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The Traspena meteorite fell on 2021 January 18 about 20 km south-east of the city of Lugo (Galiza, Spain), shortly after a huge and bright fireball crossed the sky for 4.84 s. Astrometric measurements obtained from the fireball cameras of the Universidade de Santiago de Compostela (USC) as well as from many casual videos were used to determine the atmospheric trajectory of this meteoroid which penetrated the atmosphere and generated sound waves that were detected at three seismic stations. The original meteoroid had a diameter of about 1.15 m and a mass around 2620 kg. It impacted the Earth’s atmosphere with a steep entry angle of about 76 . ◦7 from a height of 75.10 km until fading away at 15.75 km with a velocity of 2.38 km s −1 . Before the impact, this small asteroid was orbiting the Sun with a semimajor axis of 1.125 au, a moderate eccentricity of 0.386, and a low inclination of 4 . ◦55. A weak evidence of dynamic link with the PHA (Potential Hazardous Asteroid) Minos was investigated. During the atmospheric entry, two major fragmentation events occurred between heights of 35 and 29 km at aerodynamic pressures between 1 and 5 MPa. The strewn field was computed after calculating the individual dark flights of the main body along with two smaller fragments. For- tunately, 2 month after the superbolide, a 527-g meteorite was found. It was examined using several geochemical and petrographic analyses which allowed us to classify it as a moderately shocked (S3) L5 ordinary chondrite with a bulk density of 3.25 g cm −3 ., This paper was supported by the Xunta de Galicia (Spain) under the ED431B 2020/38 grant.

Anghel, S., et al., The increase in detector sensitivity and availability in the past three decades has allowed us to derive knowledge of the meteoroid flux and impact energy into the Earth's atmosphere. We present the multi-instrument detected 2018 December 22 fireball over Western Pyrenees, and compare several techniques aiming to obtain a reliable method to be used when measuring impacts of similar scale. From trajectory data alone, we found a bulk density of 3.5 g cm-3 to be the most likely value for the Pyrenean meteoroid. This allowed to further constrain the dynamic mass, which translated into a kinetic energy of 1 ton TNT (4.184 × 109 J). For the second energy derivation, via the fireball's corrected optical radiation, we obtained a more accurate empirical relation measuring well-studied bolides. The result approximates to 1.1 ton TNT, which is notably close to the nominal dynamic result, and agrees with the lower margin of the seismic-based energy estimation, yet way lower than the infrasound estimate. Based on the relation derived in this study, we consider the nominal estimate from both the dynamic and photometric methods to be the most accurate value of deposited energy (1 ton TNT). We show that the combination of these two methods can be used to infer the meteoroid density. Among the methods presented in this paper, we found that the optical energy is the most reliable predictor of impact energy near the ton TNT-scale., S. Anghel and D. A. Nedelcu were supported by a grant of the Romanian Ministry of Research and Innovation, CCCDI - UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0226/16PCCDI/2018, within PNCDI III. EP-A and JMT-R acknowledge funding from PGC2018-097374-B-I00 (MCI-AEI-FEDER, EU). M. Birlan work was partly supported by SEEING-IEA CNRS program. R. Hueso and A. Sánchez-Lavega were supported by Diputación Foral de Bizkaia and Gobierto Vasco IT1366-19.

Meteor physics can provide new clues about the size, structure, and density of cometary disintegration products, establishing a bridge between different research fields. From meteor magnitude data we have estimated the mass distribution of meteoroids from different cometary streams by using the relation between the luminosity and the mass obtained by Verniani. These mass distributions are in the range observed for dust particles released from comets 1P/Halley and 81P/Wild 2 as measured from spacecraft. From the derived mass distributions, we have integrated the incoming mass for the most significant meteor showers. By comparing the mass of the collected interplanetary dust particles (IDPs) with that derived for cometary meteoroids a gap of several orders of magnitude is encountered. The largest examples of fluffy particles are clusters of IDPs no larger than 100 μm in size (or 5 × 10–7 g in mass) while the largest cometary meteoroids are centimeter-sized objects. Such gaps can be explained by the fragmentation in the atmosphere of the original cometary particles. As an application of the mass distribution computations we describe the significance of the disruption of fragile comets in close approaches to Earth as a more efficient (and probably more frequent) way to deliver volatiles than direct impacts. We finally apply our model to quantify the flux of meteoroids from different meteoroid streams, and to describe the main physical processes contributing to the progressive decay of cometary meteoroids in the interplanetary medium., JMTR acknowledges financial support by the research project(PGC2018 097374-B-I00, funded by FEDER/Ministerio de Ciencia e Innovación – Agencia Estatal de Investigación. JB acknowledges the continuing support by the Deutsche Forschungsgemeinschaft and the Deutsches Zentrum für Luft- und Raumfahrt.

