Several bolides studied by the Spanish Fireball
Network: Villalbeto de la Peña and other
2003-2006 events
J. M. Trigo-Rodrı́guez1,2 , J. Llorca2,3 , J.L. Ortiz4 , J.A. Docobo5 and A. J.
Castro-Tirado2
1. Institute of Space Sciences (CSIC), Campus UAB, Facultat de Ciencies, Torre
C-5, parells, 2a planta. 08193 Bellaterra (Barcelona), SPAIN. E-mail:
trigo@ieec.uab.es
2. Institut d´ Estudis Espacials de Catalunya (IEEC), Gran Capita 2-4, Ed.
Nexus, 08034 Barcelona, SPAIN.
3. Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya,
Diagonal 647, 08028 Barcelona, Spain.
4. Instituto de Astrofisica de Andalucia (IAA-CSIC), PO Box 3004, 18080
Granada, Spain.
5. Observatorio Astronomico Ramon Maria Aller. Universidade Santiago de
Compostela, Spain
Summary. Meteorite falls in the Earth are announced by very bright bolides that
are able to survive ablation and produce light well below 25 km height. In a few
seconds meter-sized objects penetrate from the outer space to the lower atmosphere
at ultrasonic speeds. We are currently setting up an all-sky CCD fireball network in
order to get accurate trajectory and orbital data of large bolides appeared over the
Iberian Peninsula. We describe the current status of such a project and the brightest
fireball events recorded during the first years of operation. Particularly, we describe
the study by our team of the Jan. 4, 2004 daylight superbolide that allowed the first
meteorite recovery (the L6 ordinary chondrite Villalbeto de la Peña) in 56 years.
1 Introduction
By recording bright bolides from different stations in the Earths surface is
possible to get valuable data on the origin and physical properties of large
meteoroids produced by fragments of comets and asteroids. These luminous
events are produced by the ablation of centimeter-sized particles that encounter the Earth at high velocities (typically in the range of 11 to 72 km/s).
Beyond the showiness of a fireball, the study of the luminous path from several
locations allows the determination of its atmospheric trajectory. Additionally,
by using a rotating shutter, the entry velocity of the fireball can be determined, and from this is possible to reconstruct its heliocentric orbit. Fireballs
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produced by cm-size pebbles usually disintegrate completely as fine dust after
producing beautiful natural fireworks. On the other hand, meter-sized bodies
enter into the atmosphere producing spectacular events that are called superbolides, but not all are able to survive the violent atmospheric interaction.
Multiple station recording and subsequent trajectory reconstruction provide
clues to decipher when a meteorite recovery is likely. Despite their large size,
only if the meteoroid trajectory slope, entry velocity and strength [1] are propitious, appreciable fragments of the original body can survive atmospheric
interaction, reaching the ground as meteorites. In the present text we will
focus on these large events because one of our main goals is the recovery of
meteorites on the basis of the previous determination of their atmospheric
trajectories by multiple station recording of their respective bolides. We hope
that as consequence of our continuous all-sky monitoring effort will be possible to recover meteorites in regions of the Iberian Peninsula and northern
Africa in the future. Both locations are very suitable for meteorite recovery
and, consequently, the appearance of meteorite-dropping events deserve to be
systematically studied.
2 Current status and instrumentation
We are currently setting up an all-sky CCD automatic system for detecting
meteors and fireballs called SPanish Meteor Network (SPMN). By the end of
2006 the first four stations in operation are located in Andalusia and Catalonia (see Table 1). The cameras have been developed following the BOOTES-1
prototype installed at the El Arenosillo Observatory in 2002. Such prototype is
based on a CCD detector of 4096x4096 pixels with a fish-eye lens that provides
an all-sky image with enough resolution to make accurate astrometric measurements. In fact, the stellar limiting magnitude of the images is +10 in the
zenith, and +8 below 65 of zenithal angle, while the typical meteor limiting
magnitude is +2/+3 depending of the geocentric velocity, meteor geometry
with the radiant, and lens vignetting [2]. Consequently, the images obtained
by this instrument provide enough comparison stars to make astrometric measurements of bright meteors and fireballs with an accuracy of 1.5 arcminutes
[2]. Recently we have developed an inner rotating shutter that obturates the
image 50 times/s in order to measure the velocity of the meteors.
