Editing Near-Earth object (section)

==== Impacts ====
{{main|Impact event}}
{{see also|List of predicted asteroid impacts on Earth|List of bolides}}

When a near-Earth object impacts Earth, objects up to a few tens of metres across ordinarily explode in the [[Mesosphere|upper atmosphere]] (most of them harmlessly), with most or all of the solids [[Evaporation|vaporized]] and only small amounts of meteorites arriving to the Earth surface. Larger objects, by contrast, hit the water surface, forming [[tsunami]] waves, or the solid surface, forming [[impact crater]]s.<ref>{{Cite journal |last1=Chapman |first1= Clark R. |last2=Morrison |first2= David |name-list-style=amp |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|s2cid=4305299 |url=https://zenodo.org/records/1233151/files/article.pdf |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20240702165419/https://zenodo.org/records/1233151/files/article.pdf |archive-date=July 2, 2024}}</ref>

The frequency of impacts of objects of various sizes is estimated on the basis of orbit simulations of NEO populations, the frequency of impact craters on the Earth and the Moon, and the frequency of close encounters.<ref name="Collins2005">{{cite journal |last1=Collins |first1=Gareth S. |last2=Melosh |first2=H. Jay |last3=Marcus |first3=Robert A. |title=Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth |journal=[[Meteoritics & Planetary Science]] |volume=40 |number=6 |pages=817–840 |date=June 2005 |doi=10.1111/j.1945-5100.2005.tb00157.x |url=https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/effects.pdf |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20241217213340/https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/effects.pdf |archive-date=December 17, 2024 |bibcode=2005M&PS...40..817C |hdl=10044/1/11554 |s2cid=13891988 |hdl-access=free}}</ref><ref name="Asher2005">{{cite journal |last1=Asher |first1=D. J. |last2=Bailey |first2=M. |last3=Emel'Yanenko |first3=V. |last4=Napier |first4=W. |title=Earth in the Cosmic Shooting Gallery |journal=[[The Observatory (journal)|The Observatory]] |volume=125 |issue=2 |pages=319–322 |date=October 2005 |bibcode=2005Obs...125..319A}}</ref> The study of impact craters indicates that impact frequency has been more or less steady for the past 3.5&nbsp;billion years, which requires a steady replenishment of the NEO population from the [[asteroid main belt]].<ref name="MorbidelliAstIII"/> One impact model based on widely accepted NEO population models estimates the average time between the impact of two stony asteroids with a diameter of at least {{convert|4|m|ft|abbr=on}} at about one year; for asteroids {{convert|7|m|ft|abbr=on}} across (which impacts with as much energy as the atomic bomb dropped on [[Atomic bombings of Hiroshima and Nagasaki|Hiroshima]], approximately 15 kilotonnes of TNT) at five years, for asteroids {{convert|60|m|ft|abbr=on}} across (an impact energy of 10 [[megatons]], comparable to the [[Tunguska event]] in 1908) at 1,300 years, for asteroids {{convert|1|km|mi|abbr=on}} across at 440 thousand years, and for asteroids {{convert|5|km|mi|abbr=on}} across at 18 million years.<ref name="Earth-impact"/> Some other models estimate similar impact frequencies,<ref name="MorbidelliAstIII"/> while others calculate higher frequencies.<ref name="Asher2005"/> For Tunguska-sized (10 megaton) impacts, the estimates range from one event every 2,000–3,000 years to one event every 300 years.<ref name="Asher2005"/>

{{wide image|SmallAsteroidImpacts-Frequency-Bolide-20141114.jpg|600px|align-cap=center|Location and impact energy of small asteroids impacting Earth's atmosphere}}

