10|-|15|km|mi|abbr=on}} in diameter approximately 1.849 billion years ago<ref name=Davis>{{cite journal|last=Davis| first= Donald W. | date= January 23, 2008| title= Sub-million-year age resolution of Precambrian igneous events by thermal extraction-thermal ionization mass spectrometer Pb dating of zircon: Application to crystallization of the Sudbury impact melt sheet| journal= Geology|  volume = 36| number = 5| pages= 383–386 |doi= 10.1130/G24502A.1| bibcode= 2008Geo....36..383D}}</ref> Debris from the event would have been scattered across the globe.

====Paleozoic and Mesozoic====
Two {{convert|10|km||adj=mid| sized}} asteroids are now believed to have struck Australia between 360 and 300 million years ago at the [[West Warburton Basin|Western Warburton]] and [[East Warburton Basin]]s, creating a {{convert|400|km||adj=mid| impact zone}}. According to evidence found in 2015, it is the largest ever recorded.<ref>{{Cite web|url=https://www.australiangeographic.com.au/news/2015/03/worlds-largest-asteroid-impact-found-in-australia/|title=World's largest asteroid impact found in Australia|date=March 24, 2015|website=Australian Geographic}}</ref> A [[Diamantina River ring feature|third, possible impact]] was also identified in 2015 to the north, on the upper [[Diamantina River]], also believed to have been caused by an asteroid 10&nbsp;km across about 300 million years ago, but further studies are needed to establish that this crustal anomaly was indeed the result of an impact event.<ref>{{cite web|url=http://www.ga.gov.au/news-events/news/latest-news/potential-asteroid-impact-identified-in-western-queensland|title=Potential asteroid impact identified in western Queensland|publisher=Geoscience Australia|access-date=26 June 2016|date=2015-03-17}}</ref>

[[File:Chicxulub-animation.gif|thumb|An animation modelling the impact, and subsequent crater formation of the Chicxulub impact (University of Arizona, Space Imagery Center)]]
The prehistoric [[Chicxulub crater#Impact specifics|Chicxulub impact]], 66 million years ago, believed to be the cause of the Cretaceous–Paleogene extinction event, was caused by an asteroid estimated to be about {{convert|10|km|mi}} wide.<ref name="autogenerated76"/>


==== Paleogene ====
[[File:Hiawatha v45 scene1 4k 5mtopo.1760.tif|thumb|The Hiawatha impact crater in Greenland is buried under more than a kilometre of ice]]
Analysis of the [[Hiawatha Glacier]] reveals the presence of a 31&nbsp;km wide impact crater dated at 58 million years of age, less than 10 million years after the Cretaceous–Paleogene extinction event, scientists believe that the impactor was a metallic asteroid with a diameter in the order of 1.5 kilometres (0.9&nbsp;mi). The impact would have had global effects.<ref name="InitialStudy">{{cite journal|first=Kurt H. |last=Kjær |display-authors=et al |doi=10.1126/sciadv.aar8173|pmid=30443592 |pmc=6235527 |title=A large impact crater beneath Hiawatha Glacier in northwest Greenland|journal=Science Advances |volume=4 |issue=11 |pages=eaar8173 |date=November 2018 |bibcode=2018SciA....4.8173K }}</ref>

==== Pleistocene ====
{{Further|Pleistocene}}
[[File:Barringer Crater aerial photo by USGS.jpg|thumb|Aerial view of [[Barringer Crater]] in [[Arizona]]]]

[[Stone tools|Artifacts]] recovered with [[tektites]] from the 803,000-year-old [[Australasian strewnfield]] event in Asia link a ''[[Homo erectus]]'' population to a significant meteorite impact and its aftermath.<ref>{{Cite web|url=http://humanorigins.si.edu/evidence/behavior/stone-tools/early-stone-age-tools/handaxe-and-tektites-bose-china|archiveurl=https://web.archive.org/web/20141008080600/https://humanorigins.si.edu/evidence/behavior/handaxe-and-tektites-bose-china|url-status=dead|title=Handaxe and Tektites from Bose, China|archivedate=October 8, 2014|website=The Smithsonian Institution's Human Origins Program}}</ref><ref>{{cite news| url=http://news.bbc.co.uk/2/hi/science/nature/664967.stm | work=BBC News | title=Asia's oldest axe tools discovered | date=March 3, 2000}}</ref><ref>{{Cite journal | doi=10.1146/annurev.anthro.33.070203.144024|title = Early Dispersals of Homo from Africa| journal=Annual Review of Anthropology| volume=33| pages=271–296|year = 2004|last1 = Antón|first1 = Susan C.| last2=Swisher, Iii| first2=Carl C.}}</ref> Significant examples of Pleistocene impacts include the [[Lonar crater lake]] in India, approximately 52,000 years old (though a study published in 2010 gives a much greater age), which now has a flourishing semi-tropical jungle around it.{{citation needed|date=February 2015}}
<!--The Younger Dryas impact hypothesis seems to be dead (2015) And, Younger Dryas is in Holocene, aka Modern Era --->

==== Holocene ====
{{Further|Holocene}}
The [[Rio Cuarto craters]] in Argentina were produced approximately 10,000 years ago, at the beginning of the Holocene. If proved to be impact craters, they would be the first impact of the Holocene.