3 Large bolides studied between 2003 and 2006
We include here several events studied by our network (see Table 2). In the
first part of this section we will describe the bolide better studied until date,
this one associated with the fall of Villalbeto de la Peña meteorite. In a second
part, we describe other four cases studied or currently under study.
Several bolides studied by the Spanish Fireball Network
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Table 1. Current all-sky stations of the Spanish Fireball Network
Station
Longitude
La Mayora (Mlaga)
El Arenosillo (Huelva)
Montsec (Lleida)
Montseny (Girona)
04
06
00
02
02
43
43
31
40”
58”
46”
14”
Latitude
W
W
E
E
36
37
42
41
45
06
03
43
Altitude (m)
35” N 60
16” N 40
05” N 1570
17” 300
Table 2. Large fireballs recorded by the SPMN
Name
Date
Time
(UTC)
Nador
Villalbeto de la Peña
Ourense-Guimaraes
Eivissa
Ceuta
Almeria
Jan. 27, 2003
Jan. 4, 2004
Mar. 1, 2005
Apr. 13, 2005
Jun. 30, 2005
Jul. 30, 2005
Hour
16h46m45s
15h13m
6h14m
2h21m22s
0h03m15s
Ending
Absolute height
Magnitude (km) Notes
-16
-18
-15
-12
-15
-13
25
22.2
22
> 30
60
25
Likely meteorite survival
Meteorites recovered
Likely meteorite survival
Unlikely survival
No survival
Likely meteorite survival
3.1 Villalbeto de la Peña superbolide
Villalbeto de la Peña bolide reached -18 absolute magnitude, being detected
from space by DoD satellites. Few days after the fall several meteorites were
found, and an extensive meteorite recovery campaign was organized by our
team. Such event was perfectly visible in the afternoon sky, and it is not
strange that tens of eyewitnesses reported the fireball appearance to the
SPMN. However, the most valuable data of this daylight bolide were obtained
by chance from a video and three pictures taken by amateurs (see Fig. 1).
Paragraph Heading
Some pictures were taken showing buildings or countryside features that were
used for astrometric calibration [5]. After the reduction procedure the atmospheric trajectory and the velocity were computed from the study of the
meteoroid flight in the video frames and pictures. The entry velocity was
computed at the top of the atmosphere because the video only provided the
velocity in the lower part of the trajectory. From the initial velocity the ninth
heliocentric orbit of a meteorite in the solar system was obtained [5]. The orbit
of this body indicates its origin in the main asteroid belt (Fig. 6), just like in
the eight previous cases of meteorites with well determined orbits. ¿From the
study of cosmogenic noble gases an average cosmic-ray exposure age 48+-5
Ma was obtained. This is the period of time that the meteoroid spent as a
meter-sized object since was released from its parent asteroid. Despite that
the origin in the main belt is common for the previously determined meteorite
References
[3]
[4, 5]
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Fig. 1. Casual picture of Villalbeto de la Peña bolide taken by Mara M. Robles from
Santa Columba de Curueo (Len). After the meteorite break up, several fragments
flew separately behind the main body.
orbits, Villalbeto de la Peña orbital elements have peculiarities that deserve
additional discussion. For example, as distinguished from the previous eight
meteorites with determined heliocentric orbit, Villalbeto de la Peña progenitor meteoroid was lying exactly in the ecliptic plane. This fact makes possible
to invoke other delivery mechanisms for explaining the arrival of this body
to the Earth. An example is the Outer Main Belt (OMB) source that, by using the Bottke et al. (2002) approach, shows an unusual high probability for
being the source of this meteorite inside the uncertainty range in the orbital
elements. However, other dynamic mechanisms are also likely like e.g. the 3:1
and Nu6 Jovian resonances, or the Mars-crossing region. Unfortunately the
uncertainty in the orbital elements makes impossible to decide among these
four good candidates [5].
