Over 7,200 damaged buildings, collapsed factory roof, shattered windows
The Chelyabinsk meteor was a near-Earth asteroid that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC), with a speed of 19.16 +/- 0.15 kilometres per second (60,000 - 69,000 km/h or 40,000 - 42,900 mph), almost 60 times the speed of sound. It quickly became a brilliant superbolidemeteor over the southern Ural region. The light from the meteor was brighter than the Sun, even at 100 km distance. It was observed over a wide area of the region and in neighbouring republics. Eyewitnesses also felt intense heat from the fireball.
The object was undetected before its atmospheric entry, in part because its radiant was close to the Sun. Its explosion created panic among local residents and about 1,500 people were injured seriously enough to seek medical treatment. All of the injuries were due to indirect effects rather than the meteor itself, mainly from broken glass from windows that were blown in when the shock wave arrived, minutes after the superbolide's flash. Some 7,200 buildings in six cities across the region were damaged by the explosion's shock wave, and authorities scrambled to help repair the structures in sub-zero (°C) temperatures.
With an estimated initial mass of about 12,000–13,000 metric tonnes (13,000–14,000 short tons, heavier than the Eiffel Tower), and measuring about 20 metres in diameter, it is the largest known natural object to have entered Earth's atmosphere since the 1908 Tunguska event that destroyed a wide, remote, forested area of Siberia. The Chelyabinsk meteor is also the only meteor confirmed to have resulted in a large number of injuries.
The earlier-predicted close approach of another, larger asteroid that same day, the roughly 30-metreDuende (at the time still known by its provisional designation2012 DA14) occurred about 16 hours later; the very different orbits of the two objects showed they were unrelated to each other.
The event began at 09:20:21 Yekaterinburg time, several minutes after sunrise in Chelyabinsk, and minutes before sunrise in Yekaterinburg. According to eyewitnesses, the bolide appeared brighter than the sun, as was later confirmed by NASA. An image of the object was also taken shortly after it entered the atmosphere by the weather satellite Meteosat 9. Witnesses in Chelyabinsk said that the air of the city smelled like gunpowder.
Illustrating all "phases", from atmospheric entry to explosion.
The visible phenomenon due to the passage of an asteroid or meteoroid through the atmosphere is called a meteor. If the object reaches the ground, then it is called a meteorite. During the Chelyabinsk meteoroid's traversal, there was a bright object trailing smoke, then an air burst (explosion) that caused a powerful shock wave, the cause of the damage to thousands of buildings in Chelyabinsk and its neighbouring towns. The fragments entered dark flight (without the emission of light) and created a strewn field of numerous meteorites on the snow-covered ground (officially named Chelyabinsk meteorites).
According to the Russian Federal Space Agency, preliminary estimates indicated the object was an asteroid moving at about 30 km/s in a "low trajectory" when it entered Earth's atmosphere. According to the Russian Academy of Sciences, the meteor then pushed through the atmosphere at a velocity of 15 km/s. The radiant (the apparent position of origin of the meteor in the sky) appears from video recordings to have been above and to the left of the rising Sun.
The United States space agency NASA estimated the diameter of the bolide at about 17–20 m and has revised the mass several times from an initial 7,700 tonnes (7,600 long tons; 8,500 short tons), until reaching a final estimate of 10,000 tonnes, (11,000 short tons, greater than the total weight of the Eiffel Tower). The air burst and shock wave registered on seismographs at magnitude 2.7. On 1 March 2013 NASA published a detailed synopsis of the event, stating that at peak brightness (at 09:20:33 local time), the meteor was 23.3 km (14.5 miles, 76,000 feet) high, located at 54.8°N, 61.1°E. At that time it was travelling at about 18.6 km/s (11.6 mi/s), (about 67,000 km/h, or about 41,750 mph) —almost 60 times the speed of sound.
This visualization shows the aftermath observations by NASA satellites and computer models projections of the plume and meteor debris trajectory around the atmosphere.
The infrasound waves given off by the explosions were detected by 20 monitoring stations designed to detect nuclear weapons testing run by the Comprehensive Test Ban Treaty Organization Preparatory Commission, including at the distant Antarctic station, some 15,000 kilometres (9,300 mi) away. The blast of the explosion was large enough to generate infrasound returns, after circling the globe, at distances up to about 85,000 kilometres (53,000 mi). Multiple arrivals involving waves that traveled twice around the globe have been clearly identified. A preliminary estimate of the explosive energy using empirical period-yield scaling relations gives a value of 460 kilotons of TNT equivalent. The meteor explosion produced the largest infrasounds ever to be recorded by a United Nations monitoring system, so great that they reverberated around the world several times, taking over a day to dissipate. Additional scientific analysis of US military infrasound data was aided by an agreement reached with US authorities to allow its use by civilian scientists, implemented only about a month before the Chelyabinsk meteor event.