The [[Campo del Cielo]] ("Field of Heaven") refers to an area bordering Argentina's [[Chaco Province]] where a group of iron meteorites were found, estimated as dating to 4,000–5,000 years ago. It first came to attention of Spanish authorities in 1576; in 2015, police arrested four alleged smugglers trying to steal more than a ton of protected meteorites.<ref>{{Cite web|url=http://news.yahoo.com/four-arrested-argentina-smuggling-more-ton-meteorites-210404348.html|title=Four arrested in Argentina smuggling more than ton of meteorites|website=news.yahoo.com}}</ref> The [[Henbury craters]] in Australia (~5,000 years old) and [[Kaali crater]]s in Estonia (~2,700 years old) were apparently produced by objects that broke up before impact.<ref>{{cite web | url=https://nt.gov.au/leisure/parks-reserves/find-a-park-to-visit/henbury-meteorites-conservation-reserve | title=Henbury Meteorites Conservation Reserve| date=2018-12-17}}</ref>{{citation needed|date=June 2018}}

[[Whitecourt crater]] in Alberta, Canada is estimated to be between 1,080 and 1,130 years old. The crater is approximately 36&nbsp;m (118&nbsp;ft) in diameter and 9&nbsp;m (30&nbsp;ft) deep, is heavily forested and was discovered in 2007 when a metal detector revealed fragments of meteoric iron scattered around the area.<ref>{{cite web |url=http://www.passc.net/EarthImpactDatabase/whitecourt.html |title=Whitecourt |access-date=2017-07-28 |archive-url=https://web.archive.org/web/20170718105534/http://www.passc.net/EarthImpactDatabase/whitecourt.html |archive-date=2017-07-18 |url-status=dead }}</ref><ref>{{cite web | url=http://www.whitecourtstar.com/2012/07/03/whitecourt-crater-attracts-visitors | archive-url=https://web.archive.org/web/20160305210537/http://www.whitecourtstar.com/2012/07/03/whitecourt-crater-attracts-visitors | url-status=dead | archive-date=2016-03-05 | title=Whitecourt Star }}</ref>

A Chinese record states that 10,000 people were killed in the 1490 [[Qingyang event]] with the deaths caused by a hail of "falling stones"; some astronomers hypothesize that this may describe an actual meteorite fall, although they find the number of deaths implausible.<ref>{{Citation | last1 = Yau | first1 = K. | last2 = Weissman | first2 = P. | last3 = Yeomans | first3 = D. | title = Meteorite Falls in China and Some Related Human Casualty Events | journal = Meteoritics | volume = 29 | issue = 6| pages = 864–871 | postscript = . | doi=10.1111/j.1945-5100.1994.tb01101.x | bibcode=1994Metic..29..864Y| year = 1994 }}</ref>

[[Kamil Crater]], discovered from [[Google Earth]] image review in [[Egypt]], {{convert|45|m|ft|abbr=on}} in diameter and {{convert|10|m|ft|abbr=on}} deep, is thought to have been formed less than 3,500 years ago in a then-unpopulated region of western Egypt. It was found February 19, 2009 by V. de Michelle on a Google Earth image of the East Uweinat Desert, Egypt.<ref>USGS Meteoritical Society, Bulletin database, Gebel Kamil Crater ... http://www.lpi.usra.edu/meteor/metbull.php?code=52031</ref>

====20th-century impacts====
[[File:Tunguska Ereignis-1.jpg|thumb|Trees knocked over by the [[Tunguska event|Tunguska blast]]]]

One of the best-known recorded impacts in modern times was the Tunguska event, which occurred in [[Siberia]], Russia, in 1908.<ref>{{cite web|title=Tunguska event {{!}} Summary, Cause, & Facts|url=https://www.britannica.com/event/Tunguska-event|access-date=2021-09-25|website=Encyclopedia Britannica|language=en}}</ref> This incident involved an explosion that was probably caused by the airburst of an asteroid or comet {{convert|5|to|10|km|mi|abbr=on}} above the Earth's surface, [[felling]] an estimated 80 million trees over {{convert|2150|km2|mi2|0|abbr=on}}.<ref>{{cite web|url=http://www.bbc.com/earth/story/20160706-in-siberia-in-1908-a-huge-explosion-came-out-of-nowhere|title=In Siberia in 1908, a huge explosion came out of nowhere|last=Hogenboom|first=Melissa|access-date=2017-03-30}}</ref>