Statler et al., NASA’s Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ∼10% and characterization of the Didymos binary system. But DART is a single experiment; how could these results be used in a future planetary defense necessity involving a different asteroid? We examine what aspects of Dimorphos’s response to kinetic impact will be constrained by DART results; how these constraints will help refine knowledge of the physical properties of asteroidal materials and predictive power of impact simulations; what information about a potential Earth impactor could be acquired before a deflection effort; and how design of a deflection mission should be informed by this understanding. We generalize the momentum enhancement factor β, showing that a particular direction-specific β will be directly determined by the DART results, and that a related direction-specific β is a figure of merit for a kinetic impact mission. The DART β determination constrains the ejecta momentum vector, which, with hydrodynamic simulations, constrains the physical properties of Dimorphos’s near-surface. In a hypothetical planetary defense exigency, extrapolating these constraints to a newly discovered asteroid will require Earth-based observations and benefit from in situ reconnaissance. We show representative predictions for momentum transfer based on different levels of reconnaissance and discuss strategic targeting to optimize the deflection and reduce the risk of a counterproductive deflection in the wrong direction., This work was supported in part by the DART mission, NASA contract No. 80MSFC20D0004 to JHU/APL. Some of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). S.C. acknowledges funding through the Crosby Fellowship of the Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology. E.D., S.I., A.L., M.P., A.R., and P.T. are grateful to the Italian Space Agency (ASI) for financial support through agreement No. 2019-31-HH.0 in the context of ASI’s LICIACube mission, and agreement No. 2022-8-HH.0 for ESA’s Hera mission. R.L. appreciates the funding from the European Union’s Horizon 2020 research and innovation program, grant agreement No. 870377 (project NEO-MAPP). P.M. acknowledges funding support from the French space agency CNES, ESA and the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP). R.M. acknowledges support from a NASA Space Technology Graduate Research Opportunities (NSTGRO) Award (80NSSC22K1173). R.N. acknowledges support from NASA/FINESST (NNH20ZDA001N). J.O. and I.H. were supported by the Spanish State Research Agency (AEI) project No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu”—Centro de Astrobiología (CSIC-INTA). They are also grateful for all logistical support provided by Instituto Nacional de Técnica Aeroespacial (INTA). S.R.S. acknowledges support from the DART Participating Scientist Program, grant No. 80NSSC22K0318. J.M.T.R. was funded by FEDER/Ministerio de Ciencia e Innovación—Agencia Estatal de Investigación of Spain (grant No. PGC2018-097374-B-I00).

The Double Asteroid Redirection Test (DART) is the first planetary defense test mission. It will demonstrate the kinetic impactor technique by intentionally colliding the DART spacecraft with the near-Earth asteroid Dimorphos. The main DART spacecraft is accompanied by the Italian Space Agency Light Italian CubeSat for Imaging of Asteroids (LICIACube). Shape modeling efforts will estimate the volume of Dimorphos and constrain the nature of the impact site. The DART mission uses stereophotoclinometry (SPC) as its primary shape modeling technique. DART is essentially a worst-case scenario for any image-based shape modeling approach because images taken by the camera on board the DART spacecraft, called the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), possess little stereo and no lighting variation; they simply zoom in on the asteroid. LICIACube images add some stereo, but the images are substantially lower in resolution than the DRACO images. Despite the far-from-optimal imaging conditions, our tests indicate that we can identify the impact site to an accuracy and precision better than 10% the size of the spacecraft core, estimate the volume of Dimorphos to better than 25%, and measure tilts at the impact site over the scale of the spacecraft with an accuracy better than 7°. In short, we will know with excellent accuracy where the DART spacecraft hit, with reasonable knowledge of local tilt, and determine the volume well enough that uncertainties in the density of Dimorphos will be comparable to or dominate the uncertainty in the estimated mass. The tests reported here demonstrate that SPC is a robust technique for shape modeling, even with suboptimal images., This work was supported by the DART mission under NASA Contract 80MSFC20D0004. This work was supported by the Italian Space Agency (ASI) within the LICIACube project (ASI-INAF agreement AC n. 2019-31-HH.0). This work used the Small Body Mapping Tool (sbmt.jhuapl.edu). JMTR is funded by FEDER, Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación of Spain.

On February 16, 2021, an artificial object moving slowly over the Mediterranean was recorded by the Spanish Meteor Network (SPMN). Based on astrometric measurements, we identified this event as the reentry engine burn of a SpaceX Falcon 9 launch vehicle’s upper stage. To study this event in detail, we adapted the plane intersection method for near-straight meteoroid trajectories to analyze the slow and curved orbits associated with artificial objects. To corroborate our results, we approximated the orbital elements of the upper stage using four pieces of “debris” cataloged by the U.S. Government’s Combined Space Operations Center. Based on these calculations, we also estimated the possible deorbit hazard zone using the MSISE90 model atmosphere. We provide guidance regarding the interference that these artificial bolides may generate in fireball studies. Additionally, because artificial bolides will likely become more frequent in the future, we point out the new role that ground-based detection networks can play in the monitoring of potentially hazardous artificial objects in near-Earth space and in determining the strewn fields of artificial space debris. [Figure not available: see fulltext.], This research was supported by the research project (Grant No. PGC2018-097374-B-I00, PI: JMT-R), which is funded by FEDER/Ministerio de Ciencia e Innovación–Agencia Estatal de Investigación. This project has also received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (Grant No. 865657) for the project “Quantum Chemistry on Interstellar Grains” (QUANTUMGRAIN).

The petrology and mineralogy of shock melt veins in the L6 ordinary chondrite host of Villalbeto de la Peña, a highly shocked, L chondrite polymict breccia, have been investigated in detail using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and electron probe microanalysis. Entrained olivine, enstatite, diopside, and plagioclase are transformed into ringwoodite, low-Ca majorite, high-Ca majorite, and an assemblage of jadeite-lingunite, respectively, in several shock melt veins and pockets. We have focused on the shock behavior of diopside in a particularly large shock melt vein (10 mm long and up to 4 mm wide) in order to provide additional insights into its high-pressure polymorphic phase transformation mechanisms. We report the first evidence of diopside undergoing shock-induced melting, and the occurrence of natural Ca-majorite formed by solid-state transformation from diopside. Magnesiowüstite has also been found as veins injected into diopside in the form of nanocrystalline grains that crystallized from a melt and also occurs interstitially between majorite-pyrope grains in the melt-vein matrix. In addition, we have observed compositional zoning in majorite-pyrope grains in the matrix of the shock-melt vein, which has not been described previously in any shocked meteorite. Collectively, all these different lines of evidence are suggestive of a major shock event with high cooling rates. The minimum peak shock conditions are difficult to constrain, because of the uncertainties in applying experimentally determined high-pressure phase equilibria to complex natural systems. However, our results suggest that conditions between 16 and 28 GPa and 2000–2200 °C were reached.