3.2 Other recent cases under study
The extraordinary efficiency of our all sky CCD system was exemplified by the
detection of the Jan. 27 2003 bolide that overflew Algeria and Morocco, and
just had its ending over Nador [5]. The event was recorded from El Arenosillo
station located in Huelva province more than 400 km away, and also reported
by visual observers in Mlaga, Murcia and Granada. Unfortunately the trajectory accuracy was limited by the absence of a second image from a second
station. This early result, just during the first months of operation of our first
Several bolides studied by the Spanish Fireball Network
5
prototype motivated us to create a second station in Andalusia in La Mayora
(Mlaga). A couple of years later, on Jun. 30 2005, we got our first bolide from
both stations appeared over the coast of Ceuta. Such event had absolute magnitude -15, but the cometary nature of the meteoroid was exemplified by the
altitude of the ending light. We cannot expect meteorite survival for this kind
of events because the meteoroids are very fragile and become fine dust after
ablation. In fact cometary meteoroids typically produce Type II or III bolides
[6] that are unable to survive atmospheric interaction and exhibit ending flares
(see Fig. 2). However, there is growing evidence that some comets can produce
higher strength materials capable to survive ablation under favourable impact
geometry and low entry velocity.
Fig. 2. The Ceuta bolide as seen from La Mayora all-sky station
Paragraph Heading
Unfortunately, not all bolides can be imaged. Daylight events cannot be imaged by our CCD cameras, and only in very favourable cases are videotaped or
photographed by casual eyewitnesses as occurred in the Villalbeto de la Peña
case. A good example of this was the Ourense-Guimaraes event observed at
midday of Mar. 1, 2005. In this case, we got more than 20 visual reports of
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the bolide trajectory from Galicia and the North of Portugal in order to reconstruct the trajectory for determining the likely recovery area [7]. In order
to get a fireball trajectory with reasonable accuracy is necessary to interview
people in the same place where they observed the event. Precise theodolite
measurements are also required although eyewithnesses reports are affected
by the observer’s perception and memory. As a consequence, a statistically
high number of data from a well-spaced area are required in order to get valuable data. Additionally, the different apparent trajectories can be compared
and weighted as a function of their deviation from an averaged trajectory. In
this way, low-quality observations can be removed and the trajectory significantly improved in progressive steps. However, despite of all this effort the
accuracy of the trajectory determination is much lower than can be obtained
from fireball recording.
4 Conclusions
In order to increase the number of tracked fireball events, and the subsequent
meteorite recovered cases with information on their orbital elements, the development of new networks around the world is required. We still are far to
understand several key points on minor bodies like e.g. the dynamic processes
capable to deliver meteorites from the main belt to the Earth, the possible
origin of meteorites in evolved (processed) comets, or the likely existence of
streams of meter-sized meteoroids (capable to produce meteorites) in collision
route with the Earth. Recent application of CCD and video cameras to meteor and fireball detection allows to get observational evidence of processes
that are difficult to be studied by other conventional techniques [8, 9]. Consequently, we encourage other teams to use the new available technology for
increasing the meteor and fireball monitoring all around the world.
References
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95, 553 (2005)
3. Trigo-Rodrguez J.M., A.J. Castro-Tirado, J. Llorca et al. WGN Int. Met. Org.
J. 31, 49 (2003).
4. Llorca J., J.M. Trigo-Rodrguez, J.L. Ortiz et al. Meteorit. & Planet. Sci. 40,
795 (2005)
5. Trigo-Rodrı́guez J.M., J. Borovicka, P. Spurny et al. Meteorit. & Planet. Sci.
41, 505 (2006).
6. Ceplecha, Z., J. Borovicka, W. Graham Elford et al. Space Sci. Rev. 84, 327
(2006).
7. Docobo J.A., J. M. Trigo-Rodrguez, J. Borovicka et al. In preparation.
8. Spurny P., H. Betlem, K. Jobse et al. Meteorit. & Planet. Sci. 35, 1109 (2000)
Several bolides studied by the Spanish Fireball Network
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9. Trigo-Rodrguez J.M., A.J. Castro-Tirado, J. M Madiedo et al. IAU Circ. CBET
698 (2006)