The second-largest observed event after the Tunguska meteor was a 1.1 megaton air blast in 1963 near the [[Prince Edward Islands]] between South Africa and Antarctica. However, this event was detected only by [[infrasound]] sensors,<ref name="David_spacecom"/><ref name=silber>{{cite journal |first1=Elizabeth A. |last1=Silber |first2=Douglas O. |last2=Revelle |first3=Peter G. |last3=Brown |first4=Wayne N. |last4=Edwards |title=An estimate of the terrestrial influx of large meteoroids from infrasonic measurements |journal=[[Journal of Geophysical Research]] |volume=114 |issue=E8 |year=2009 |doi=10.1029/2009JE003334 |doi-access=free |bibcode=2009JGRE..114.8006S}}</ref> which led to speculation that this may have been a [[nuclear test]].<ref name=Allen>{{cite journal |last1=Allen |first1=Robert S. |title=Antarctic Explosion Could Have Been Nuclear Detonation |journal=[[The San Bernardino Sun]] |issue=4 December |year=1963 |at=p. 40 col. f |url=https://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=SBS19631204.1.40&e=-------en--20--1--txt-txIN--------1}}</ref> The third-largest, but by far best-observed impact, was the [[Chelyabinsk meteor]] of 15 February 2013. A previously unknown {{convert|20|m|ft|abbr=on}} asteroid exploded above this Russian city with an equivalent blast yield of 400–500 kilotons.<ref name="David_spacecom">{{cite news |first=Leonard |last=David |title=Russian fireball explosion shows meteor risk greater than thought |date=November 1, 2013 |work=Space.com |url=http://www.space.com/23423-russian-fireball-meteor-airburst-risk.html |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20170819031019/https://www.space.com/23423-russian-fireball-meteor-airburst-risk.html |archive-date=August 19, 2017}}</ref> The calculated orbit of the pre-impact asteroid is similar to that of Apollo asteroid {{mpl|2011 EO|40}}, making the latter the meteor's possible parent body.<ref>{{cite journal |title=Reconstructing the Chelyabinsk event: Pre-impact orbital evolution |first1=C. |last1=de&nbsp;la&nbsp;Fuente Marcos |first2=R. |last2=de&nbsp;la&nbsp;Fuente Marcos |date=September 1, 2014 |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=443 |issue=1 |pages=L39–L43 |arxiv=1405.7202 |bibcode=2014MNRAS.443L..39D |doi=10.1093/mnrasl/slu078 |doi-access=free |s2cid=118417667}}</ref>

[[File:Sar2667 as it entered Earth's atmosphere over the north of France.jpg|thumb|Seven hours after discovery, {{mpl|2023 CX|1}} burns up as a meteor over northern France]]
On October 7, 2008, 20 hours after it was first observed and 11 hours after its trajectory has been calculated and announced, {{convert|4|m|ft|abbr=on}} asteroid {{mpl|2008 TC|3}} blew up {{convert|37|km|sigfig=2|abbr=on}} above the [[Nubian Desert]] in Sudan. It was the first time that an asteroid was observed and its impact was predicted prior to its entry into the atmosphere as a [[meteor]]. 10.7&nbsp;kg of meteorites were recovered after the impact.<ref>{{cite journal |last1=Shaddad |first1=Muawia H. |display-authors=etal |title=The recovery of asteroid {{mp|2008 TC|3}} |journal=Meteoritics & Planetary Science |volume=45 |issue=10–11 |pages=1557–1589 |date=October 2010 |doi=10.1111/j.1945-5100.2010.01116.x |bibcode=2010M&PS...45.1557S |doi-access=free}}</ref> {{As of|2024|12}}, eleven impacts have been predicted, all of them small bodies that produced meteor explosions,<ref>{{Cite news |first=Brett |last=Tingley |title=Tiny asteroid detected hours before hitting Earth to become 4th 'imminent impactor' of 2024 |date=December 3, 2024 |work=Space.com |url=https://www.space.com/the-universe/asteroids/tiny-asteroid-detected-hours-before-hitting-earth-to-become-4th-imminent-impactor-of-2024 |access-date=December 31, 2024 |url-status=live |archive-url=https://web.archive.org/web/20241220093823/https://www.space.com/the-universe/asteroids/tiny-asteroid-detected-hours-before-hitting-earth-to-become-4th-imminent-impactor-of-2024 |archive-date=December 20, 2024}}</ref> with some impacts in remote areas only detected by the [[Comprehensive Nuclear-Test-Ban Treaty Organization]]'s [[Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization#International Monitoring System (IMS)|International Monitoring System (IMS)]], a network of infrasound sensors designed to detect the detonation of nuclear devices.<ref name="S&T140102">{{cite news |first1=Kelly |last1=Beatty |title=Small asteroid 2014&nbsp;AA hits Earth |magazine=[[Sky & Telescope]] |date=January 2, 2014 |url=http://www.skyandtelescope.com/astronomy-news/small-asteroid-2014-aa-hitsearth/ |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20240725072341/https://skyandtelescope.org/astronomy-news/small-asteroid-2014-aa-hitsearth/ |archive-date=July 25, 2024}}</ref> [[Asteroid impact prediction]] remains in its infancy and successfully predicted asteroid impacts are rare. The vast majority of impacts recorded by IMS are not predicted.<ref>{{cite web |title=Fireballs. Fireball and Bolide Data |date=December 20, 2024 |publisher=NASA/JPL |url=http://cneos.jpl.nasa.gov/fireballs/ |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20250101175038/http://cneos.jpl.nasa.gov/fireballs/ |archive-date=January 1, 2025}}</ref>

