The Kosice meteorite fall: Recovery and strewn field

Transcription

1 Meteoritics & Planetary Science 50, Nr 5, (2015) doi: /maps The Kosice meteorite fall: Recovery and strewn field Juraj T OTH 1*,Jan SVORE N 2,Jirı BOROVI CKA 3, Pavel SPURN Y 3, Antal IGAZ 4, Leonard KORNO S 1, Peter VERE S 1,5, Marek HUS ARIK 2,Julius KOZA 2, Ales KU CERA 2, Pavel ZIGO 1, Stefan GAJDO S 1, Jozef VIL AGI 1, David CAPEK 3, Zuzana KRI SANDOV A 2, Dusan TOMKO 2,Jirı SILHA 1,6, Eva SCHUNOV A 1,5, Marcela BODN AROV A 2, Diana B UZOV A 7, and Tereza KREJ COV A 2,8 1 Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava 84248, Slovakia 2 Astronomical Institute, Slovak Academy of Sciences, Tatranska Lomnica 05960, Slovakia 3 Astronomical Institute, Czech Academy of Sciences, Ondrejov 25165, Czech Republic 4 Hungarian Astronomical Association, MCSE, P.O. Box 219, H-146,1 Budapest, Hungary 5 Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, Hawai i 96822, USA 6 Astronomical Institute, University of Bern, Bern, Switzerland 7 Department of Adaptation Biotechnologies, Global Change Research Centre AS CR, Drasov, Czech Republic 8 Department of Theoretical Physics and Astrophysics, Masaryk University, Brno 1137, Czech Republic * Corresponding author. toth@fmph.uniba.sk (Received 22 July 2014; revision accepted 08 February 2015) Abstract We provide the circumstances and details of the fireball observation, search expeditions, recovery, strewn field, and physical characteristics of the Kosice meteorite that fell in Slovakia on February 28, The meteorite was only the 15th case of an observed bolide with a recovered mass and subsequent orbit determination. Despite multiple eyewitness reports of the bolide, only three videos from security cameras in Hungary were used for the strewn field determination and orbit computation. Multiple expeditions of professionals and individual searchers found 218 fragments with total weight of 11.3 kg. The strewn field with the size of km is characterized with respect to the space distribution of the fragments, their mass and size-frequency distribution. This work describes a catalog of 78 fragments, mass, size, volume, fusion crust, names of discoverers, geographic location, and time of discovery, which represents the most complex study of a fresh meteorite fall. From the analytical results, we classified the Kosice meteorite as an ordinary H5 chondrite. INTRODUCTION The recovery of a meteorite is still a rare event compared to an actual influx of interplanetary matter into the atmosphere from cm to meter size range. The recovery is also a final step to obtain interplanetary material for complex laboratory analyzes. Moreover, the significance of such an event is underlined in case of an instrumentally observed fall. The Kosice meteorite represents only the 15th case in history when a bolide was observed, fall area computed, and actual fragments were found (Toth and Svoren 2010; Borovicka et al. 2013; Meteoritical Bulletin Database). The chain of subsequent events worked well in the Kosice case as discussed in the following chapters. In the past, there have been only five known meteorites recovered in Slovakia before the Kosice meteorite. Four of them were found in the 19th century (Lenartov, Magura, Gross-Divina, Nagy-Borove) and one in the 20th century Rumanova (Rojkovic et al. 1995, 1997). Ordinary chondrite Rumanova is a meteorite that had lain on the surface for about 12,000 years (Porubcan et al. 2010). The last observed meteorite fall in Slovakia produced an ordinary chondrite Nagy-Borove (Vel ke Borove) in In the last decade, there were several unsuccessful attempts to find fresh meteorites in Slovakia and nearby countries from observed fireballs dropping meteorites within the frame of the established European Fireball Network (Spurny et al. 2007), or a recently established Slovak 853 The Meteoritical Society, 2015.