Early analysis of CCTV and dashcam video posted online indicated that the meteor approached from east by south, and exploded about 40 km south of central Chelyabinsk above Korkino at a height of 23.3 km (14.5 miles, 76,000 feet), with fragments continuing in the direction of Lake Chebarkul. In November 2013, results were published based on a more careful calibration of dash cam videos in the field weeks after the event during a Russian Academy of Sciences field study, which put the point of peak brightness at 29.7 km altitude and the final disruption of the thermal debris cloud at 27.0 km, settling to 26.2 km, all with a possible systematic uncertainty of +/- 0.7 km.
The last time a similar phenomenon was observed in the Chelyabinsk region was the Kunashak meteor shower of 1949, after which scientists recovered about 20 meteorites weighing over 200 kg in total. The Chelyabinsk meteor is thought to be the biggest natural space object to enter Earth's atmosphere since the 1908 Tunguska event, and the only one confirmed to have resulted in a large number of injuries,[Note 1] although a small number of panic-related injuries occurred during the Great Madrid Meteor Event of 10 February 1896.
Strewnfield map of recovered meteorites (253 documented find locations, status of 18 July 2013).
In the hours following the visual meteor sighting, a 6-metre (20 ft) wide hole was discovered on Lake Chebarkul's frozen surface. It was not immediately clear if this was the result of an impact, however, scientists from the Ural Federal University collected 53 samples from around the hole the same day it was discovered. The early specimens recovered were all under 1 centimetre (0.39 in) in size and initial laboratory analysis confirmed their meteoric origin. They are ordinary chondrite meteorites and contain 10% iron. The official name for such fragments is designated as Chelyabinsk meteorite. The Chelyabinsk meteor was later determined to come from the LL chondrite group.
In June 2013, Russian scientists reported that further investigation by magnetic imaging below the location of the ice hole in Lake Chebarkul had identified a 60-centimetre (2.0 ft)-size meteorite buried in the mud at the bottom of the lake. Before recovery began, the chunk was estimated to weigh roughly 300 kilograms (660 lb).
Following an operation lasting a number of weeks, it was raised from the bottom of the Chebarkul lake on 16 October 2013. With a total mass of 654 kg (1,442 lb) this is the largest found fragment of the Chelyabinsk meteorite. Initially, it tipped and broke the scales used to weigh it, splitting into three pieces.
In November 2013, a video from a security camera was released showing the impact of the fragment at the Chebarkul lake. This is the first recorded impact of a meteorite on video. From the measured time difference between the shadow generating meteor to the moment of impact, scientists calculated that this meteorite hit the ice at about 225 meters per second, 64 percent of the speed of sound.
In the days immediately after the initial visual meteor sighting, officials in the neighbouring country of Kazakhstan said they were looking for two possible unidentified objects that may have impacted in Aktobe Province, adjacent to the affected Russian regions. To date, no further announcements have been made.
Injuries and damage
Shattered windows in the foyer of the Chelyabinsk Drama Theatre
The blast caused by the meteor's air burst caused a considerable number of injuries. Russian authorities stated that 1,491 people, including 311 children, sought medical attention in Chelyabinsk Oblast within the first few days. Health officials said 112 people had been hospitalised, with two in serious condition. A 52-year-old woman with a broken spine was flown to Moscow for treatment. Most people were hurt by shattered, falling or blown-in glass. The intense light from the meteor, momentarily 30 times brighter than the Sun, led to over 180 cases of eye pain, and 70 people subsequently reported temporary flash blindness. Twenty people reported ultraviolet burns similar to sunburn, possibly intensified by the presence of snow on the ground.
A fourth-grade teacher in Chelyabinsk, Yulia Karbysheva, was hailed as a hero after saving 44 children from imploding window glass cuts. Despite not knowing the origin of the intense flash of light, Karbysheva thought it prudent to take precautionary measures by ordering her students to stay away from the room's windows and to perform a duck and cover maneuver. Karbysheva, who remained standing, was seriously lacerated when the blast arrived and window glass severed a tendon in one of her arms; however, none of her students, whom she ordered to hide under their desks, suffered cuts.
After the air blast, car alarms went off and mobile phone networks were overloaded with calls. Office buildings in Chelyabinsk were evacuated. Classes for all Chelyabinsk schools were cancelled, mainly due to broken windows. At least 20 children were injured when the windows of a school and kindergarten were blown in at 09:22. Following the event, government officials in Chelyabinsk asked parents to take their children home from schools.
The collapsed roof over the warehouse section of a zinc factory in Chelyabinsk
Approximately 600 m2 (6,500 sq ft) of a roof at a zinc factory collapsed during the incident. Residents in Chelyabinsk whose windows were smashed quickly sought to cover the openings with anything available, to protect themselves against temperatures of −15 °C (5 °F). Approximately 100,000 home-owners were affected, according to Chelyabinsk Oblast Governor Mikhail Yurevich. He also said that preserving the water pipes of the city's central heating system was the primary goal of the authorities as they scrambled to contain further post-explosion damage.
