The Tschebarkul 2013 super bolide, Tscheljabinsk, Russia – what do we currently know?
Explosion and impact of the meteor: In the meantime the commotion has died down and has given way to more factual information and scientific relevance, and here on our website we would like to dedicate sufficient coverage of the current knowledge.
Such an event that we have now witnessed in Russia undoubtedly highlights also the Chiemgau impact and the related discussions about the impact parameters like the kind of impactor, fragmentation in the atmosphere and the dimensions of the strewn field.
Source: Svetlana Korzhava; WIKIMEDIA COMMONS
Important information is coming directly from Russia where as is well known good scientific relations of the CIRT exist, and we thank particularly Dr. Slava Gusiakov from the Holocene Impact Working Group for his personal communication.
On February 2, 2013, at 7:20:26 local time (3:20:26 UT) a meteor appeared above the Čeljabinsk district (at the Miass river, central/southern Urals).
The blast wave of the impact resulted in considerable damage of 4715 buildings (first of all 200,000 m2 glass slabs) and in consequence in 1,240 injured persons (42 of them had to be taken to a hospital). The caused damages are estimated to amount to a billion of rubles (about 33 millions of USD). 4660 persons and 1047 vehicles were engaged in rescue operations.
Even more than one week after the event no unambiguous and exact statements about the trajectory of the object, its provenance from the planetary system and its properties are possible.
Various data have been collected from seismographs of the USGS, from infrasound measurements of the CTBTO, from weather satellites (e.g., Meteosat-9, Meteosat-10, Fengýun 2-05. MTSAT-2), from video recording (Dash-Cams), from eyewitness reports (laymen, pilots of airliners) and ground prospection (police, research teams) and have been integrated in the ongoing evaluation. Meteosat 9 and 10 photographed the meteoroid’s trace in the atmosphere. In addition, the Chinese satellite Fengýun 2-05 took an infrared photo. The Japanese satellite MTSAT-2 was able to delineate the trace still nine hours after the event and measured a temperature of -31°C distinctly exceeding that of the ambient atmosphere (-108°C).
After all, the existing measurement data and the eyewitness reports enable to get a certain picture of the event. In any case, the research campaigns of the next months will certainly deepen the current issues, but many an insight will also have to be reassessed here and there.
The trajectory of the meteoroid is in part differently described. According to the Russian Academy of Science (http://www.ras.ru/news/shownews.aspx?id=1da2959b-902f-46b2-9f1f-0c62d19740e8#content) the meteoroid (mass about 10 t) entered the atmosphere at a velocity of 15-20 km/s and burst at an altitude between 50 and 30 km. At an altitude of 15-5 km the maximum energy of 100-200 kt (TNT equivalent) was released.
According to Sergejs Zaharova (Russian Geographical Society) the meteoroid came from southeast and traveled to northwest (ca. 290° azimuth) corresponding to a trajectory from Jemanschelinsk (54° 45′ 0″ N, 61° 19′ 0″ E) to Miass (55° 0′ 0″ N, 60° 6′ 0″ E). Eyewitnesses report that the meteoroid “came out of the sun”.
Following the current NASA information (http://www.nasa.gov/mission_pages/asteroids/news/asteroid20130215.html) the object is said to have flared at an altitude of ca. 25 – 15 km. The angle of trajectory was less than 20°. Its diameter was about 17 m and it weighted 7,000 – 10,000 t. On entering the atmosphere the velocity was 18 km/s (64,800 km/h). For 32.5 s the meteoroid passed the atmosphere before breaking into pieces. The energy released by the air burst was about 500 kt (TNT equivalent).
Infrasound test points of the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization) had located significant infrasound emissions in the Urals region, and as far as Alaska, 6,500 km away from Tscheljabinsk, sufficient data could be attained. From these data size and mass of the object were estimated to be approx. 15 m and 7,000 t. (Peter Brown, University of Western Ontario, Canada).
According to Zuluaga, Jorge I. and Ferrin, Ignacio: A preliminary reconstruction of the orbit of the Chelyabinsk Meteoroid. 1302, 2013, S. 5377. arXiv:1302.5377. Bibcode: 2013arXiv1302.5377Z the meteor flared at dawn at an altitude between 47 and 32 km. The radiant was located in the Pegasus constellation and rose near the sun upper left on the eastern horizon.