2 854 J. Toth et al. Fig. 1. Map (Google Earth) of the Kosice meteorite fall. Instrumental detections and eye (white stars) or ear (blue stars) witnesses are depicted. Three security cameras around Budapest, Hungary directly recorded the fireball itself (cameras). Radiometers of European Fireball Network in Czech Republic and Austria recorded the lightcurve of the fireball (squares). Seismic stations, which recorded the event, are shown as triangles. The fireball is marked as a red arrow. Video Meteor Network (Toth et al. 2011). There was a search for the predicted main body of Moravka observed in 2000 (Borovicka and Kalenda 2003) in Slovakia; Turji-Remety was observed in 2001 (Spurny and Porubcan 2002) there was a search localities in Ukraine (Toth et al. 2005). Moreover, expeditions to Sasov (2006), Martin (2007), Komjatna (2010), Zlatn^o (2010), Podolie (2011), Kajarpec (2011, Hungary), and more recently at Piliscsaba (2013, Hungary) were organized, but searches were unsuccessful. Although no meteorites have been found during these expeditions organized by the Comenius University with the help of students and people from public observatories, significant field experience for subsequent and successful Kosice meteorite recovery was gained. DATA ACQUISITION THE KO SICE METEORITE CASE On February 28th at 23:24:46 local time (22:24:46 UT) a very bright bolide enlightened the night sky over Central Europe. Despite the late hour, many people witnessed an astonishing celestial spectacle. The glare of the bolide illuminated streets and the interior of apartments; in some places in Eastern Slovakia cannonlike burst or series of low frequency blasts were heard. Due to the cloudy skies and scattered showers, there were no direct images of the fireball from the European Fireball Network (Spurny et al. 2007) or from the Slovak Video Meteor Network (Toth et al. 2011). Despite this fact, the fireball was instrumentally observed, and its orbit, atmospheric trajectory, and strewn field were calculated by Borovicka et al. (2013). The following morning of March 1, 2010, many reports and video records of the fireball flash illuminating streets were released on the Internet or broadcasted by media in Slovakia and Hungary. Some of these observations are depicted in Fig. 1. The main source of video data came from two surveillance cameras from Hungary near Budapest (Orkeny village contact persons Mrs. Fazzi and Mr. Vass; Telki village contact persons Mr. Szarneczky and Mr. Kiss), which

3 Kosice meteorite fall 855 Fig. 2. Recovered 218 Kosice meteorite fragments (red dots) between villages Vysny Klatov and Kavecany (about 5 km west of the city Kosice) within the predicted strewn field area by J. Borovicka (black line) by March 11, The first meteorite was found at the southwest side of the strewn field by March 20, The size of the strewn field is km. The densest part of 90% recovered meteorites occupied area of km. The whole strewn area consisted of low ridges and valleys with the altitudes ranging from 300 to 600 m above sea level, but some slopes are steep. The strewn field is covered mostly by woods, meadows are less present. The main road from Kosice to Margecany crosses the northeast part of the strewn field, where the recreational area Alpinka is located (one of the main fragments was recovered there). directly imaged the fireball. P. Spurny contacted J. Toth just 7 h after the fireball event to obtain the calibration of videos in Hungary. J. Toth made contacts with astronomical amateurs and with several members of the Hungarian Astronomical Association (MCSE), so the first data were transferred to J. Borovicka within a few days. J. Borovicka calculated the atmospheric trajectory with the predicted strewn field by March 11. Later, a third video from Budapest appeared, which was calibrated and analyzed, but was not used in the first strewn field predictions. The strewn field estimated by J. Borovicka was located east of the village of Vysny Klatov and northwest of Kosice, a city in Eastern Slovakia (Fig. 2). He sent this information to J. Toth (Comenius University) and J. Svoren (Astronomical Institute of the Slovak Academy of Sciences). J. Toth and L. Kornos visited the predicted strewn field area on March 12 and interviewed 30 eyewitnesses in eight nearby villages. A detailed description of activities carried out by colleagues from the Comenius University and by the Astronomical Institute of the Slovak Academy of Sciences (SAS) during March 12 20, and data evaluation and summarization of results based on information obtained from witnesses can be found in a future article. Generally, the witnesses were very reliable for