Carbonaceous chondrite meteorites are so far the only available samples representing carbon-rich asteroids and in order to allow future comparison with samples returned by missions such as Hayabusa 2 and OSIRIS-Rex, it is important to understand their physical properties. Future characterization of asteroid primitive classes, some of them targeted by sample-return missions, requires a better understanding of their mineralogy, the consequences of the exposure to space weathering, and how both affect the reflectance behaviour of these objects. In this paper, the reflectance spectra of two chemically related carbonaceous chondrites groups, precisely the Vigrano (CVs) and Karoonda (CKs), are measured and compared. The available sample suite includes polished sections exhibiting different petrologic types: from 3 (very low degree of thermal metamorphism) to 5 (high degree of thermal metamorphism). We found that the reflective properties and the comparison with the Cg asteroid reflectance class point towards a common chondritic reservoir from which the CV-CK asteroids collisionally evolved. In that scenario, the CV and CK chondrites could be originated from 221 Eos asteroid family, but because of its collisional disruption, both chondrite groups evolved separately, experiencing different stages of thermal metamorphism, annealing, and space weathering., This research has been funded by the research project (PGC2018-097374-B-I00, P.I.: JMT-R), funded by FEDER/Ministerio de Ciencia e Innovacion – Agencia Estatal de Investigación. ST is hired in the framework of that research project

Drolshagen, E., et al., [Context] In meteor physics, the luminous efficiency τ is used to convert the meteor's magnitude to the corresponding meteoroid's mass. However, a lack of sufficiently accurate verification methods or adequate laboratory tests mean that discussions around this parameter are a subject of controversy. [Aims] In this work, we aim to use meteor data obtained by the Fireball Recovery and InterPlanetary Observation to calculate the luminous efficiencies of the recorded meteors. We also show the limitations of the methods presented herein. [Methods] Deceleration-based formulas were used to calculate the masses of the pre-atmospheric meteoroids. These can in turn be compared to the meteor brightnesses to assess the luminous efficiencies of the recorded objects. Fragmentation of the meteoroids is not considered within this model. Good measurements of the meteor deceleration are required. [Results] We find τ-values, as well as the shape change coefficients, of 294 meteors and fireballs with determined masses in the range of 10-6-100 kg. The derived τ-values have a median of τmedian = 2.17%. Most of them are of the order of 0.1-10%. We present how our values are obtained, compare them with data reported in the literature, and discuss several methods. A dependence of τ on the pre-atmospheric velocity of the meteor, ve, is noticeable with a relation of τ = 0.0023 ve2.3. Furthermore, a dependence of τ on the initial meteoroid mass, Me, is found with negative linear behaviour in log-log space: τ = 0.48 Me-0.47. [Conclusions] The higher luminous efficiency of fast meteors could be explained by the higher amount of energy released. Fast meteoroids produce additional emission lines that radiate more efficiently in specific wavelengths due to the appearance of the so-called second component of higher temperature. Furthermore, the negative dependence of τ on Me implies that the radiation of smaller meteoroids is more efficient. The results of this study also show the limitations of the ablation-based model for the determination of the luminous efficiency.

In this study, we investigate the ablation properties of bolides capable of producing meteorites. The casual dashcam recordings from many locations of the Chelyabinsk superbolide associated with the atmospheric entry of an 18 m in diameter near-Earth object (NEO) have provided an excellent opportunity to reconstruct its atmospheric trajectory, deceleration, and heliocentric orbit. In this study, we focus on the study of the ablation properties of the Chelyabinsk bolide on the basis of its deceleration and fragmentation. We explore whether meteoroids exhibiting abrupt fragmentation can be studied by analyzing segments of the trajectory that do not include a disruption episode. We apply that approach to the lower part of the trajectory of the Chelyabinsk bolide to demonstrate that the obtained parameters are consistent. To do that, we implemented a numerical (Runge–Kutta) method appropriate for deriving the ablation properties of bolides based on observations. The method was successfully tested with the cases previously published in the literature. Our model yields fits that agree with observations reasonably well. It also produces a good fit to the main observed characteristics of Chelyabinsk superbolide and provides its averaged ablation coefficient σ = 0.034 s km. Our study also explores the main implications for impact hazard, concluding that tens of meters in diameter NEOs encountering the Earth in grazing trajectories and exhibiting low geocentric velocities are penetrating deeper into the atmosphere than previously thought and, as such, are capable of producing meteorites and even damage on the ground., This research was funded by the research project (PGC2018-097374-B-I00, P.I. J.M.T-R), funded by FEDER/Ministerio de Ciencia e Innovación–Agencia Estatal de Investigación. MG acknowledges support from the Academy of Finland (325806). Research at the Ural Federal University was supported by the Russian Foundation for Basic Research (18-08-00074 and 19-05-00028).