Observed impacts aren't restricted to the surface and atmosphere of Earth. Dust-sized NEOs have impacted man-made spacecraft, including the space probe [[Long Duration Exposure Facility]], which collected [[interplanetary dust cloud|interplanetary dust]] in low Earth orbit for six years from 1984.<ref name="Rubin2010"/> Impacts on the Moon can be observed as flashes of light with a typical duration of a fraction of a second.<ref name="NASA-lunar-impacts"/> The first lunar impacts were recorded during the 1999 Leonid storm.<ref>{{cite encyclopedia |last1=Rubio |first1=Luis R. Bellot |last2=Ortiz |first2=Jose L. |last3=Sada |first3=Pedro V. |title=Observation and Interpretation of Meteoroid Impact Flashes on the Moon |editor1-last=Jenniskens |editor1-first=P. |editor2-last=Rietmeijer |editor2-first=F. |editor3-last=Brosch |editor3-first=N. |editor4-last=Fonda |editor4-first=M. |display-editors=1 |encyclopedia=Leonid Storm Research |publisher=Springer |location=Dordrecht |year=2000 |pages=575–598 |isbn=978-90-481-5624-5 |doi=10.1007/978-94-017-2071-7_42 |bibcode=2000lsr..book..575B |s2cid=118392496}}</ref> Subsequently, several continuous monitoring programs were launched.<ref name="NASA-lunar-impacts">{{cite web |title=Lunar Impact Monitoring Program |publisher=NASA |url=https://www.nasa.gov/meteoroid-environment-office/about-lunar-impact-monitoring/ |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20240127144250/https://www.nasa.gov/meteoroid-environment-office/about-lunar-impact-monitoring/ |archive-date=January 27, 2024}}</ref><ref name="2013-lunar-impact"/><ref name="ESA-lunar-impacts">{{cite web |title=About the NELIOTA project |publisher=ESA |url=https://neliota.astro.noa.gr/About/Project |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20240307162344/https://neliota.astro.noa.gr/About/Project?AspxAutoDetectCookieSupport=1 |archive-date=March 7, 2024}}</ref> A lunar impact that was observed on September 11, 2013, lasted 8 seconds, was likely caused by an object {{convert|0.6–1.4|m|ft|abbr=on}} in diameter,<ref name="2013-lunar-impact">{{cite news |first=Michele |last=Catanzaro |title=Largest lunar impact caught by astronomers |date=February 24, 2014 |journal=Nature |url=https://www.nature.com/articles/nature.2014.14773 |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20211004133116/https://www.nature.com/articles/nature.2014.14773 |archive-date=October 4, 2021}}</ref> and created a new crater {{convert|40|m|ft|abbr=on}} across, was the largest ever observed {{as of|lc=y|2019|07}}.<ref>{{cite web |title=MIDAS: Moon Impacts Detection and Analysis System. Main Results |work=Meteoroides.NET |url=http://www.meteoroides.net/e_midas_results.html |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20240307162029/http://www.meteoroides.net/e_midas_results.html |archive-date=March 7, 2024}}</ref>