the validation and confirmation of instrumental data, but their reports needed to be critically reviewed and some of them even rejected as false. Moreover, we were able to gather some other testimonies (Fig. 1) from Slovakia, where thunder or cannonade-like sounds were noticed within a km radius, while over pressure was detected only under the trajectory of the fireball (e.g., in the Jasov village). EXPEDITIONS AND RECOVERY OF METEORITES By March 12, fresh snow has covered the strewn field area so no search was possible during the interviews of the eye-witnesses. As snow had melted by March 20, the first expedition (organized both by J. Svoren of the Astronomical Institute of SAS and by J. Toth of the Comenius University) took place on this day. The search area was based on Borovicka s calculations and was localized near Vysny Klatov (Fig. 2). The first meteorite (No. 1, 27.3 g, see Table 1 for more details) was found by J. Toth inside the predicted strewn field at Vysny Klatov village, just 40 min walking from its parking area. After

4 856 J. Toth et al. Table 1. Kosice meteorite the catalog of fragments with the time and date of the find, mass, size, volume, geographical position, altitude, finder name, and fusion crust coverage Fusion No. Date/Time (CET) Mass (g) Size (cm) Volume (cm 3 ) Latitude ( ) Longitude ( ) Altitude (m) Finder (name) crust (%) 1 ( ) a 504 Juraj Toth 90 11: : a 514 Diana Buzova 3 (21. 3.) , ,3 b 367 Marek Husarik 08: : , ,8 e 535 Tereza Krejcova 5 09: , ,7 e 532 Tereza Krejcova 6 12: b 349 Marek Husarik : b 348 Marek Husarik 8 12: b 333 Marek Husarik : b 332 Marek Husarik 10 12: b 334 Jan Svoren : b 334 Diana Buzova 12 13: b 336 Julius Koza : b 336 Marek Husarik 14 (23. 3.) 16: c 311 David Capek 15 17: c 328 David Capek (24. 3.) 09: a 406 Pavel Spurny : d 450 Stanislav Kaniansky 19 09: c 424 Pavel Spurny 20 10: a 460 Eva Schunova 21 10: a 493 Marcel Skreka 22 11: a 502 Dusan Tomko 23 11: a 507 Pavol Zigo : a 502 Julius Koza 25 13: a 522 Miroslav Seben 26 13: a 517 Jirı Silha 27 13: a 517 Eva Schunova : a 528 Pavol Zigo 29 14: a 520 Leonard Kornos : c 515 Marcela Bodnarova 31 14: c David Capek 32 15: a 584 Peter Veres 33 16: a 579 Marcela 85 Bodnarova 34 16: c 572 David Capek 35 16: c 486 Marcela 95 Bodnarova 36 16: d Marcel Skreka 37 (25. 3.) 09: a 444 Peter Veres 38 09: a 314 Julius Koza : a 304 Tereza Krejcova 40 10: a 443 Pavol Zigo 41 10: a 319 Jozef 95 Nedoroscık 42 10: a 319 Tereza Krejcova 43 10: a 313 Julius Koza : a 446 Juraj Toth : a 314 Zuzana Mimovicova 46 10: a 314 Zuzana Krisandova

5 Kosice meteorite fall 857 Table 1. Continued. Kosice meteorite the catalog of fragments with the time and date of the find, mass, size, volume, geographical position, altitude, finder name, and fusion crust coverage. Fusion crust (%) No. Date/Time (CET) Mass (g) Size (cm) Volume (cm 3 ) Latitude ( ) Longitude ( ) Altitude (m) Finder (name) 47 10: a 315 Julius Koza : a 313 Julius Koza 49 11: a 325 Marcela Bodnarova 50 11: a 328 Dusan Tomko 51 11: a 526 Jirı Silha : a 542 Jaromır 60 Petrzala 53 11: a 538 Eva Schunova : a 332 Zuzana 40 Krisandova 55 12: a 338 Tereza Krejcova : a 334 Dusan Tomko : a 521 Miroslav Seben : a 521 Juraj Toth : a 318 Zuzana Krisandova 60 14: a 341 Jirı Silha 61 15: d 360 Jirı Silha 62 (28. 3.) 10: , ,8 e 400 Julius Koza : , ,8 e 409 Jan Svoren 64 10: , ,0 e 416 Julius Koza (3. 4.) a 572 Stefan Gajdos a 563 Stefan Gajdos (6. 4.) 14: a 538 Tomas Dobrovodsky 68 16: , ,8 a 459 Peter Delincak 69 17: , ,7 a 413 Peter Delincak 70 (7. 4.) 15: a 384 Zdenko Bartos (8. 4.) 7: , ,9 e 313 Julius Koza 72 13: , ,5 e 399 Ales Kucera 73 (4. 8.) 15: a 546 Jozef Vilagi 74 (5. 8.) 15: a 555 Peter Veres 75 15: a 556 Tomas Dobrovodsky 76 16: , d 530 Stano Kaniansky 77 (6. 8.) 11: a 541 Jirı Silha 78 (6. 10.) 12: , ,9 c 436 Zuzana 85 Krisandova 79 ( ) 15: a 561 Juraj Toth Geographical position obtained from: a GPS Magellan SportTrack Pro (J. Toth), b Google Earth (J. Svoren), c GPS Garmin etrax Vista (P. Spurny), d Holux GPSport 245 (S. Kaniansky), e GPS Garmin n uvi (A. Kucera). photographing the meteorite and taking GPS coordinates of the location, the first meteorite served as a prototype for the next search and was shown to each participant, as most people had no previous experience in searching for meteorites. The second meteorite (No. 2, 81.3 g) was recovered just m from the first one. Both meteorites found that day had fresh fusion crust that covered 90% and % of the surface, respectively. The next day, March 21, the group from Astronomical Institute of SAS performed a search in a different strewn field area close to Alpinka resort, more than 4 km northeast of the first

