Over 7,200 damaged buildings, collapsed factory roof, shattered windows
The Chelyabinsk meteor was a superbolide caused by 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). 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-metre367943 Duende (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", "sulfur" and "burning odors" starting about 1 hour after the fireball and lasting all day.
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 blast 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).
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.
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.
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. 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. 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 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's blast wave, when it hit the ground, produced a seismic wave which registered on seismographs at magnitude 2.7.
The Russian Geographical Society said the passing of the meteor over Chelyabinsk caused three blasts of different energy. The first explosion was the most powerful, and was preceded by a bright flash, which lasted about five seconds. Initial newspaper altitude estimates ranged from 30–70 km, with an explosive equivalent, according to NASA, of roughly 500 kilotonnes of TNT (2,100 TJ), although there is some debate on this yield. (500 kt is exactly the same energy released by the Ivy King nuclear explosion in 1952). According to a paper in 2013 however, all these ~500 kiloton yield estimates for the meteor airburst are "uncertain by a factor of two because of a lack of calibration data at those high energies and altitudes."
The hypocentre of the explosion was to the south of Chelyabinsk, in Yemanzhelinsk and Yuzhnouralsk. Due to the height of the air burst, the atmosphere absorbed most of the explosion's energy. The explosion's blast wave first reached Chelyabinsk and environs between less than 2 minutes 23 seconds and 2 minutes 57 seconds later. The object did not release all of its kinetic energy in the form of a blast wave as some 90 kilotons of TNT(about 3.75 x 1014 joules, or 0.375 PJ) of the total energy of the main airburst's fireball was emitted as visible light according to NASA's Jet Propulsion Laboratory, and two main fragments survived the primary airburst disruption at 29.7 km, they flared around 24 km, with one falling apart at 18.5 km and the other remaining luminous down to 13.6 km, moreover as part of the meteoroid continued on its general trajectory downward it retained a small fraction of its initial kinetic energy to punch a hole in the frozen Lake Chebarkul, an impact that was fortuitously captured on camera and released in November 2013.
This visualization shows the aftermath observations by NASA satellites and computer models projections of the plume and meteor debris trajectory around the atmosphere. The plume rose to an altitude of 35 km and once there, it was rapidly blown around the globe by the polar night jet.
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. The meteor explosion produced the largest infrasounds ever to be recorded by the United Nations(CTBTO) infrasound monitoring system, which began recording in 2001, 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.
A preliminary estimate of the explosive energy by Astronomer Boris Shustov, director of the Russian Academy of Sciences Institute of Astronomy, was 200 kilotonnes of TNT (840 TJ), another using empirical period-yield scaling relations and the infrasound records, by Peter Brown of the University of Western Ontario gave a value of 460–470 kilotonnes of TNT (1,900–2,000 TJ) and represents a best estimate for the yield of this airburst, however there remains a potential "uncertainty [in the order of] a factor of two in this yield value". Brown and his colleagues also went on to publish a paper in November 2013 which stated that the "widely referenced technique of estimating airburst damage does not reproduce the [Chelyabinsk] observations, and that the mathematical relations found in the book The Effects of Nuclear Weapons which are based on the Effects of nuclear weapons—[which is] almost always used with this technique—overestimate blast damage[when applied to meteor airbursts]. A similar overestimate of the explosive yield of the Tunguska airburst also exists, as incoming celestial objects have rapid directional motion, the object causes stronger blast wave and thermal radiation pulses at the ground surface than would be predicted by a stationary object exploding, limited to the height at which the blast was initiated-where the objects "momentum is ignored". Thus a meteor airburst of a given energy is "much more damaging than an equivalent [energy] nuclear explosion at the same altitude." The seismic wave produced when the primary airburst's blast struck the ground yields a rather uncertain "best estimate" of 430 kilotons(momentum ignored). Corresponding to the seismic wave which registered on seismographs at magnitude 2.7.
Brown also states that the double smoke plume formation, as seen in photographs, is believed to have coincided near the primary airburst section of the dust trail(as also pictured following the Tagish Lake fireball), and it likely indicates where rising air quickly flowed into the center of the trail, essentially in the same manner as a moving 3D version of a mushroom cloud. Photographs of this smoke trail portion, prior to it splitting into two plumes, depict this cigar shaped region glowing incandescently for a few seconds. This region is the area in which the maximum of material ablation occurred, with the double plume persisting for a time and then appearing to rejoin or close up.
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 created by the meteor's air burst produced extensive ground damage over an irregular elliptical area a few tens of kilometres across, with the secondary effects of the blast being the main cause of the 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. However most of the injured were hurt by the secondary blast effects, that is the shattered, falling or blown-in glass. The intense light from the meteor, momentarily 30 times brighter than the Sun, also produced injuries, leading 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. Vladimir Petrov, when meeting with scientists to assess the damage, reported that he sustained so much sunburn from the meteor that the skin flaked only days later.
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 is one of the candidates proposed for the role of the parent body of the Chelyabinsk superbolide. Other published orbits are similar to the 2-kilometer-diameter asteroid (86039) 1999 NC43 to suggest they had once been part of the same object; however, they may not be able to reproduce the timing of the impact.
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:
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