The bolide of February 10, 2010: Observations in Hidalgo and Puebla, Mexico

Guadalupe Cordero^1*, Karina Cervantes–de la Cruz² and Eduardo Gómez²

¹ Departamento de Ciencias Espaciales Instituto de Geofísica Universidad Nacional Autónoma de México Ciudad Universitaria Delegación Coyoacán, 04510 México, D.F. Fax: +52 (55) 55 50 24 86 Tel. +52 (55) 56 22 41 13 (ext. 20) ^*Corresponding author: gcordero@geofisica.unam.mx

² Seminario Mexicano de Meteorítica Instituto de Geología Universidad Nacional Autónoma de México Ciudad Universitaria Delegación Coyoacán, 04510 México, D.F. Tel. +52 (55) 56 22 43 00 (ext. 105) e–mail: kecervan@yahoo.com.mx

Received: May 8, 2010 ]]> Accepted: September 28,2010
Published on line: December 17, 2010

Resumen

El 10 de febrero de 2010 los habitantes de algunas poblaciones cercanas a los límites entre los estados de Puebla e Hidalgo, México, escucharon un fuerte estallido sobre sus cabezas acompañado de tremores sísmicos y vibración en techos de lámina y vidrios. Algunas personas en Tulancingo, Hidalgo, localizado a unos 25 km de distancia de la zona, vieron un bólido y escucharon una explosión asociada a él aunque de mucho menor intensidad que el escuchado cerca del lugar de la explosión. Una de las posibles explicaciones dadas al evento fue que el fenómeno auditivo y visual se debió a la entrada de la basura espacial número 33006 proveniente del satélite COSMOS 2421. En este trabajo se analiza dicha posibilidad, se reportan los resultados de las entrevistas hechas a testigos y se evalúa la hipótesis alternativa de que el bólido pudo ser producido por la caída de un meteoroide.

Palabras clave: bólido, meteoro, escombros espaciales, México.

Abstract

On February 10th, 2010, the inhabitant population of some towns near the border between the States of Hidalgo and Puebla, Mexico, heard a strong blast overhead and felt seismic tremors and roof and windows vibration. At Tulancingo, Hidalgo, 25 km from the explosion zone, visual reports of a bolide and thunder–like sounds were described. A possible explanation may be related with re–entry of spatial debris number 33006 from satellite COSMOS 2421. We describe interviews with witnesses. An alternative hypothesis is a meteoritic origin of the bolide.

Key words: bolide, meteoroid, spatial debris, Mexico.

Introduction

Approximately 40,000 tons of interplanetary material falls to the Earth each year (Brownlee, 2001). The effect of these objects depends on their size, velocity, angle of entry, and strength. Meteoroids between 0.05 mm and 20 cm diameter may produce meteors (Ceplecha et al., 1998), whereas meteoroids between 1 m and 10 m can produce bolides (Shumilov et al., 2003) with energies of explosion of ~5 kt (Brown et al., 2002). Small asteroids, ~50–100 m of diameter, also produce bolides and usually explode in the air (Brown et al., 2002). Their energy may be ≥ 10 Mt as in the Tunguska event (Ben–Menahem, 1975; Martin, 1966).

The estimated frequency of collision of meteoroids with diameters greater than 1 m is between 35 and 159 per year, depending on the assessment method (Brown et al., 2002; Poveda et al., 1999). This means that we would expect that one bolide occurs every 2 to 10 days on some place on Earth; however, they are not always observed because they fall near inhabited sites or weather conditions do not enable sightings.

When a bolide explodes in the atmosphere, the atmospheric shock wave generated by the explosion may produce seismic waves that can be detected at seismic stations, as for the events of Hawera, New Zealand in 1999 (Manville et al., 2004), and Bala, UK in 1974 (Musson, 2006). Occasionally, the explosion produces infrasonic signals recorded by microbarographs, as in the case of Vitim in 2002 (Shumilov et al., 2003).

The sound of the explosion may cause panic, as for the Curuça River event on August 13^th, 1930 (L'Osservatore Romano, 1931; Bailey, 1995). The October 8th, 2009 fireball in Indonesia was attributed to an object 10 meters in diameter with an energy of about 50 kt (http://neo.jpl.nasa.gov/news/news165.html).