6 858 J. Toth et al. finds. A group of eight participants found 11 meteorites from 2.75 g to g, with a range of fusion crust coverage from 90% to % of which 7 meteorites were fully crusted (Table 1). During March several expeditions were carried out with participants from the Comenius University, Astronomical Institute of SAS, Astronomical Institute of the Czech Academy of Sciences, and from public astronomical observatories. Altogether 61 meteorites were collected and cataloged and announced to the public during an official press conference on March 31, held in Stara Lesna. To protect the site, details on the geographical position of the strewn field were not released. Later, between March 28 and October 28, 2010, several expeditions were organized, which found additional 17 meteorites. A detailed description of expeditions, localities, meteorite characteristics, and participants can be found in a future publication. The total number of official finds is 78 with total mass of 4.3 kg. The range of the mass of the fragments spans from 0.57 g to g. Altogether, 34 participants took part in official expeditions, and the average number of finds was 2.6 fragments per person. The range of finds per person was from 0 to 9 with the average time for the find about 10 hours. The collection efficiency was estimated to be from 60 to 90%, depending mainly on visibility in the terrain. According to laws of the Slovak Republic, collecting of meteorites is allowed only for research by state or academic institutions of the Slovak Republic. Nevertheless, later we learned that a large number of meteorite fragments were found by private collectors from abroad and taken out of Slovakia. Only the largest one with the mass of 2.37 kg was delivered back to Comenius University in The positions and mass of majority of privately collected Kosice meteorites were announced to authors, which substantially helped to determine the strewn field area. There were an additional 140 meteorites added to the official finds of 78 meteorites, thus altogether 218 meteorites of 11.3 kg mass were found, representing about 0.32% of the calculated initial mass. A total of 6.7 kg are deposited in the Comenius University in Bratislava and in the Astronomical Institute of SAS in Stara Lesna. After most of the analyses are completed, samples of meteorites will be delivered to museums in Bratislava, Prague, Budapest, and Kosice. STREWN FIELD A first description of the strewn field and its comparison with predictions can be found in Borovicka et al. (2013). Here, we describe the strewn field based on Fig. 3. The distribution of recovered fragments (218 pieces) in the strewn field and the number of recovered fragments along the central line of the strewn field is depicted. The main fragments concentration is only about 2 km wide, placed on the main ridge between Vysny Klatov and Alpinka. the official finds of 78 meteorites and the additional 140 unofficial finds for which masses and recovery positions were available (Fig. 2). The strewn field is located about 5 km northwest of the city of Kosice, between the two villages of Vysny Klatov and Kavecany. The size of the strewn field is km, within the predicted strewn field calculated by Borovicka et al. (2013). About 90% of recovered meteorites occupied an area of km (Fig. 3). The whole strewn area consisted of low ridges and valleys with the altitudes range from 300 to 600 meters above sea level, but some slopes were steep. Most of the strewn field was covered by forest that was easy to be searched, but with a small area covered by dense bush. The rest of the strewn field area consists of meadows. Figures 4 and 5 indicate that the distribution of fragments does not follow expected distribution, which should place smaller fragments close to the end part of the fireball luminous trajectory on the southwest side, while the largest fragments should continue farther away from the terminal point to the northeast. We can confirm that the strewn field is much more complex and resembles different fragmentation phases and wind spread as described in Borovicka et al. (2013). Moreover, we would like to stress our own results from strewn field analyses, the individual fragments came from different internal parts (layers) of the original meteoroid body as showed by Povinec et al. (2015), and are not in a correlation with fragmentation sequence in the atmosphere and do not show any representational patterns in the strewn field. Surprisingly, fragments smaller than 10 g were found in a smaller strewn field area when compared to 10 g g fragments (Fig. 4). We expected that the range of fragments above 10 g is

