The most powerful meteor air burst in the modern era was the 1908 Tunguska event. During this event a stony meteoroid about 50–60 m (160–200 ft) in size[1][2]: p. 178 exploded at an altitude of 5–10 km (16,000–33,000 ft) over a sparsely populated forest in Siberia. The resulting shock wave flattened an estimated 80 million trees over a 2,150 km2 (830 sq mi) area, and may have killed 3 people.[1][3][4][5][6]
Meteoroids enter the Earth's atmosphere from outer space traveling at speeds of at least 11 km/s (7 mi/s) and often much faster. Despite moving through the rarified upper reaches of Earth's atmosphere the immense speed at which a meteor travels rapidly compresses the air in its path. The meteoroid then experiences what is known as ram pressure. As the air in front of the meteoroid is compressed its temperature quickly rises. This is not due to friction, rather it is an adiabatic process, a consequence of many molecules and atoms being forced to occupy a smaller space. Ram pressure and the very high temperatures it causes are the reasons few meteors make it all the way to the ground. Most simply burn up or are ablated into tiny fragments. Larger or more solid meteorites may explode instead.
Airburst explosions
The use of the term explosion is somewhat loose in this context, and can be confusing. This confusion is exacerbated by the tendency for airburst energies to be expressed in terms of nuclear weapon yields, as when the Tunguska airburst is given a rating in megatons of TNT. Large meteoroids do not explode in the sense of chemical or nuclear explosives. Rather, at a critical moment in its atmospheric entry the enormous ram pressure experienced by the leading face of the meteoroid converts the body's immense momentum into a force blowing it apart over a nearly instantaneous span of time.[7] That is, the mass of the meteoroid suddenly ceases to move at orbital speeds when it breaks up. Conservation of energy implies much of this orbital velocity is converted into heat.
In essence, the meteoroid is ripped apart by its own speed. This occurs when fine tendrils of superheated air force their way into cracks and faults in the leading face's surface. Once this high pressure plasma gains entry to the meteoroid's interior it exerts tremendous force on the body's internal structure. This occurs because the superheated air now exerts its force over a much larger surface area, as when the wind suddenly fills a sail. This sudden rise in the force exerted on the meteoroid overwhelms the body's structural integrity and it begins to break up. The breakup of the meteoroid yields an even larger total surface area for the superheated air to act upon and a cycle of amplification rapidly occurs. This is the explosion, and it causes the meteoroid to disintegrate with hypersonic velocity, a speed comparable to that of explosive detonation.[7]
Frequency
The table from Earth Impact Effects Program (EIEP) estimates the average frequency of airbursts and their energy yield in kilotons (kt) or megatons (Mt) of TNT equivalent.
Based on density of 2600 kg/m3, speed of 17 km/s, and an impact angle of 45°
Events
Before the 20th century
While airbursts undoubtedly happened prior to the 20th century, reliable reports of such are sparse. A possible example is the Qingyang event of 1490, which had an unknown energy yield but was reportedly powerful enough to cause 10,000 deaths.[10] Modern researchers are sceptical about the figure, but had the Tunguska event occurred over a highly populous district, it might have caused a similar level of destruction.[10] There has also been unofficial speculations that the mysterious 1626 Wanggongchang Explosion in the Ming dynasty capital Beijing, which reportedly killed 20,000 people and was long blamed onto potential mishandling of black gunpowder stored at the local armoury, might actually be a Tunguska-like impact event/air burst that coincidentally happened over a gunpowder factory.[citation needed]
A study published in 2020 claimed that on 22 August 1888, a meteorite killed a man and left another paralyzed in Sulaymaniyah, Iraq, as reported by the local governor to Sultan Abdul Hamid II of the Ottoman Empire.[11]
After 1901
Depending on the estimate, there were only 3–4 known airbursts in the years 1901–2000 with energy yield greater than 80 kilotons (in 1908, 1930?, 1932?, and 1963), roughly consistent with the estimate of the EIEP table. However, the 1963 event may have not been a meteor, but instead a nuclear test. Most values for the 1930 Curuçá River event put it well below 1 megaton, comparable to the Chelyabinsk meteor and Kamchatka superbolide.[12][13][14] The Comprehensive Nuclear-Test-Ban Treaty Organization and modern technology has improved multiple detection of airbursts with energy yield 1–2 kilotons every year within the last decade.[15]
The first airburst of the 21st century with yield greater than 100 kilotons came from the 2013 Chelyabinsk meteor, which had an estimated diameter of 20 metres.