The disruption of asteroids and comets produces cm-sized meteoroids that end up impacting the Earth's atmosphere and producing bright fireballs that might have associated shock waves or, in geometrically-favorable occasions excavate craters that put them into unexpected hazardous scenarios. The astrometric reduction of meteors and fireballs to infer their atmospheric trajectories and heliocentric orbits involves a complex and tedious process that generally requires many manual tasks. To streamline the process, we present a software package called SPMN 3D Fireball Trajectory and Orbit Calculator (3D-FireTOC), an automatic Python code for detection, trajectory reconstruction of meteors, and heliocentric orbit computation from video recordings. The automatic 3D-FireTOC package comprises of a user interface and a graphic engine that generates a realistic 3D representation model, which allows users to easily check the geometric consistency of the results and facilitates scientific content production for dissemination. The software automatically detects meteors from digital systems, completes the astrometric measurements, performs photometry, computes the meteor atmospheric trajectory, calculates the velocity curve, and obtains the radiant and the heliocentric orbit, all in all quantifying the error measurements in each step. The software applies corrections such as light aberration, refraction, zenith attraction, diurnal aberration and atmospheric extinction. It also characterizes the atmospheric flight and consequently determines fireball fates by using the $\alpha - \beta$ criterion that analyses the ability of a fireball to penetrate deep into the atmosphere and produce meteorites. We demonstrate the performance of the software by analyzing two bright fireballs recorded by the Spanish Fireball and Meteorite Network (SPMN)., Comment: Published on 10 April 2021

Analogues have been developed and characterised for both interplanetary dust and meteoric smoke particles. These include amorphous materials with elemental compositions similar to the olivine mineral solid solution series, a variety of iron oxides, undifferentiated meteorites (chondrites) and minerals which can be considered good terrestrial proxies to some phases present in meteorites. The products have been subjected to a suite of analytical techniques to demonstrate their suitability as analogues for the target materials.

Meteoroids impacting the Earth atmosphere are commonly classified using the PE criterion. This criterion was introduced to support the identification of the fireball type by empirically linking its orbital origin and composition characteristics. Additionally, it is used as an indicator of the meteoroid tensile strength and its ability to penetrate the atmosphere. However, the level of classification accuracy of the PE criterion depends on the ability to constrain the value of the input data, retrieved from the fireball observation, required to derive the PE value. To overcome these uncertainties and achieve a greater classification detail we propose a new formulation using scaling laws and dimensionless variables that groups all the input variables into two parameters that are directly obtained from the fireball observations. These two parameters, ${\alpha}$ and ${\beta}$, represent the drag and the mass loss rates along the luminous part of the trajectory, respectively, and are linked to the shape, strength, ablation efficiency, mineralogical nature of the projectile, and duration of the fireball. Thus, the new formulation relies on a physical basis. This work shows the mathematical equivalence between the PE criterion and the logarithm of $2{\alpha}{\beta}$ under the same PE-criterion assumptions. We demonstrate that $log(2{\alpha}{\beta})$ offers a more general formulation which does not require any preliminary constraint on the meteor flight scenario and discuss the suitability of the new formulation for expanding the classification beyond fully disintegrating fireballs to larger impactors including meteorite-dropping fireballs. The reliability of the new formulation is validated using the Prairie Network meteor observations., Comment: 15 pages, 2 figures, 1 table

Aims. The existence of asteroid complexes produced by the disruption of these comets suggests that evolved comets could also produce high-strength materials able to survive as meteorites. We chose as an example comet 2P/Encke, one of the largest object of the so-called Taurid complex. We compare the reflectance spectrum of this comet with the laboratory spectra of some Antarctic ungrouped carbonaceous chondrites to investigate whether some of these meteorites could be associated with evolved comets. Methods. We compared the spectral behaviour of 2P/Encke with laboratory spectra of carbonaceous chondrites. Different specimens of the common carbonaceous chondrite groups do not match the overall features and slope of the comet 2P/Encke. By testing anomalous carbonaceous chondrites, we found two meteorites: Meteorite Hills 01017 and Grosvenor Mountains 95551, which could be good proxies for the dark materials that formed this short-period comet. We hypothesise that these two meteorites could be rare surviving samples, either from the Taurid complex or another compositionally similar body. In any case, it is difficult to get rid of the effects of terrestrial weathering in these Antarctic finds, and further studies are needed. A future sample return from the so-called dormant comets could also be useful to establish a ground truth on the materials forming evolved short-period comets. Results. As a natural outcome, we think that identifying good proxies of 2P/Encke-forming materials might have interesting implications for future sample-return missions to evolved, potentially dormant, or extinct comets. Understanding the compositional nature of evolved comets is particularly relevant in the context of the future mitigation of impact hazard from these dark and dangerous projectiles., J.M.T.R. and S.T. acknowledge financial support from the Spanish Ministry (PGC2018-097374-B-I00, PI: JMTR). J.L.L. is grateful to ICREA Academia program and funding from Generalitat de Catalunya (2017 SGR 128). US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Acquisition and Curation Office at NASA Johnson Space Center.

(Topical Collection: Cosmic Dust from the Laboratory to the Stars, Edited by Rafael Rodrigo, Jürgen Blum, Hsiang-Wen Hsu, Detlef Koschny, Anny-Chantal Levasseur-Regourd, Jesús Martín-Pintado, Veerle Sterken and Andrew Westphal); International audience; Interplanetary dust particles and meteoroids mostly originate from comets and asteroids. Understanding their distribution in the Solar system, their dynamical behavior and their properties, sheds light on the current state and the dynamical behavior of the Solar system. Dust particles can endanger Earth-orbiting satellites and deep-space probes, and a good understanding of the spatial density and velocity distribution of dust and meteoroids in the Solar system is important for designing proper spacecraft shielding. The study of interplanetary dust and meteoroids provides clues to the formation of the Solar system. Particles having formed 4.5 billion years ago can survive planetary accretion and those that survived until now did not evolve significantly since then. Meteoroids and interplanetary dust can be observed by measuring the intensity and polarization of the zodiacal light, by observing meteors entering the Earth’s atmosphere, by collecting them in the upper atmosphere, polar ices and snow, and by detecting them with in-situ detectors on space probes.