In February 1947, another large bolide impacted the Earth in the [[Sikhote-Alin Mountains]], [[Primorsky Krai|Primorye]], Soviet Union. It was during daytime hours and was witnessed by many people, which allowed [[V. G. Fesenkov]], then chairman of the meteorite committee of the USSR Academy of Science, to estimate the meteoroid's orbit before it encountered the Earth. [[Sikhote-Alin meteorite|Sikhote-Alin]] is a massive fall with the overall size of the [[meteoroid]] estimated at {{convert|90000|kg|lb|abbr=on}}. A more recent estimate by Tsvetkov (and others) puts the mass at around {{convert|100000|kg|lb|abbr=on}}.<ref name="metmag">{{cite journal |url=http://meteoritemag.uark.edu/604.htm |journal=Meteorite Magazine | date=February 1996 |title=Sikhote-Alin Revisited |first=Roy |last=Gallant |volume=2 |page=8 |bibcode=1996Met.....2....8G |archive-url=https://web.archive.org/web/20100612144717/http://meteoritemag.uark.edu/604.htm |archive-date=2010-06-12 |url-status=dead }}</ref> It was an iron meteorite belonging to the chemical group IIAB and with a coarse octahedrite structure. More than 70 [[tonne]]s ([[metric ton]]s) of material survived the collision.

A case of a human injured by a space rock occurred on November 30, 1954, in [[Sylacauga, Alabama]].<ref>[http://imca.repetti.net/metinfo/metstruck.html Meteorite Hits Page] {{webarchive |url=https://web.archive.org/web/20090831183851/http://imca.repetti.net/metinfo/metstruck.html |date=August 31, 2009 }}</ref> There a {{convert|4|kg|lb|abbr=on}} stone chondrite crashed through a roof and hit Ann Hodges in her living room after it bounced off her radio. She was badly bruised by the [[Hodges Meteorite#Fragments|fragments]]. Several persons have since claimed to have been struck by "meteorites" but no verifiable meteorites have resulted.

A small number of [[meteorite fall]]s have been observed with automated cameras and recovered following calculation of the impact point. The first was the [[Příbram meteorite]], which fell in Czechoslovakia (now the Czech Republic) in 1959.<ref>{{Citation |last=Ceplecha |first=Z. |date=1961 |title=Multiple fall of Příbram meteorites photographed |journal=Bull. Astron. Inst. Czechoslovakia |volume=12 |pages=21–46 |bibcode=1961BAICz..12...21C }}</ref> In this case, two cameras used to photograph meteors captured images of the fireball. The images were used both to determine the location of the stones on the ground and, more significantly, to calculate for the first time an accurate orbit for a recovered meteorite.

Following the Příbram fall, other nations established automated observing programs aimed at studying infalling meteorites.<ref>Gritsevich, M.I. The Pribram, Lost City, Innisfree, and Neuschwanstein falls: An analysis of the atmospheric trajectories. Sol Syst Res 42, 372–390 (2008). https://doi.org/10.1134/S003809460805002X</ref> One of these was the [[Prairie Meteorite Network]], operated by the [[Smithsonian Astrophysical Observatory]] from 1963 to 1975 in the midwestern U.S. This program also observed a meteorite fall, the "Lost City" chondrite, allowing its recovery and a calculation of its orbit.<ref>{{Citation |last1=McCrosky |first1=R. E. |last2=Posen |first2=A. |last3=Schwartz |first3=G. |last4=Shao |first4=C. Y. |date=1971 |title=Lost City meteorite: Its recovery and a comparison with other fireballs |journal=J. Geophys. Res. |volume=76 |issue= 17|pages=4090–4108 |doi=10.1029/JB076i017p04090 |bibcode=1971JGR....76.4090M|hdl=2060/19710010847 |s2cid=140675097 |hdl-access=free }}</ref> Another program in Canada, the Meteorite Observation and Recovery Project, ran from 1971 to 1985. It too recovered a single meteorite, "Innisfree", in 1977.<ref>{{Citation |last1=Campbell-Brown |first1=M. D. |last2=Hildebrand |first2=A. |date=2005 |title=A new analysis of fireball data from the Meteorite Observation and Recovery Project (MORP) |journal=Earth, Moon, and Planets |volume=95 |issue=1–4 |pages=489–499 |doi=10.1007/s11038-005-0664-9 |bibcode = 2004EM&P...95..489C |s2cid=121255827 }}</ref> Finally, observations by the European Fireball Network, a descendant of the original Czech program that recovered Příbram, led to the discovery and orbit calculations for the [[Neuschwanstein]] meteorite in 2002.<ref>{{Citation |last1=Oberst |first1=J. |date=2004 |title=The multiple meteorite fall of Neuschwanstein: Circumstances of the event and meteorite search campaigns |journal=[[Meteoritics & Planetary Science]] |volume=39 |issue=10 |pages=1627–1641 |doi=10.1111/j.1945-5100.2004.tb00062.x |bibcode=2004M&PS...39.1627O |display-authors=2 |last2=Heinlein |first2=D. |last3=Spurný |first3=P.|doi-access=free }}</ref>