7 Kosice meteorite fall 859 Fig. 4. The distribution of recovered fragments (218 pieces) in the strewn field (geographical longitude and latitude) versus their mass. The overall size of the strewn field for fragments smaller than 10 g is smaller by selection effect. The majority of fragments heavier than g follow the line from southwest to northeast (except two fragments on the west, and one fragment on the east). the most representative for actual strewn field description, as it is supported by the Borovicka et al. (2013) model of completeness of recovered fragments. The distribution of the largest fragments (> g) was quite different. Their spread perpendicular to the flight was small (three pieces), and the rest followed the line within about 220 m. However, the largest two fragments with masses over 2 kg were quite far from each other (about 1.4 km along the line), and represented two main concentrations of smaller fragments (Fig. 5). Independently, Gritsevich et al. (2014) also suggested the two different mass distributions of fragments. Moreover, these two largest fragments have different 60 Co activity values (Povinec et al. 2015), and they are from different parts of the parent meteoroid. Thus, the suggestion by Borovicka et al. (2013) that these fragments came from the same fragmentation event at 21.5 km, and from the same parent fragment, is not probable. We do not expect that the Kosice meteorite strewn field may contain any substantially larger unrecovered fragments (Fig. 6). METEORITE PROPERTIES Among the official 78 finds, there were 49 fragments (63%) that were completely covered by the fusion crust. The rest had fusion crust coverage from 40% to 95%, where lower percentage is placed in two locations (Fig. 8, No. 54, 55 and 57, 58). About 32% meteorite fragments showed no ablation features on the broken light face. The interior of the meteorites was light gray. The missing parts of meteorites were usually only a surface crust and estimated mass of these missing parts was a few grams or less. Probably their secondary fragmentation occurred in the atmosphere between the final ablation phase and hitting the ground. That is why we assume that the cause of this final fragmentation might be thermal stress. This is supported by the observation of several crack features of the remaining fusion crust on meteorites. Generally, the fusion crust was black, rough, and usually about mm thick. The fusion crust had different quality and thickness among individual meteorites, which suggested different ablation phases in particular fragments history. Some meteorites had only partial fusion crust which was very thin and glossier (Fig. 7, No. 67), and where the morphology of coarse meteorite interior was still present. This kind of fusion crust might be a result of later fragmentation and a gentle ablation phase in the lower atmosphere. Most of the meteorite fragments, even those found within 1 month of the fall, had rusty spots on broken faces (Fig. 7, No. 33, Fig. S1). The largest, 2.37 kg meteorite was a complete individual find. On the other hand, the second largest one, 2.17 kg (No. 55, Fig. S1), was covered by a thick fusion crust from 70%, while 20% was covered by thin glossy fusion crust, and 10% of the surface was free of any fusion crust. The 9 g fragment (No. 54, Fig. S1), which was found close to meteorite No. 55, was very probably the part of the main piece of No. 55. Similarly, meteorites No. 57 (51.94 g) and No. 58 (5.64 g) were found close to each other and they were two pieces of one meteorite

8 860 J. Toth et al. Fig. 5. The distribution of all fragments (218) in the strewn field in 3-D visualization. Two main concentrations of different masses around 2 kg fragments are visible. fragment, which fell down on a rocky terrain and broke up. Figure 8 shows the distribution of official finds with fusion crust coverage in percentage, where two main areas of less fusion crust coverage are circled. There were no substantially rocky terrains in that area, so we may conclude that these fragments came from a later fragmentation process after the ablation. Moreover, some parts of light faces of fragments without fusion crust have shown round edges and gentle ablation features. Meteorite No. 15 (3.03 g, Table 1) was the first one selected for mineralogical analysis. This meteorite was only partially covered by the fusion crust. It was cut into two parts and a thin section was made. It was classified as an ordinary chondrite H5 (Borovicka et al. 2013). Meteorite fragments, No. 20 (22.39 g) and No. 58 (5.64 g), were later selected for detailed mineralogical and chemical analyses, and the results can be found in Ozdın et al. (2015). Samples