Drolshagen, E., et al., [Context] The luminous efficiency, τ, can be used to compute the pre-Atmospheric masses of meteoroids from corresponding recorded meteor brightnesses. The derivation of the luminous efficiency is non-Trivial and is subject to biases and model assumptions. This has led to greatly varying results in the last decades of studies. [Aims] The present paper aims to investigate how a reduction in various observational biases can be achieved to derive (more) reliable values for the luminous efficiency. [Methods] A total of 281 meteors observed by the Fireball Recovery and InterPlanetary Observation Network (FRIPON) are studied. The luminous efficiencies of the events are computed using an ablation-based model. The relations of τ as a function of the pre-Atmospheric meteoroid velocity, ve, and mass, Me, are studied. Various aspects that could render the method less valid, cause inaccuracies, or bias the results are investigated. On this basis, the best suitable meteors were selected for luminous efficiency computations. [Results] The presented analysis shows the limits of the used method. The most influential characteristics that are necessary for reliable results for the τ computation were identified. We study the dependence of τ on the assumed meteoroid's density, ρ, and include improved ρ-values for objects with identified meteoroid stream association. Based on the discovered individual biases and constraints we create a pre-debiased subset of 54 well-recorded events with a relative velocity change >80%, a final height

Infrasound monitoring has proved to be effective in detection of the meteor generated shock waves. When combined with optical observations of meteors, this technique is also reliable for detecting centimeter-sized meteoroids that usually ablate at high altitudes, thus offering relevant clues that open the exploration of the meteoroid flight regimes. Since a shock wave is formed as a result of a passage of the meteoroid through the atmosphere, the knowledge of the physical parameters of the surrounding gas around the meteoroid surface can be used to determine the meteor flow regime. This study analyses the flow regimes of a data set of twenty-four centimeter-sized meteoroids for which well constrained infrasound and photometric information is available. This is the first time that the flow regimes for meteoroids in this size range are validated from observations. From our approach, the Knudsen and Reynolds numbers are calculated, and two different flow regime evaluation approaches are compared in order to validate the theoretical formulation. The results demonstrate that a combination of fluid dynamic dimensionless parameters is needed to allow a better inclusion of the local physical processes of the phenomena., 41 pages, 3 Figures and 3 Tables (in press in ApJ)

We analyse the outburst experienced by the September ∈-Perseid meteor shower on 2013 September 9. As a result of our monitoring, the atmospheric trajectory of 60 multistation events observed over Spain was obtained and accurate orbital data were derived from them. On the basis of these orbits, we have tried to determine the likely parent body of this meteoroid stream by employing orbital dissimilarity criteria. In addition, the emission spectra produced by two events belonging to this meteor shower were also recorded. The analysis of these spectra has provided information about the chemical nature of their progenitor meteoroids. We also present an estimation of the tensile strength for these particles.© 2018 The Author(s)., We acknowledge support from the Spanish Ministry of Science and Innovation (projects AYA2015-68646-P and AYA 2015-67175-P).

We describe the fall of Annama meteorite occurred in the remote Kola Peninsula (Russia) close to Finnish border on April 19, 2014 (local time). The fireball was instrumentally observed by the Finnish Fireball Network. From these observations the strewnfield was computed and two first meteorites were found only a few hundred meters from the predicted landing site on May 29th and May 30th 2014, so that the meteorite (an H4-5 chondrite) experienced only minimal terrestrial alteration. The accuracy of the observations allowed a precise geocentric radiant to be obtained, and the heliocentric orbit for the progenitor meteoroid to be calculated. Backward integrations of the orbits of selected near-Earth asteroids and the Annama meteoroid showed that they rapidly diverged so that the Annama meteorites are unlikely related to them. The only exception seems to be the recently discovered 2014UR116 that shows a plausible dynamic relationship. Instead, analysis of the heliocentric orbit of the meteoroid suggests that the delivery of Annama onto an Earth-crossing Apollo type orbit occurred via the 4:1 mean motion resonance with Jupiter or the nu6 secular resonance, dynamic mechanisms that are responsible for delivering to Earth most meteorites studied so far., Comment: 14 pages, 4 figures and 4 tables

Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian environment, and this meteorite has features that may record early processes. These features include a highly fractured texture, gases trapped during one or more impact events or during formation of the rock, and spherical Fe‐Mg‐Ca carbonates. In this study, we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events. The petrographic features and compositional properties of these carbonates indicate that at least two pulses of Mg‐ and Fe‐rich solutions saturated the rock. Those two generations of carbonates can be distinguished by a very sharp change in compositions, from being rich in Mg and poor in Fe and Mn, to being poor in Mg and rich in Fe and Mn. Between these two generations of carbonate is evidence for fracturing and local corrosion., This research has been funded by the Spanish Ministry of Science and Innovation (projects: AYA2011‐26,522, AYA 2015‐67175‐P, CTQ2015‐62,635‐ERC, and CTQ2014‐60,119‐P to which J.M. Trigo‐Rodríguez and C.E. Moyano‐Cambero acknowledge financial support). The UK Science and Technology Facilities Council is also thanked for funding through grants ST/H002960/1, ST/K000942/1, and ST/L002167/1. ICN2 and ICMAB acknowledge support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grants SEV‐2013‐0295 and SEV‐2015‐0496, respectively.