On August 10, 1972, a meteor which became known as the [[1972 Great Daylight Fireball]] was witnessed by many people as it moved north over the [[Rocky Mountains]] from the U.S. Southwest to Canada. It was filmed by a tourist at the [[Grand Teton National Park]] in [[Wyoming]] with an 8-millimeter color movie camera.<ref>{{YouTube|7M8LQ7_hWtE|Grand Teton Meteor Video}}</ref> In size range the object was roughly between a car and a house, and while it could have ended its life in a Hiroshima-sized blast, there was never any explosion. Analysis of the trajectory indicated that it never came much lower than {{convert|58|km|mi|0|abbr=on}} off the ground, and the conclusion was that it had grazed Earth's atmosphere for about 100 seconds, then skipped back out of the atmosphere and returned to its orbit around the Sun.

Many impact events occur without being observed by anyone on the ground. Between 1975 and 1992, American missile [[early warning satellite]]s picked up 136 major explosions in the upper atmosphere.<ref>{{Cite web|url=http://www.aerospaceweb.org/question/astronomy/q0296.shtml|title= Collisions with Near Earth Objects|website=www.aerospaceweb.org}}</ref> In the November 21, 2002, edition of the journal ''Nature'', Peter Brown of the University of Western Ontario reported on his study of U.S. early warning satellite records for the preceding eight years. He identified 300 flashes caused by {{convert|1|to|10|m|ft|0|abbr=on}} meteors in that time period and estimated the rate of Tunguska-sized events as once in 400 years.<ref>[https://archive.today/20120910052024/http://www.spaceref.com/news/viewpr.html?pid=9865 Satellite Study Establishes Frequency of Megaton-sized Asteroid Impacts] (SpaceRef November 20, 2002)</ref> [[Eugene Shoemaker]] estimated that an event of such magnitude occurs about once every 300 years, though more recent analyses have suggested he may have overestimated by an order of magnitude.

In the dark morning hours of January 18, 2000, a [[Tagish Lake (meteorite)|fireball]] exploded over the city of [[Whitehorse, Yukon Territory]] at an altitude of about {{convert|26|km|mi|0|abbr=on}}, lighting up the night like day. The meteor that produced the fireball was estimated to be about {{convert|4.6|m|ft|abbr=on}} in diameter, with a weight of 180 tonnes. This blast was also featured on the Science Channel series ''Killer Asteroids'', with several witness reports from residents in [[Atlin, British Columbia]].

==== 21st-century impacts ====
{{main|List of bolides}}
<!-- DDMMYYYY sequence Put 21st-c. discoveries of earlier earth impacts under appropriate heading  -->
On 7 June 2006, a meteor was observed striking a location in the [[Reisadalen]] valley in [[Nordreisa Municipality]] in [[Troms]] County, Norway. Although initial witness reports stated that the resultant fireball was equivalent to [[Atomic bombings of Hiroshima and Nagasaki|the Hiroshima nuclear explosion]], scientific analysis places the force of the blast at anywhere from 100 to 500 [[tonne#Use of mass as proxy for energy|tonnes]] TNT equivalent, around three percent of Hiroshima's yield.<ref>[https://archive.today/20120629002618/http://skyandtelescope.com/news/article_1742_1.asp Norway Impact Gentler Than Atomic Bomb] (Sky & Telescope June 16, 2006)</ref>

On 15 September 2007, a chondritic [[Carancas impact event|meteor crashed near the village of Carancas]] in southeastern Peru near [[Lake Titicaca]], leaving a water-filled hole and spewing gases across the surrounding area. Many residents became ill, apparently from the noxious gases shortly after the impact.

On 7 October 2008, an approximately 4 meter asteroid labeled {{mpl|2008 TC|3}} was tracked for 20 hours as it approached Earth and as it fell through the atmosphere and impacted in Sudan. This was the first time an object was detected before it reached the atmosphere and hundreds of pieces of the meteorite were recovered from the [[Nubian Desert]].<ref>[https://www.wired.com/wiredscience/2009/03/meteorite/ First-Ever Asteroid Tracked From Space to Earth], Wired, March 25, 2009 {{webarchive |url=https://web.archive.org/web/20140321060157/http://www.wired.com/wiredscience/2009/03/meteorite/ |date=March 21, 2014 }}</ref>

[[File:Chelyabinsk meteor trace 15-02-2013.jpg|thumb|Trail left by the exploding Chelyabinsk meteor as it passed over the city.]]