No. 35, 38, and 54 were also studied using LIBS (laser-induced breakdown spectroscopy) (Hornackova et al. 2014). Later, 67 meteorite fragments (the largest collection analyzed until now from one meteorite fall) were measured for their bulk and grain densities as well as for magnetic susceptibilities to search for any possible different types of meteorite within the Kosice. The average bulk density was g.cm 3 and the average grain density was g.cm 3. The porosities of meteorites varied from 4.2% to 16.1%. The mean value of the logarithm of the apparent magnetic susceptibilities was Am 2 kg 1 (Kohout et al. 2014), which was consistent with other ordinary chondrites. Fig. 6. Incremental distribution of recovered fragments (218) in logarithmic scale. Fragments smaller than 10 g are affected by selection recovery effect. The most representative part of the distribution is in the range 10 g. The heaviest fragments are far away from others in the mass range. The brecciated texture as well as S3 stage of shock metamorphism of the Kosice meteorite indicated a series of previous violent collisions in space. The central part of the asteroid Main Belt is the most populated region and is known for relatively frequent collisions among asteroids. The probable origin of the Kosice meteorite orbit is located in the central region of the belt as was dynamically shown by Borovicka et al. (2013). This kind of severe collisional history might be a source of the meteoroid weak structure as was observed in the atmosphere during the fragmentation phase. The Kosice meteoroid fragmented already at the height of 57 km under the dynamic pressure of only 0.09 MPa. The majority of the mass was released at the height of 39 km under the pressure of about 1 MPa following a series of later fragmentations (Borovicka et al. 2013). Its dynamic fragmentation behavior resembled other large meteoroids like Tagish Lake carbonaceous chondrite (Brown et al. 2002) or Almahata Sitta heterogenous meteoroid (Borovicka and Charvat 2009; Jenniskens et al. 2009). The Kosice ordinary chondrite was homogenous in physical parameters like magnetic susceptibility, bulk, and grain density. We conclude, however, the Kosice meteorite shared similar weak internal structure as other two above mentioned meteoroids having similar behavior in the atmosphere, and heavy fragmentations. The weak structure of the Kosice chondrite was different from other carbonaceous chondrites or brecciated polymict lithologies. On the other hand, some ordinary chondrites like Carancas (Borovicka and Spurny 2008) had very high strength

9 Kosice meteorite fall 861 Fig. 7. Three fragments (No. 1, 33, 67) with different type of the fusion crust and weathering of the interior. The glossy fusion crust of the fragment No. 67 is different from thick fusion crust of fragment No. 1 and 33. Fig. 8. The distribution of 78 official finds versus fusion crust coverage (%). Fragments in two areas (circled) have smaller percentage of fusion crust coverage of their surfaces, which represents secondary fragmentation after the ablation phase in the atmosphere. of about MPa, which prevented them from fragmenting in the atmosphere. It is clear that this is not applicable to the Kosice meteoroid, which has a weak internal structure after a rich collisional history. The comprehensive statistical study of recovered fragments of Kosice meteorite (Gritsevich et al. 2014) led to a possible conclusion that the original meteoroid was composed from two main different components, which should be the same meteorite type (H ordinary chondrite, Kohout et al. 2014), but different in physical properties leading to different mass distribution of fragments. This is very well represented by the strewn field distribution of fragments, as well as by fragmentation processes in the atmosphere. DISCUSSION The Kosice meteorite fall was an exceptional case in meteorite fall history as an instrumentally observed fall with a description of 218 fragments, defining in detail its strewn field. That allowed us to gather and characterize basic properties (mass, shape, fusion crust coverage, position) of individual fragments, and track their atmospheric fragmentation trajectories from a statistical point of view. According to our catalog (Table 1), we are able to pinpoint complex mineralogical, chemical, isotopic, and physical analyses of the specific fragment of the meteorite found in the strewn field. One can clearly see that complex forces,