Observations

On February 10th, 2010, around the 15:50 local time, a strong explosion was heard in the municipality's counties of Tulancingo (Hidalgo) and Ahuazotepec (Puebla). Most reports came from the localities of El Durazno, and Las Puentes (Hidalgo) and Ahuazotepec (Puebla), in east central Mexico (Fig. 1). The sound was related to a sudden strong burst, but no sightings were reported because of the fog. However, witnesses reported a rumble similar to that of a heavy truck. No objects did fall but the windows vibrated. Many people thought that an explosion had taken place in the nearby gas pipeline or in the petrochemical plant.

In Tulancingo, Hidalgo, some 25 km west from the estimated place of the explosion, a bolide was seen and a dull sound was heard. Witnesses thought that an airplane had crashed.

Several other versions of the event emerged. Rumors included an impact of a meteorite causing a bridge to collapse, or producing a 30 m impact crater. UFO sightings were also reported.

The media in the area compiled several testimonies from the inhabitants. Many people went to the area looking for remains of an air crash, the explosion of pipeline, spatial debris, a meteorite or an extraterrestrial spaceship.

Spatial Debris

The Mexican Space Agency AEXA suggested that the bolide might have been produced by the reentry of a fragment of COSMOS 2421, debris numbered 33006 (Herrera–Cortés, 2010).

We performed an information search about this debris or any other that could have fallen in Mexico on February 10th, 2010. Celestrak (http://celestrak.com/) and Space Track (http://www.space–track.org/perl/decay_query.pl) reported that debris 33006 from COSMOS 2421 had fallen on February 12th, 2010 not February 10th. On the other hand, Space Track listed two events in February from COSMOS 2421, the 33755 on February 6th and the 33006 on February 12th. On this last date there was also debris 30808 from the Chinese satellite Fengyun 1C, and debris 29455 from satellite SL–12 of the Commonwealth of Independent States. On February 10th only one fall was found, debris number 34251 from the tank Breeze–M. No location was reported for this event.

The Orbital Debris Quarterly News (http://www.orbitaldebris.jsc.nasa.gov/newsletter.html), a publication of the NASA Orbital Debris Program Office, publishes news, statistics, and valuable material on spatial debris. In issue 2, volume 14 published in April 2010, no mention is made of an event on February 10th in Mexico. As debris 34251 was not expected to fall in Mexico, the bolide of 10 February may have been caused by a meteoroid.

Methodology

Two weeks after the event, we went to the area of the explosion to interview possible witnesses of the event. Over a period of 4 months, after the event we returned to the area 12 times. Even though more than 80% of the interviewed people heard the sonic boom and/or perceived windows or roof vibration, very few saw the bolide. We required eyewitnesses to return to the location where they observed the fireball and asked them to point at the initial and final points of the trajectory that they saw. With some object in the horizon as reference, we measured the azimuth and angle over the local horizon for each point using a BRUNTON compass (Trigo–Rodríguez, et al., 2006). Geographic coordinates were obtained with GPS.

To find the intersection, we used a Wulff (equal–angle) stereo net and we plotted the pair of lines for every eyewitness as a pair of points on the stereo net. Then we rotated the stereo net until both points fell on a great circle. This was the plane containing both lines. For each eyewitness, individual planes and poles of each plane were obtained. The poles of the planes were plotted using the Dips 5.041 program (Fig. 3). The poles were located in four regions of the stereo net (I to IV on Fig. 3); to obtain average planes whose intersections yielded the possible trajectory of the bolide. The solution was not unique because of measurement errors and because witnesses failed to remember the exact points where they saw the bolide.

Assessment of the Trajectory

It is important to know the path of a bolide in the atmosphere as it allows one to determine the orbit and associate it with NEOs or Main Belt asteroids. It also helps delimiting the area where a meteorite search can be performed. A good way to carry out this search is by means of meteor networks, such as the Spanish Meteor Network (Madiedo et al., 2009), which has been successful in determining the orbits of some bolides and the area where meteorites have been recovered (Trigo–Rodríguez et al., 2006). For the event of 10 February 2010, nor videos nor photographs or sound records are available.

Data

Over one hundred people were interviewed in thirteen towns (Table 1), but only twelve saw the event. The twelve witnesses showed us the place where the fireball was sighted. We required them to return to the place where they observed the fireball and to point out the initial and final points of the segment of the trajectory that they saw. With some object in the horizon as a reference, we took the azimuth and the angle over the local horizon for each point. The result is shown in Table 2 and the Fig. 2. Fourth column in Table 2 gives the azimuth (from the North through East) and the fifth column shows the angular elevation of the object as referred to the local horizon. There are two rows for each witness, the first for the initial point of the observed path and the second for the final point.