On 15 February 2013, an asteroid entered Earth's atmosphere over [[Russia]] as a [[Bolide|fireball]] and exploded above the city of [[Chelyabinsk]] during its passage through the [[Ural (region)|Ural Mountains region]] at 09:13 [[Yekaterinburg Time|YEKT]] (03:13 [[Coordinated Universal Time|UTC]]).<ref name=meteor>{{cite web|title=Russian Meteor|url=http://www.nasa.gov/topics/solarsystem/features/russianmeteor.html|publisher=NASA|access-date=15 February 2013|archive-date=18 February 2013|archive-url=https://web.archive.org/web/20130218034325/http://www.nasa.gov/topics/solarsystem/features/russianmeteor.html|url-status=dead}}</ref><ref>{{cite news|url=https://www.usatoday.com/story/news/world/2013/02/15/russia-meteorite/1921991/ |title=Meteor in central Russia injures at least 500 |work=[[USA Today]] |access-date=15 February 2013 |first1=Anna |last1=Arutunyan |first2=Marc |last2=Bennetts |date=15 February 2013}}</ref> The object's air burst occurred at an altitude between {{convert|30|and|50|km|mi|abbr=on}} above the ground,<ref>{{cite news |title=Meteor falls in Russia, 700 injured by blasts |url=http://bigstory.ap.org/article/meteorite-falls-russian-urals |agency=Associated Press |access-date=15 February 2013 |archive-date=18 February 2013 |archive-url=https://web.archive.org/web/20130218034039/http://bigstory.ap.org/article/meteorite-falls-russian-urals |url-status=dead }}</ref> and about 1,500 people were injured, mainly by broken window glass shattered by the shock wave. Two were reported in serious condition; however, there were no fatalities.<ref name="chelyabinsk">{{cite web |url=http://www.vesti.ru/doc.html?id=1033922|script-title=ru:Метеоритный дождь над Уралом: пострадали 1200 человек |language= ru |work= Vesti |date=15 February 2013|access-date=15 February 2013 | location = [[Russia|RU]]}}</ref> Initially some 3,000 buildings in six cities across the region were reported damaged due to the explosion's shock wave, a figure which rose to over 7,200 in the following weeks.<ref>{{cite news|last=Marson|first=James|title=Meteorite Hits Russia, Causing Panic|url=https://www.wsj.com/articles/SB10001424127887324162304578305163574597722?mod=WSJ_hpp_LEFTTopStories|newspaper=Wall Street Journal|access-date=15 February 2013|author2=Gautam Naik}}</ref><ref>{{cite magazine|last=Ewait|first=David|title=Exploding Meteorite Injures A Thousand People In Russia|url=https://www.forbes.com/sites/davidewalt/2013/02/15/exploding-meteorite-injures-a-thousand-people-in-russia/|magazine=Forbes|access-date=15 February 2013}}</ref> The Chelyabinsk meteor was estimated to have caused over $30 million in damage.<ref>{{cite news|url=http://in.reuters.com/article/russia-meteorite-idINDEE91E03320130215|title=Meteorite explodes over Russia, more than 1,000 injured|author=Andrey Kuzmin|work=Reuters|date=16 February 2013|access-date=16 February 2013|archive-date=6 March 2016|archive-url=https://web.archive.org/web/20160306214917/http://in.reuters.com/article/russia-meteorite-idINDEE91E03320130215|url-status=dead}}</ref><ref name="RBTH-23513">{{cite news | url=http://rbth.ru/news/2013/03/05/meteorite-caused_emergency_situation_regime_over_in_chelyabinsk_region_23513.html | title=Meteorite-caused emergency situation regime over in Chelyabinsk region | work=Russia Beyond The Headlines | publisher=Rossiyskaya Gazeta | date=5 March 2013 | agency=[[Interfax]] | access-date=6 March 2013 | archive-date=23 June 2013 | archive-url=https://archive.today/20130623230931/http://rbth.ru/news/2013/03/05/meteorite-caused_emergency_situation_regime_over_in_chelyabinsk_region_23513.html | url-status=dead }}</ref> It is the largest recorded object to have encountered the Earth since the 1908 Tunguska event.<ref>{{cite news|url=https://www.economist.com/blogs/babbage/2013/02/asteroid-impacts?fsrc=nlw%7Cnewe%7C2-15-2013%7C5019506%7C37104620%7C|title=Asteroid impacts – How to avert Armageddon
 |newspaper=[[The Economist]] |date=15 February 2013|access-date=16 February 2013}}</ref><ref>{{cite news|url=https://www.nytimes.com/2013/02/16/science/space/size-of-blast-and-number-of-injuries-are-seen-as-rare-for-a-rock-from-space.html?ref=science&_r=0|title=Size of Blast and Number of Injuries Are Seen as Rare for a Rock From Space|author=Kenneth Chang|work=[[The New York Times]]|date=15 February 2013|access-date=16 February 2013}}</ref> The meteor is estimated to have an initial diameter of 17–20 metres and a mass of roughly 10,000 tonnes. On 16 October 2013, a team from Ural Federal University led by Victor Grokhovsky recovered a large fragment of the meteor from the bottom of Russia's Lake Chebarkul, about 80&nbsp;km west of the city.<ref>{{cite magazine|last=Beatty|first=J. Kelly|title=Russian Fireball Fragment Found|magazine=Australian Sky & Telescope|date=February–March 2014|page=12|issn=1832-0457}}</ref>