Seven double-station α-Capricornid bolides with absolute magnitudes ranging from −6 to −10 are analyzed. These events were imaged between 2011 and 2013 in the framework of the continuous fireball monitoring and meteor spectroscopy campaign developed by the SPanish Meteor Network (SPMN). Their atmospheric trajectory is calculated, together with the orbit in the Solar System of the progenitor meteoroids and the tensile strength of these particles. Their emission spectra are also discussed, and the relative abundances of the main rock-forming chemical elements contained in these meteoroids are estimated. An overabundance of Mg with respect to the expected value for chondritic materials is inferred for most of these particles, although the spectra also reveal differences in the composition of α-Capricornid meteoroids that allow us to derive information about the parent body of this stream.

We analyze here two very bright fireballs produced by the ablation in the atmosphere of two large meteoroids in 2009 and 2010. These slow-moving and deep-penetrating events were observed over Spain in the framework of our Spanish Fireball Network continuous meteor monitoring campaign. The analysis of the emission spectrum imaged for one of these fireballs has provided the first clues about the chemical nature of the progenitor meteoroids. The orbital parameters of these particles suggests a likely association with the recently identified July rho-Herculid meteoroid stream. In addition, considerations about the likely parent body of this stream are also made on the basis of orbital dissimilarity criteria. This orbital analysis reveals that both meteoroids and PHA 2007LQ19 exhibit a similar evolution during a time period of almost 8,000 years, which suggests that either this NEO is the potential parent of these particles or that this NEO and both meteoroids had a common progenitor in the past., Accepted for publication in Monthly Notices of the Royal Astronomical Society(MNRAS) on 2014 June 23

When comet nuclei approach the Sun, the increasing energy flux through the surface layers leads to sublimation of the underlying ices and subsequent outgassing that promotes the observed emission of gas and dust. While the release of gas can be straightforwardly understood by solving the heat-transport equation and taking into account the finite permeability of the ice-free dust layer close to the surface of the comet nucleus, the ejection of dust additionally requires that the forces binding the dust particles to the comet nucleus must be overcome by the forces caused by the sublimation process. This relates to the question of how large the tensile strength of the overlying dust layer is. Homogeneous layers of micrometer-sized dust particles reach tensile strengths of typically 10 3 to 10 4 Pa . This exceeds by far the maximum sublimation pressure of water ice in comets. It is therefore unclear how cometary dust activity is driven. To solve this paradox, we used the model by Skorov and Blum (Skorov, Y.V., Blum, J. 2012. Icarus 221, 361–11), who assumed that cometesimals formed by gravitational instability of a cloud of dust and ice aggregates and calculated for the corresponding structure of comet nuclei tensile strength of the dust-aggregate layers on the order of 1 Pa. Here we present evidence that the emitted cometary dust particles are indeed aggregates with the right properties to fit the model by Skorov and Blum. Then we experimentally measure the tensile strengths of layers of laboratory dust aggregates and confirm the values derived by the model. To explain the comet activity driven by the evaporation of water ice, we derive a minimum size for the dust aggregates of ∼1 mm, in agreement with meteoroid observations and dust-agglomeration models in the solar nebula. Finally we conclude that cometesimals must have formed by gravitational instability, because all alternative formation models lead to higher tensile strengths of the surface layers.

Among the most astonishing astronomical phenomena are the extremely bright bolides produced by the entry of large meteoroids into the Earth’s atmosphere. These events are rare and unexpected because current telescopic surveys are still missing meter-sized meteoroids, particularly those of dark nature and presumably cometary origin. In this work we present the analysis of two very bright fireballs of such origin recently observed over Spain. The first of these was recorded on September 25, 2010, while the second one took place on August 23, 2012. With an absolute magnitude of −18 and −17, respectively, these sporadic events fall within the superbolide category. Their atmospheric trajectory is calculated, together with the heliocentric orbit of the parent meteoroids. Other physical properties of these particles are estimated, such as their preatmospheric mass and tensile strength. The emission spectrum recorded for one of these events is also discussed. Our analysis indicates that none of these superbolides was a meteorite-dropping event. From their orbital parameters, a cometary nature for the parent meteoroids is inferred.

We present the analysis of five bright fireballs observed over Spain and France between 2010 and 2012. Their absolute magnitude ranged between −9.0 and −11.5. Radiant and orbital data indicate that these events were associated with the Taurid meteoroid stream. Their trajectory in the atmosphere is calculated and the heliocentric orbit of the meteoroids is obtained. The emission spectra produced by three of these fireballs are also discussed, and the chemical nature of the parent impactors is inferred, together with different physical parameters of these particles such as the meteoroid mass and tensile strength. On the basis of these results, the ability of Taurid meteoroids to produce meteorites is discussed.

The results of the atmospheric trajectory, radiant, heliocentric orbit, and preliminary strewn field calculations for an extremely bright slow-moving fireball are presented. In the evening hours of July 23, 2008, a bright object entered Earth's atmosphere over Tajikistan. The fireball had a −20.3 maximum absolute magnitude and a spectacularly long persistent dust trail remained visible over a widespread region of Tajikistan for about 28 minutes after sunset. The fireball was also recorded by a visible-light satellite system at 14 h 45 min 25 s UT, and the dust trail was imaged by video and photocameras. A unique aspect of this event is that it was detected by two infrasound and five seismic stations too. The bolide was first recorded at a height of 38.2 km, reached its maximum brightness at a height of 35.0 km, and finished at a height of 19.6 km. The first breakup occurred under an aerodynamic pressure of approximately 1.6 MPa, similar to the values derived for breakups of the scarcely reported meteorite-dropping bolides. The fireball's trajectory and dynamic results suggest that meteorite survival is likely. The meteoroid followed an Apollo-like asteroid orbit comparable to those derived for previously recovered meteorites with accurately known orbits.