The luminosity of a bolide depends on the mass loss rate of the meteoroid (Ceplecha et al., 1998; Hills and Goda, 1993). Extinction occurs when the ablation is over, that is, when the bolide slows down to ~3 km s^–1 (Passey and Melosh, 1980; Ceplecha et al., 1998; Trigo–Rodríguez et al., 2006). Thus the observed path corresponds to the luminous part of the trajectory in the atmosphere.

According to witness 3, the bolide flared up two or three times during the time of observation (~3). Each flare–up represents a discrete fragmentation event (Ceplecha and ReVelle, 2005; Trigo–Rodríguez et al., 2006). Thus the bolide had two or three minor fragmentations before it was extinguished. Finally, the meteoroid exploded and the report was heard by the inhabitants of localities around El Durazno.

Witnesses 6 to 11 were in a football field in Tepaltzingo (Fig 2) when they saw the bolide. They describe the bolide as a fire ball whose apparent magnitude range was between 6 and the full Moon (–12). They commented that the object sparkled like burning wood and looked blue in front, red in the middle part and yellow–orange at the tail. They heard a sound like a sonic boom approximately 7 seconds after they lost sight of the bolide behind a nearby hill.

Witness 12 was in a prickly pear field in San Felipe. He described the bolide as an object similar to the size of a compact car.

Trajectory

Using the stereographic method described in methodology section 4, we obtained the planes and the poles of these planes from the data provided by each eyewitness. Plotting the poles, we found that they could be grouped into four sets of points labeled with roman numerals in Fig. 3. For each set of points we obtained an average pole and plotted the perpendicular plane to it (curves I to IV in Fig. 3). The resulted planes are defined by a deep (inclination with respect horizontal) and a strike (direction perpendicular to deep) (Table 3). The intersection of these planes must be the trajectory of the bolide.

Considering the points of intersection between the most confident data (curves I, II and III), we obtained several possible trajectories (Table 4). The intersection between planes I and III was rejected, because the bolide would have traveled in a direction opposite to the one which was actually seen. The intersection between planes II and III yielded an East–West direction to the trajectory; this result is more reasonable but a West–East direction does not represent all the data. The trajectory obtained from the intersection between planes I and II defines better the flight of the bolide. The azimuth of the trajectory is between 55º and 90º, represented by two lines through the orange star in Fig. 2. This star points to the location where the sound of the sonic boom was the strongest within the area enclosed by triangles where the sound was very strong.

According to witnesses in Ahuazotepec, El Durazno and Las Puentes (Table 1), a tremor, similar to the one produced by the passing of a heavy truck was associated with the explosion. In El Durazno, water in ponds overflowed, as in an earthquake. According to this, people felt a seism of intensity I to IV on the Mercalli scale (Lowrie, 1997). No earthquake was recorded at the seismological stations near the area. There were no microbarographs in the area.

Future Work

More field work in needed to constrain the trajectory of the bolide in order to constrain the area where to look for meteorites. Meanwhile, it is probable that a meteorite or meteorites could be found in the mountains around El Durazno, though this is not an easy task.

A meteor network in Mexico will require documenting the incidence of meteoroids and small bodies.

Conclusions

This event caused fear among the inhabitants of Hidalgo and Puebla and was reported in the media. Civil protection and military agencies were involved in the search. It is important to study this kind of events in order to inform and to calm people. The civil protection departments of both states gave us all the information that they compiled.

Unfortunately, there were no seismic, barographic, photographic or sonic records that we could use to define the trajectory of the bolide. It is important to have a bolide network.

From the data of twelve eyewitnesses, we obtained a rough estimation of the trajectory of the bolide. The azimuth falls between 55º and 90º with an angle to the horizontal of between 16º and 47º.

Acknowledgments

The authors would like to acknowledge Jesús García Avila and José Luis Lastiri García, heads of the civil protection and fire departments of Tulancingo (Hidalgo) and Zacatlán, (Puebla) and their staffs. The assistance of Lic. Jorge Márquez Alvarado and C. Raymundo Olvera Muñóz, municipal presidents of these localities, and inhabitants of these sites, is much appreciated. Without their cooperation, interest, and kindness, it would not have been possible to do this work. We thank the support of the Institute of Geophysics, UNAM. We thank Jose Luis García Martínez and Gilberto Arreguín Molina for their useful comments to this work.

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