On 1 January 2014, a 3-meter (10 foot) asteroid, [[2014 AA]] was discovered by the [[Mount Lemmon Survey]] and observed over the next hour, and was soon found to be on a collision course with Earth. The exact location was uncertain, constrained to a line between [[Panama]], the central Atlantic Ocean, [[The Gambia]], and Ethiopia. Around roughly the time expected (2 January 3:06 UTC) an infrasound burst was detected near the center of the impact range, in the middle of the Atlantic Ocean.<ref name="Farnocchia2016">{{cite journal|title=The trajectory and atmospheric impact of asteroid 2014 AA|first1=Davide|last1=Farnocchia|first2=Steven R.|last2=Chesley|first3=Peter G.|last3=Brown|first4=Paul W.|last4=Chodas|date=1 August 2016|journal=[[Icarus (journal)|Icarus]]|volume=274|pages=327–333|bibcode=2016Icar..274..327F|doi=10.1016/j.icarus.2016.02.056 }}</ref><ref name="Marcos2016">{{cite journal|title=Homing in for New Year: impact parameters and pre-impact orbital evolution of meteoroid 2014 AA|first1=C.|last1=de la Fuente Marcos|first2=R.|last2=de la Fuente Marcos|first3=P.|last3=Mialle|date=13 October 2016|journal=[[Astrophysics and Space Science]]|volume=361|issue=11|pages=358 (33 pp.)|arxiv=1610.01055|bibcode=2016Ap&SS.361..358D |doi=10.1007/s10509-016-2945-3|s2cid=119251345}}</ref> This marks the second time a natural object was identified prior to impacting earth after 2008 TC3.

Nearly two years later, on October 3, [[WT1190F]] was detected orbiting Earth on a highly eccentric orbit, taking it from well within the [[Geocentric orbit|Geocentric satellite ring]] to nearly twice the orbit of the Moon. It was estimated to be perturbed by the Moon onto a collision course with Earth on November 13. With over a month of observations, as well as precovery observations found dating back to 2009, it was found to be far less dense than a natural asteroid should be, suggesting that it was most likely an unidentified artificial satellite. As predicted, it fell over [[Sri Lanka]] at 6:18 UTC (11:48 local time). The sky in the region was very overcast, so only an airborne observation team was able to successfully observe it falling above the clouds. It is now thought to be a remnant of the [[Lunar Prospector]] mission in 1998, and is the third time any previously unknown object – natural or artificial – was identified prior to impact.

On 22 January 2018, an object, [[A106fgF]], was discovered by the [[Asteroid Terrestrial-impact Last Alert System]] (ATLAS) and identified as having a small chance of impacting Earth later that day.<ref>[https://groups.yahoo.com/neo/groups/mpml/conversations/messages/33680 Bill Gray MPML]{{dead link|date=December 2023|bot=medic}}{{cbignore|bot=medic}}</ref> As it was very dim, and only identified hours before its approach, no more than the initial 4 observations covering a 39-minute period were made of the object. It is unknown if it impacted Earth or not, but no fireball was detected in either infrared or infrasound, so if it did, it would have been very small, and likely near the eastern end of its potential impact area – in the western Pacific Ocean.