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short-lived radionuclides are compatible with an atmospheric pre-entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The 10Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre-entry radius. © The Meteoritical Society, 2017.

The Ursid meteor shower is an annual shower that usually shows little activity. However, its Zenith Hourly Rate sometimes increases, usually either when its parent comet, 8P/Tuttle, is close to its perihelion or its aphelion. Outbursts when the comet is away from perihelion are not common and outburst when the comet is close to aphelion are extremely rare. The most likely explanation offered to date is based on the orbital mean motion resonances. The study of the aphelion outburst of December 2000 provided a means of testing that hypothesis. A new aphelion outburst was predicted for December 2014. The Spanish Meteor Network in collaboration with the French Fireball Recovery and InterPlanetary Observation Network set up a campaign to monitor this outburst and eventually retrieve orbital data that expands and confirms previous preliminary results and predictions. Despite unfavourable weather conditions over the South of Europe over the relevant time period precise trajectories from multi-station meteor data recorded over Spain were obtained, as well as orbital and radiant information for four Ursid meteors. The membership of these four meteors to the expected dust trails that were to provoke the outburst is discussed, and we characterize the origin of the outburst in the dust trail produced by the comet in the year 1392 A.D., Comment: 12 pages, 6 figures, 7 tables

We present new orbital data and dynamic results pointing towards the origin of the Northern χ-Orionid meteoroid stream, which is a part of the Taurid meteoroid complex. A new software package was developed to establish the potential parent bodies of meteoroid streams based on the similarity of their orbits. The analysis of a Northern χ-Orionid fireball observed on 2011 December 6 identified two potential parent bodies: the near-Earth object (NEO) 2002XM35 (previously proposed as the parent of this meteoroid stream) and the more recently discovered potentially hazardous asteroid 2008XM1. The calculation of the evolution of the orbital elements performed by using the Mercury 6 symplectic integrator supports the idea that 2008XM1 is a better parent body. Our data sample was expanded by including also in the calculations the mean orbit of the χ-Orionid stream. The results are consistent with the fragmentation of a larger body in the past that could give rise to both NEOs and the Northern χ-Orionid stream. To confirm this, further observations to improve the orbital elements of these asteroids should be attempted before the objects are lost. The analysis of the emission spectrum recorded for this fireball supports a primitive nature for these meteoroids., We acknowledge support from the Spanish Ministry of Science and Innovation (projects AYA2009-13227, AYA2009-14000-C03-01 and AYA2011-26522), CSIC (grant 201050I043) and Junta de Andalucia (project P09-FQM-4555).

Accurate orbital data obtained for the recently discovered γ -Ursae Minorids meteoroid stream during the 2010 and 2011 Spanish Meteor Network and Finnish Fireball Network observing ampaigns are presented. In particular, we focus on an outburst detected in 2010 and on the analysis of the first emission spectrum recorded for a member of this meteoroid stream. An array of high-sensitivity CCD video devices operating from different locations in Spain and Finland was used to perform this study. We have obtained precise trajectory, radiant and orbital information for seven members of this stream. Considerations about its likely parent body based on orbital dissimilarity criteria are made. We also present an estimation of the tensile strength for these meteoroids and a unique emission spectrum of a γ -Ursae inorid fireball that reveals that the main rocky components have chondritic abundances. Ministerio de Ciencia e Innovación AYA2009-13227, AYA2009-14000-C03-01, AYA2011-26522, AYA2011-30106-C02-01 CSIC #201050I043 Junta de Andalucía P09-FQM-4555

A crucial topic in planetology research is establishing links between primitive meteorites and their parent asteroids. In this study we investigate the feasibility of a connection between asteroids similar to 21 Lutetia, encountered by the Rosetta mission in July 2010, and the CH3 carbonaceous chondrite Pecora Escarpment 91467 (PCA 91467). Several spectra of this meteorite were acquired in the ultraviolet to near-infrared (0.3 to 2.2 {\mu}m) and in the mid-infrared to thermal infrared (2.5 to 30.0 {\mu}m or 4000 to ~333 cm^-1), and they are compared here to spectra from the asteroid 21 Lutetia. There are several similarities in absorption bands and overall spectral behavior between this CH3 meteorite and 21 Lutetia. Considering also that the bulk density of Lutetia is similar to that of CH chondrites, we suggest that this asteroid could be similar, or related to, the parent body of these meteorites, if not the parent body itself. However, the apparent surface diversity of Lutetia pointed out in previous studies indicates that it could simultaneously be related to other types of chondrites. Future discovery of additional unweathered CH chondrites could provide deeper insight in the possible connection between this family of metal-rich carbonaceous chondrites and 21 Lutetia or other featureless, possibly hydrated high-albedo asteroids., Comment: 26 pages, 7 figures and 2 tables, Meteoritics and Planetary Science, manuscript #2225 (2016)

We have assembled data on thirteen cases of meteorite falls with accurate tracking data on atmospheric passage. In all cases we estimate the bulk strength of the object corresponding to its earliest observed or inferred fragmentation in the high atmosphere, and can compare these values with measured strengths of meteorites in the taxonomic class for that fall. In all thirteen cases the strength corresponding to earliest observed or inferred fragmentation is much less than the compressive or tensile strength reported for that class of stony meteorites. We find a more random relation between bulk sample strength and sample mass than is suggested by a commonly used empirical power law. We estimate bulk strengths on entry being characteristically of the order of 10 -1 to 10 -2 times the tensile strengths of recovered samples.