Known as the 1919 Michigan Event. A gigantic meteor was seen approaching from the east. A brilliant flash of light, thunder, and an earthquake lasting three minutes were reported. Damage to property over a large area as well as to telegraph, telephone and electrical systems.[17]
Also known as the 1930 Curuçá River event or "Brazilian Tunguska".[19] Hypothesised to be generated by three meteor fragments. An astrobleme of 1 km was found on the ground, but may be related to an older feature.[19][20][21][22][23]
An exceptionally large meteor fall woke witnesses with a terrific roar, concussion and brilliant illumination. Shortly after a region of devastated forest perhaps ten miles by five was located, where trees large and small had been pushed over. The view must have been obtained from the top of Maumauktpautau. Other reports say that trees had been broken or twisted off 25 ft above their bases. An elongated damaged area more than 20 miles in extent was reported seen from an aircraft.[25] A 1937 report says a 30-mile Path Cut By Meteor in Jungle and that the meteor fell, some ten miles from a place named Camshock.[26] The only place near there was Davidson's cottage high on the side of Marudi Mountain.
ru:Катавский болид (Katavsky bolide). Residents saw a fireball flying at a high speed in the dark sky, followed by roaring like the sound of a speeding steam locomotive. Fragments were left as a result of the event.[citation needed]
Sikhote-Alin bolide. The largest meteorite fall of recent times with total mass of fragments at 23 tons.[27] A bright flash and a deafening sound were observed for 300 km. Estimated explosive yield of 10 kt equivalent.[28]
Norton County bolide. One of the 5 largest meteorite falls of the 20th century, with more than 1 ton of fragments collected.[29] A brilliant fireball appeared in the sky. Then there was a loud explosion as the meteor broke apart.[30]
The Prince Edward Islands bolide was detected infrasonically about 1,100 km (680 mi) W-SW from the Prince Edward Islands off the coast of South Africa by a U.S. Government instrument network for detecting atmospheric explosions.[33] The event "did not have independent confirmation from other techniques. It remains possible that this event was not a bolide but rather another source.".[34] Washington DC Nov 1963 "Despite those earlier denials, the Defense Department now concedes that a mysterious explosion in the Antarctic last August could have been a secret nuclear blast."[35]
Revelstoke bolide. It exploded brilliantly and detonations were heard up to 130 km away.[36] About 1 g of meteorite found. Sometimes placed in SE Canada on May 31.[37][34]
Vilna bolide. Photographed.[39] Its detonation was also clearly recorded by the seismograph of the Univ. of Alberta.[40] Two very small fragments < 1 g found and stored by the university.[41]
Allende bolide. The 3rd largest meteorite fall of the 20th century. A huge, brilliant fireball lit the sky and ground for hundreds of miles. It exploded and broke up. About 2 tons of fragments were later found.[42]
Jilin bolide. The 2nd largest meteorite fall of the 20th century (after the Sikhote-Alin event). A fireball larger than the full moon was seen. There were several explosions then a violent breakup.[44] It yielded a piece at 1770 kg, more than twice the Chelyabinsk meteorite (654 kg), and total fragments collected was about 4 tons.[45]
Cando event. An unexplained ground explosion at 7:15 UTC. Topsoil and large trees were thrown tens of metres away. No fragments found and there are problems with the trajectory. It might not be an impact event.[50]
Marshall Islands fireball (about 9 ± 5 meters in diameter). Two fragments exploded at 34 km and 21 km of altitude. This impact was observed by space-based sensors both in infrared (by the DOD) and visible wavelength (by the DOE).[51]
An airburst detected in El Paso and Las Cruces. The fireball traveled S-SE before disintegrating 10–15 miles above the surface with a loud explosion, traveling around 30,000 MPH. Luminosity is described only as "a very bright flash of light, bright orange-red, similar to a distant sunset".[52]
One airburst at 46 km, three more breakups detected between 25 and 30 km. No remains found so far. Yield only based on luminosity, i.e. the total energy might have been considerably larger.[53]
Kunya-Urgench bolide. One of the 5 largest meteorite falls of the 20th century, with more than 1 ton of fragments collected.[54] A large bolide brightened the sky, and a loud whistling then a crashing noise was heard.[55][56]
The Kendrapara bolide is notable as it may have caused injuries.[66][67] A bright light then a loud noise that shattered windows. One part of the fireball fell in a village and may have set a hut on fire, injuring two people.[68]
Asteroid 7–10 meters in diameter. Coordinates are for dust trail observed after event by NASA's Aqua satellite and LIDAR in Davis Station. Event was also observed by military satellites and infrasound stations.[69]
Bolide that was observed as far as northern Lapland.[70] Meteoritic material was suspected to have landed southeast of Oulu but none has been found.[citation needed]
Chelyabinsk meteor, about ~20 meters in diameter.[82] Largest meteor airburst known since Tunguska in 1908. More than a ton of fragments found, one large piece called the Chelyabinsk meteorite.