On 2 June 2018, the [[Mount Lemmon Survey]] detected {{mpl|2018 LA}} (ZLAF9B2), a small 2–5 meter asteroid which further observations soon found had an 85% chance of impacting Earth. Soon after the impact, a fireball report from [[Botswana]] arrived to the [[American Meteor Society]]. Further observations with ATLAS extended the observation arc from 1 hour to 4 hours and confirmed that the asteroid orbit indeed impacted Earth in southern Africa, fully closing the loop with the fireball report and making this the third natural object confirmed to impact Earth, and the second on land after {{mp|2008 TC|3}}.<ref name="orientation">{{cite journal
|last1=de la Fuente Marcos |first1=Carlos
|last2=de la Fuente Marcos |first2=Raúl
|date=18 June 2018
|title=On the Pre-impact Orbital Evolution of 2018 LA, Parent Body of the Bright Fireball Observed Over Botswana on 2018 June 2
|journal=[[Research Notes of the AAS]]
|volume=2
|issue=2
|page=57
|arxiv=1806.05164
|bibcode=2018RNAAS...2...57D
|doi=10.3847/2515-5172/aacc71|s2cid=119325928
|doi-access=free
}}</ref><ref name="pre-impact2">{{cite journal
|last1=de la Fuente Marcos |first1=Carlos
|last2=de la Fuente Marcos |first2=Raúl
|date=26 July 2018
|title=Pre-airburst Orbital Evolution of Earth's Impactor 2018 LA: An Update
|journal=[[Research Notes of the AAS]]
|volume=2
|issue=3
|page=131
|arxiv=1807.08322
|bibcode=2018RNAAS...2..131D
|doi=10.3847/2515-5172/aad551|s2cid=119208392
|doi-access=free
}}</ref><ref name="excess">{{cite journal |last1=de la Fuente Marcos |first1=C. |last2=de la Fuente Marcos | first2= R.|title=Waiting to make an impact: A probable excess of near-Earth asteroids in 2018 LA-like orbits |journal=[[Astronomy and Astrophysics]] |volume= 621|pages= A137|date=2019 |doi=10.1051/0004-6361/201834313
 |arxiv=1811.11845 |bibcode=2019A&A...621A.137D|s2cid=119538516 }}</ref>

On 8 March 2019, [[NASA]] announced the detection of a large airburst that occurred on 18 December 2018 at 11:48 local time off the eastern coast of the [[Kamchatka Peninsula]]. The [[Kamchatka superbolide]] is estimated to have had a mass of roughly 1600 tons, and a diameter of 9 to 14 meters depending on its density, making it the third largest asteroid to impact Earth since 1900, after the Chelyabinsk meteor and the Tunguska event. The fireball exploded in an airburst {{convert|25.6|km|mi}} above Earth's surface.

[[2019 MO]], an approximately 4m asteroid, was detected by [[Asteroid Terrestrial-impact Last Alert System|ATLAS]] a few hours before it impacted the Caribbean Sea near Puerto Rico in June 2019.<ref>{{Cite web |date=25 June 2019 |title=Breakthrough: UH team successfully locates incoming asteroid |url=https://legacy.ifa.hawaii.edu/info/press-releases/ATLAS_2019MO/ |access-date=12 March 2023 |website=Institute for Astronomy – University of Hawaii}}</ref>

In 2023, a small meteorite is believed to have crashed through the roof of a home in Trenton, New Jersey. The metallic rock was approximately 4 inches by 6 inches and weighed 4 pounds. The item was seized by police and tested for radioactivity.<ref>{{Cite web |url=https://apnews.com/article/meteorite-hits-home-hopewell-new-jersey-fd8391f8c5daea1e596ed85ed3ae5a68 |title=Possible meteorite crashes into New Jersey home, no injuries |date=May 9, 2023 |publisher=[[AP News]] |access-date=May 10, 2023}}</ref> The object was later confirmed to be a meteorite by scientists at The College of New Jersey, as well as meteorite expert Jerry Delaney, who previously worked at Rutgers University and the American Museum of Natural History.<ref>{{Cite web |url=https://apnews.com/article/meteorite-hits-home-hopewell-new-jersey-91fecf2eb7e5ffb938bfb68920dc6011 |title=Experts: Metallic object that crashed into New Jersey home was a meteorite |date=May 11, 2023 |publisher=[[AP News]] |access-date=May 14, 2023}}</ref>

===== Asteroid impact prediction =====
{{main|Asteroid impact prediction}}

[[File:2018 LA-orbit.png|thumb|250px|[[Orbit]] and positions of [[2018 LA]] and Earth, 30 days before impact. The diagram illustrates how orbit data can be used to predict impacts well in advance. Note that in this particular instance the asteroid's orbit was not known until a few hours before impact. The diagram was constructed afterwards for illustration.]]