10 862 J. Toth et al. which took place during fragmentation, are manifested in the strewn field distribution of fragments. The wind spread small fragments and mixed their distribution in the strewn field. On the other hand, bigger fragments followed a straight line for 220 m, and were not dispersed too much by fragmentation lateral forces or even by aerodynamic forces, except of several fragments found far in both sides of central line of the strewn field. Moreover, cosmogenic isotopes analyses (Povinec et al. 2015) showed that distribution of two largest fragments originating from different depth of parent meteoroid were also very well mixed in the strewn field and represented two distinct groups of smaller fragments. We concluded that found fragments were members of the same type of H5 ordinary chondrite meteorite with relatively uniform bulk and grain densities as well as magnetic susceptibilities at least of 67 inspected fragments, which suggested a homogenous meteorite type. However, the structural properties of fragments varied significantly as it was observed from early fragmentation phases under very low dynamic pressures as well as from statistical analyses of fragments mass distribution. The data presented in this paper will serve for future analyses of dark flight modeling of individual fragments. CONCLUSIONS The main results presented in this work may be summarized as follows: We collected 78 fragments of total mass of 4.3 kg during official expeditions organized by the Comenius University and the Slovak Academy of Sciences; We were able to collect information about position and mass of additional 140 fragments collected by individuals, where the largest one of 2.37 kg was returned to Slovakia; The predicted and actual strewn fields correlate well, and the majority of large meteorite fragments were recovered; We do not expect any substantially larger unrecovered fragments in the strewn field; The distribution of meteorite fragments in the strewn field does not correlate with the fragmentation sequence in the atmosphere; The majority of largest fragments (> g) were located within 220 m of the central line of the strewn field, which means that no dramatic lateral forces acted; There are two main concentrations of meteorite fragments around two more than 2 kg fragments, which are from two different parts of the original meteoroid; We conclude that the fusion crust lost during the dark flight was due to a thermal stress just after the ablation was stopped (the largest temperature gradient); The internal structure of the parent meteoroid was weak, and recovered number of small fragments and their distribution represents heavy fragmentation in the atmosphere. ACKNOWLEDGMENTS We thank all who participated in meteorite searches and successful finders, in particular Stanislav Kaniansky, Marcel Skreka, Miroslav Seben, Jozef Nedoroscik, Zuzana Mimovicova, Jaromır Petrzala, Tomas Dobrovodsky, Peter Delincak, and Zdenko Bartos. We also thank D. Heinlein, Z. Tyminski, J. Woreczko, and T. Gulon for information about nonofficial meteorite finds. This work was supported by GA CR grants No. P209/11/1382 and the Praemium Academiae of the AS CR, grants VEGA 1/225/14, APVV , and APVV Editorial Handling Dr. Donald Brownlee REFERENCES Borovicka J. and Charvat Z Meteosat observation of the atmospheric entry of 2008 TC 3 over Sudan and the associated dust cloud. Astronomy & Astrophysics 507: Borovicka J. and Kalenda P The Moravka meteorite fall: 4. Meteoroid dynamics and fragmentation in the atmosphere. Meteoritics & Planetary Science 38: Borovicka J. and Spurny P The Carancas meteorite impact Encounter with a monolithic meteoroid. Astronomy & Astrophysics 485:L1 L4. Borovicka J., Toth J., Igaz A., Spurny P., Kalenda P., Haloda J., Svoren J., Kornos L., Silber E., Brown P., and Husarik M The Kosice meteorite fall: Atmospheric trajectory, fragmentation, and orbit. Meteoritics & Planetary Science 48: doi: /maps Brown P. G., ReVelle D. O., Tagliaferri E., and Hildebrand A. R An entry model for the Tagish Lake fireball using seismic, satellite and infrasound records. Meteoritics & Planetary Science 37: Gritsevich M., Vinnikov V., Kohout T., Toth J., Peltoniemi J., Turchak L., and Virtanen J A comprehensive study of distribution laws for the fragments of Kosice meteorite. Meteoritics & Planetary Science 49(3): Hornackova M., Plavcan J., Rakovsky J., Porubcan V., Ozdın D., and Veis P Calibration-free laser induced breakdown spectroscopy as an alternative method for found meteorite fragments analysis. European Physical Journal Applied Physics 66: Jenniskens P., Shaddad M. H., Numan D., Elsir S., Kudoda A. M., Zolensky M. E., Le L., Robinson G. A., Friedrich J. M., Rumble D., Steele A., Chesley S. R., Fitzsimmons A., Duddy S., Hsieh H. H., Ramsay G., Brown P. G.,

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