By 5 March 2013 the number of damaged buildings was tallied at over 7,200, which included some 6,040 apartment blocks, 293 medical facilities, 718 schools and universities, 100 cultural organizations, and 43 sport facilities, of which only about one and a half percent had not yet been repaired. The oblast's governor estimated the damage to buildings at more than 1 billion rubles (approximately US$33 million). Chelyabinsk authorities said that broken windows of apartment homes, but not the glazing of enclosed balconies, would be replaced at the state's expense. One of the buildings damaged in the blast was the Traktor Sport Palace, home arena of Traktor Chelyabinsk of the Kontinental Hockey League (KHL). The arena was closed for inspection, affecting various scheduled events, and possibly the postseason of the KHL.
Colonel General Nikolay Bogdanov, commander of the Central Military District, created task forces that were directed to the probable impact areas to search for fragments of the asteroid and to monitor the situation. Meteorites (fragments) measuring 1 to 5 cm (0.39 to 1.97 in) were found 1 km (0.62 mi) from Chebarkul in the Chelyabinsk region.
The Russian government put out a brief statement within an hour of the event, but the event was first covered in the US by hockey blog Russian Machine Never Breaks. Heavy coverage by the international media had begun by the time the Associated Press put out a brief report with the Russian government's confirmation less than two hours afterwards. Less than 15 hours after the meteor impact, videos of the meteor and its aftermath had been viewed millions of times.
The number of injuries caused by the asteroid led the Internet-search giant Google to remove a Google Doodle from their website, created for the predicted pending arrival of another asteroid, 2012 DA14. New York City planetarium director Neil deGrasse Tyson stated the Chelyabinsk meteor was unpredicted because no attempt had been made to find and catalogue every 15-metrenear-Earth object. In television media interviews shortly afterwards Tyson also noted the disturbing closeness of the two completely unrelated events.
On 27 March 2013 a broadcast episode of NOVA titled "Meteor Strike" documented the Chelyabinsk meteor, including the large amounts of meteoritic science revealed by the numerous videos of the airburst posted online by ordinary citizens. The NOVA program called the video documentation and the related scientific discoveries of the airburst "unprecedented". The documentary also discussed the much greater tragedy "that could have been" had the asteroid entered the Earth's atmosphere more steeply.
Impactor orbital parameters
Preliminary orbital solutions for impacting asteroid
The asteroid belonged to the Apollo group of near-Earth asteroids, and was roughly 40 days past perihelion (closest approach to the Sun) and had aphelion (furthest distance from the Sun) in the asteroid belt. Several groups independently derived similar orbits for the object, but with sufficient variance to point to different potential parent bodies of this meteoroid. The Apollo asteroid2011 EO40 was initially proposed as a likely candidate for the role of the parent body of the Chelyabinsk superbolide. The more recently published orbits are similar to the 2-kilometer-diameter asteroid (86039) 1999 NC43 to suggest they had once been part of the same object.
In the aftermath of the air burst of the body, a large number of small meteorites fell on areas west of Chelyabinsk, generally at terminal velocity, about the speed of a piece of gravel dropped from a skyscraper. Analysis of the meteor showed that all resulted from the main breakup at 34–27 km altitude. Local residents and schoolchildren located and picked up some of the meteorites, many located in snowdrifts, by following a visible hole that had been left in the outer surface of the snow. Speculators have been active in the informal market that has rapidly emerged for meteorite fragments.
On the first anniversary of this event, 15 February 2014, during the 2014 Winter Olympics in Sochi, in addition to their Olympic medals, the day's ten gold medalists were also given special commemorative medals which featured fragments of the Chelyabinsk meteorite. Although there were only seven different medal events, one was a team event. Winners included:
^ abcdeZuluaga, Jorge I.; Ferrin, Ignacio (2013). "A preliminary reconstruction of the orbit of the Chelyabinsk Meteoroid". arXiv:1302.5377 [astro-ph.EP]. "We use this result to classify the meteoroid among the near Earth asteroid families finding that the parent body belonged to the Apollo asteroids.".
Brown, P. G.; Assink, J. D.; Astiz, L.; Blaauw, R.; Boslough, M. B.; Borovička, J.; Brachet, N.; Brown, D.; Campbell-Brown, M.; Ceranna, L.; Cooke, W.; de Groot-Hedlin, C.; Drob, D. P.; Edwards, W.; Evers, L. G.; Garces, M.; Gill, J.; Hedlin, M.; Kingery, A.; Laske, G.; Le Pichon, A.; Mialle, P.; Moser, D. E.; Saffer, A.; Silber, E.; Smets, P.; Spalding, R. E.; Spurný, P.; Tagliaferri, E. et al. (2013). "A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors". Nature503 (7475): 238–241. Bibcode:2013Natur.503..238B. doi:10.1038/nature12741.
"Meteor Strike". NOVA documentary broadcast, 53 minutes, aired 27 March 2013. PBS. "Includes extensive scientific analysis of the worldwide infrasound monitoring network data from which the megaton energy estimates were made."