Potentially interstellar originating from an unbound hyperbolic orbit based on an eccentricity of 2.4, an inclination of 10°, and a speed of 43.8 km/s when outside of the Solar System.[89] This would make it notably faster than ʻOumuamua which was 26.3 km/s when outside the Solar System. The meteor is estimated to have been 0.9 meters in diameter.
Sariçiçek meteorite. A bright fireball was seen and then heard as it exploded over a Turkish village.[94] More than 15 kg of fragments were found and villagers made an est. $300,000 selling the space rocks.[95]
A meteoroid weighing a few hundred kg exploded in an airburst and dropped tens of kg of meteorites into a remote area of Finnish Lapland.[98] The resulting shockwave was felt on the surface.[99] The event was detected by 7 infrasound stations.[100]
The asteroid likely had a diameter of 2–5 meters prior to impact. But because it happened in a remote area in Kamchatka, there were likely no eyewitnesses. The event was detected at 11 CTBTO infrasound stations.[101]
Asteroid (~8 meters in diameter) impacting at a relatively slow 13.6 km/s. Largest known impact since 2018 December 18.
After 2005, but not in JPL reports.
Note: For sorting purposes, location is given in "general:specific" format. For example, "Europe: Spain". This table contains a chronological list of events with a large yield at least 3 kilotons since 2005, with earlier or smaller events included if widely covered in the media.
Airbursts per year
As of January 2020, the number of airbursts each year since 2005, as reported in the JPL Fireball and Bolide Reports are:[15]
^Unsalan, O.; Bayatlı, A.; Jenniskens, P. (2020). "Earliest evidence of a death and injury by a meteorite". Meteoritics & Planetary Science. 55 (4). Wiley Online Library: 886–894. Bibcode:2020M&PS...55..886U. doi:10.1111/maps.13469. S2CID219073273.
^Halliday, Ian (December 1966). "The Bolide of September 17, 1966". Journal of the Royal Astronomical Society of Canada. 60: 257. Bibcode:1966JRASC..60..257H.
^Folinsbee, R. E.; Bayrock, L. A.; Cumming, G. L.; Smith, D. G. W. (1969). "Vilna Meteorite-Camera, Visual, Seismic and Analytic Records". Journal of the Royal Astronomical Society of Canada. 63: 61. Bibcode:1969JRASC..63...61F.
^J.A. Docobo, R.E. Spalding, Z. Ceplecha, F. Diaz-Fierros, V. Tamazian, Y. Onda, "Investigation of a bright flying object over northwest Spain, 1994 January 18", Meteoritics & Planetary Science, Vol. 33.
^Brooymans, Hanneke (November 22, 2008). "Hunt on for space rock". The Vancouver Sun. The Edmonton Journal. Archived from the original on December 10, 2008. Retrieved 2008-11-24.
^"Meteor in Quebec, Ontario". 2013-11-28. Archived from the original on 2013-12-03. Retrieved 2013-11-29. Jaymie Matthews, professor of astrophysics at the University of British Columbia, says a meteor was likely the cause of a strange boom heard Tuesday night in Quebec and Ontario
^"'Huge flash of blue light' spotted around Montreal, Ottawa most likely a meteor". The Globe and Mail. Toronto. 2013-11-27. Archived from the original on 2013-11-27. Retrieved 2013-11-29. Reports have come from throughout the Ottawa region, through Montreal, Laval, and as far south as upper New York state, near the city of Plattsburgh, he said. There have been no reports of damage.
^https://www.youtube.com/watch?v=3RavHx9peVM Meteor Meteor over Bangkok, Thailand, 7 September 2015, youtube.com (video 00:51, 7 sights, review of youtube) 07 September 2015, retrieved 08 September 2015.
^https://www.youtube.com/watch?v=tvBWiz7z6_Y Meteor Fireball Falls in Bangkok Thailand 09/07/201 (Different Angles) VIDEO, youtube.com (video 04:04, 2 sights, repeated) 07 September 2015, retrieved 08 September 2015.