On passage of the atmosphere and particularly on fragmentation a super bolide of more than sun brightness (-26 mag) developed by ionization of the air and ablation of the material. Multiple detonations (three at least) could be heard the first of which was the loudest. The first explosion lasted five seconds, then a blast wave followed that after ca. 1 minute reached the ground and caused the greatest damage. Distinct light and fume trails could be observed in the sky. In addition, a strong hiss (an electromagnetic phenomenon in the atmosphere) was heard. The center of the detonation was located above the south of Tscheljabinsk in the district of Jemanschelinsk – Juschnouralsk. One kilometer southwest of the center of Tscheljabinsk the blast wave caused a ground shaking like a 2.7 magnitude earthquake (15.2.2013, 03:20:26 GMT). For comparison: The Tunguska event in 1908 had a 5.0 earthquake magnitude.
The damage of buildings extended over 25,000-30,000 km2. The air burst could be observed over 600,000 km2 with the naked eye. The visible trajectory was 400-500 km in length.
According to the available data the meteoroid moved along an elliptical trajectory the aphelion of which extended beyond Mars orbit (source: NASA). It is assumed that the object belonged to the group of the Apollo asteroids. The orbit data so far computed by three authors (American Meteor Society http://www.amsmeteors.org/2013/02/large-daytime-fireball-hits-russia/, IAU http://www.webalice.it/mizar02/articoli/Meteorb.dat; Zuluaga et al. 2013 http://adsabs.harvard.edu/abs/2013arXiv1302.5377Z) are matching quite well (http://en.wikipedia.org/wiki/2013_Russian_meteor_event#cite_note-USGS-41).
Existence, size and spreading of possible impact craters is so far unsettled. Up to now (Febr. 26, 2013) three impact points are known, two near Tschebarkul and one in Slatoust.
A larger fragment is said to have produced a distinct circular 8 m-diameter hole in the ice of Lake Tschebarkul (about 1 km away from the Tschebarkul city and 80 km away from the Tscheljabinsk city). Estimated at a size of 60 cm it was however not found as yet with dives. Reportedly, fishermen observed the impact of seven larger fragments, one of them into the lake. Presently, the ice of the lake is 30 cm thick only. The impact into the lake is said to have lifted the water by 3-4 m.
A second impact point is reported from near Slatost, a town 112 km northwest of the Tscheljabinsk city.
The air blast affected Perwomaiski near Korkino (30 km away from Tscheljabinsk), Deputatskiy, Jemanschelinsk (44 km away from Tscheljabinsk).
In the Etkulskom district a meteorite shower occurred. Meanwhile more than 100 fragments (the size of a fist) with an overall mass of ca. 1 kg have been sampled south of Tscheljabinsk (probably in the Etkulskom district).
It is still unverified whether other bolides that were observed in the northern hemisphere around Febr. 15, 2013, are related with the Tschebarkul super bolide.
The material from the Lake Tschebarkul area has been analyzed scientifically. Local geologists (e.g., Viktor Grokhovsky, Urals Federal University) confirmed the extraterrestrial origin for 53 smaller fragments (0.5 – 1 cm) exhibiting a distinct melt crust. They belong to the stone meteorites (regular chondrites) with more than 10 % iron and nickel content. Moreover they contain (latest data, March 2, 2013) as main minerals olivine (Mg, Fe) 2SiO4 and orthopyroxen (Mg, Fe) 2Si2O6, and in smaller quantities troilite FeS, heazlewoodite Ni3S2, kamacite und taenite Ni, Fe, chromite (Fe, Mg) Cr2O4, clinopyroxen CaMgSi2O6, plagioclase (Ca, Na) Al2Si2O8, and a glass.
On Febr. 25, 2013, a fragment weighing 1.8 kg was sampled near Jemanschelinsk and the Trawniki settlement. The composition corresponds to that of the Lake Tschebarkul meteorites.
Implications and significance
In the 20th century the Tunguska, Russia (1908), 10-15 Mt TNT, Rio Curaca, Brazil, (1930), 100 kt – 1 Mt, and Arroyomolinos de León, Spain (1932) 190 kt, super bolides were observed.
As for the 21st century we refer to Benghazi, Libya (2009), 12-20 kt and South Sulawesi, Indonesia (2009), 31-50 kt, and now we are confronted with Tschebarkul, Russia, and 500 kt.
The Tschebarkul 2013 event visualizes very plainly, although in a more moderate way, what happened when the Chiemgau impact took place. Particularly comparable are the high altitude of fragmentation, the low angle of entry und the trajectory apparently coming out of the sun. This latter statement reminds of the Phaethon myth and thus confirms the detailed descriptions obviously based on eyewitness reports at that time.
References and images:
Zuluaga et al. 2013 http://adsabs.harvard.edu/abs/2013arXiv1302.5377Z)