In the late 20th and early 21st century scientists put in place measures to detect [[Near Earth object]]s, and predict the dates and times of [[asteroids]] impacting Earth, along with the locations at which they will impact. The [[International Astronomical Union]] [[Minor Planet Center]] (MPC) is the global clearing house for information on asteroid orbits. [[NASA]]'s [[Sentry (monitoring system)|Sentry System]] continually scans the MPC catalog of known asteroids, analyzing their orbits for any possible future impacts.<ref>{{YouTube|id=53Js-_vo3mo|title=How Does NASA Spot a Near-Earth Asteroid?}}</ref> Currently none are predicted (the single highest probability impact currently listed is ~7 m asteroid {{mpl|2010 RF|12}}, which is due to pass earth in September 2095 with only a 5% predicted chance of impacting).<ref>{{cite web|title=Sentry: Earth Impact Monitoring|url=https://cneos.jpl.nasa.gov/sentry/|website=Jet Propulsion Laboratory|publisher=NASA|access-date=25 August 2018}}</ref>

Currently prediction is mainly based on cataloging [[asteroids]] years before they are due to impact. This works well for larger asteroids (> 1 [[kilometre|km]] across) as they are easily seen from a long distance. Over 95% of them are already known and their [[orbit]]s have been measured, so any future impacts can be predicted long before they are on their final approach to Earth. Smaller objects are too faint to observe except when they come very close and so most cannot be observed before their final approach. Current mechanisms for detecting asteroids on final approach rely on wide-field ground based [[telescopes]], such as the ATLAS system. However, current telescopes only cover part of the Earth and even more importantly cannot detect asteroids on the day-side of the planet, which is why so few of the smaller asteroids that commonly impact Earth are detected during the few hours that they would be visible.<ref name="JPL-2017-SDT-Update">{{cite news
  |title      = Update to Determine the Feasibility of Enhancing the Search and Characterization of NEOs
  |work       = Near-Earth Object Science Definition Team Report 2017
  |publisher  = NASA
  |url        = https://www.nasa.gov/sites/default/files/atoms/files/2017_neo_sdt_final_e-version.pdf
  |access-date = 7 July 2018}}</ref>
So far only four impact events have been successfully predicted, all from innocuous 2–5 m diameter asteroids and detected a few hours in advance.

{{wide image|SmallAsteroidImpacts-Frequency-Bolide-20141114.jpg|500px|align-cap=center|Ground based telescopes can only detect objects approaching on the night-side of the planet, away from the [[Sun]]. Roughly half of impacts occur on the day-side of the planet.}}

===Current response status===
{{main|Asteroid impact avoidance}}
In April 2018, the [[B612 Foundation]] reported "It's 100 per cent certain we’ll be hit [by a devastating asteroid], but we're not 100 per cent certain when."<ref name="INQ-20180428"/> Also in 2018, [[physicist]] [[Stephen Hawking]], in his final book ''[[Brief Answers to the Big Questions (book)|Brief Answers to the Big Questions]]'', considered an asteroid collision to be the biggest threat to the planet.<ref name="WP-20181015"/><ref name="QZ-20181014"/> In June 2018, the US National Science and Technology Council warned that America is unprepared for an [[Asteroid impact avoidance|asteroid impact event]], and has developed and released the ''"[https://trumpwhitehouse.archives.gov/wp-content/uploads/2018/06/National-Near-Earth-Object-Preparedness-Strategy-and-Action-Plan-23-pages-1MB.pdf National Near-Earth Object Preparedness Strategy Action Plan]"'' to better prepare.<ref name="WH-20180621"/><ref name="GIZ-20180621"/><ref name="ICARUS-220180522"/><ref name="NYT-20180614"/><ref name="NYT-20180614c"/> According to expert testimony in the United States Congress in 2013, [[NASA]] would require at least five years of preparation to launch a mission to intercept an asteroid.<ref name="US-Congress-20130410" />  The preferred method is to deflect rather than disrupt an asteroid.<ref name="PHYS-20190304">{{cite news |author=Johns Hopkins University
 |title=Asteroids are stronger, harder to destroy than previously thought
 |url=https://phys.org/news/2019-03-asteroids-stronger-harder-previously-thought.html
 |date=4 March 2019 |work=[[Phys.org]] |access-date=4 March 2019 |author-link=Johns Hopkins University
}}</ref><ref name="ICRS-20190315">{{cite journal |last1=El Mir |first1=Charles |last2=Ramesh |first2=KT |last3=Richardson |first3=Derek C.
 |title=A new hybrid framework for simulating hypervelocity asteroid impacts and gravitational reaccumulation
 |date=15 March 2019 |journal=[[Icarus (journal)|Icarus]] |volume=321 |pages=1013–1025
 |doi= 10.1016/j.icarus.2018.12.032|bibcode=2019Icar..321.1013E|s2cid=127119234 }}</ref><ref name="NYT-20190308">{{cite news |last=Andrews |first=Robin George
 |title=If We Blow Up an Asteroid, It Might Put Itself Back Together – Despite what Hollywood tells us, stopping an asteroid from creating an extinction-level event by blowing it up may not work.
 |url=https://www.nytimes.com/2019/03/08/science/asteroids-nuclear-weapons.html
 |date=8 March 2019 |work=[[The New York Times]] |access-date=9 March 2019}}</ref>