We have carried out a continuous multi-band photometric monitoring of the nuclear activity of comet 29P/Schwassmann-Wachmann 1 from 2008 to 2010. Our main aim has been to study the outburst mechanism on the basis of a follow-up of the photometric variations associated with the release of dust. We used a standardized method to obtain the 10 arc-sec nucleus photometry in the V, R, and I filters of the Johnson-Kron-Cousins system, being accurately calibrated with standard Landolt stars. Production of dust in the R and I bands during the 2010 Feb. 3 outburst has been also computed. We conclude that the massive ejection of large (optically-thin) particles from the surface at the time of the outburst is the triggering mechanism to produce the outburst. Ulterior sublimation of these ice-rich dust particles during the following days induces fragmentation, generating micrometer-sized grains that increase the dust spatial density to produce the outburst in the optical range due to scattering of sun light. The material leaving the nucleus adopts a fan-like dust feature, formed by micrometer-sized particles that are decaying in brightness as it evolved outwards. By analyzing the photometric signal measured in a standardized 10-arcsec aperture using the Phase Dispersion Minimization technique we have found a clear periodicity of 50 days. Remarkably, this value is also consistent with an outburst frequency of 7.4 outbursts/year deduced from the number of outbursts noticed during the effective observing time.

–The fall of the Berduc meteorite took place on April 7, 2008, at 01 h 02 min 28 s ± 1 s UTC. A daylight fireball was witnessed by hundreds of people from Argentina and Uruguay, and also recorded by an infrasound array in Paraguay. From the available data, the fireball trajectory and radiant have been reconstructed with moderate accuracy. The modeled trajectory was tested to fit the infrasound and strewn field data. From the computed apparent radiant a = 87 ± 2 and d = )11 ± 2 and taking into account a range of plausible initial velocities, we obtained a range of orbital solutions. All of them suggest that the progenitor meteoroid originated from the main asteroid belt and followed an orbit of low inclination. Based on petrography, mineral chemistry, magnetic susceptibility, and bulk chemistry, the Berduc meteorite is classified as an L6 ordinary chondrite.

We demonstrate that a massive asymptotic giant branch (AGB) star is a good candidate as the main source of short-lived radionuclides in the early solar system. Recent identification of massive (4-8 solar masses) AGB stars in the Galaxy, which are both lithium- and rubidium-rich, demonstrates that these stars experience proton captures at the base of the convective envelope (hot bottom burning), together with high-neutron density nucleosynthesis with 22Ne as a neutron source in the He shell and efficient dredge-up of the processed material. A model of a 6.5 solar masses star of solar metallicity can simultaneously match the abundances of 26Al, 41Ca, 60Fe, and 107Pd inferred to have been present in the solar nebula by using a dilution factor of 1 part of AGB material per 300 parts of original solar nebula material, and taking into account a time interval between injection of the short-lived nuclides and consolidation of the first meteorites equal to 0.53 Myr. Such a polluting source does not overproduce 53Mn, as supernova models do, and only marginally affects isotopic ratios of stable elements. It is usually argued that it is unlikely that the short-lived radionuclides in the early solar system came from an AGB star because these stars are rarely found in star forming regions, however, we think that further interdisciplinary studies are needed to address the fundamental problem of the birth of our solar system., Comment: 27 pages, 5 tables, and 1 figure

Puerto Lapice is a new eucrite fall (Castilla-La Mancha, Spain, 10 May 2007). In this paper, we report its detailed petrography, magnetic characterization, mineral and bulk chemistry, oxygen and noble gas isotope systematics, and radionuclide data. Study of four thin sections from two different specimens reveal that the meteorite is brecciated in nature, and it contains basaltic and granulitic clasts, as well as recrystallized impact melt and breccia fragments. Shock veins are ubiquitous and show evidence of at least three different shock events. Bulk chemical analyses suggest that Puerto Lapice belongs to the main group of basaltic eucrites, although it has a significantly higher Cr content. Oxygen isotopes also confirm that the meteorite is a normal member of the HED suite. Noble gas abundances show typical patterns, with dominant cosmogenic and radiogenic contributions, and indicate an average exposure age of 19 ± 2 Ma, and a Pu-fission Xe age well within typical eucrite values. Cosmogenic radionuclides suggest a preatmospheric size of about 20-30 cm in diameter.

The fall of the Puerto Lapice eucrite occurred on May 10, 2007, at 17 h 57 m 30 ± 30 s UTC. Its daylight fireball was witnessed by hundreds of people from Spain, and produced a meteorite fall associated with a large strewn field of fragments. There were no direct pictures of the fireball, but several pictures of the fireballs train were taken from different locations in Spain. Additional theodolite calibrations of visual records were made in order to find the most probable fireball trajectory based on the available data. The shape of the meteorite strewn field was considered as well. Although the orbit of the Puerto Lapice meteoroid could not be computed due to the absence of velocity data, we assumed a likely range of geocentric velocities and computed a range of possible orbits. All solutions show that the body was in an Apollo-type orbit, with low inclination and perihelion distance just below 1 astronomical unit (AU). This is the first case that an orbit can be discussed for an HED meteorite fall.

10 pages, 6 figures, 5 tables, The fall of the Cali meteorite took place on 6 July 2007 at 16 h 32 ± 1 min local time (21 h 32 ± 1 min UTC). A daylight fireball was witnessed by hundreds of people in the Cauca Valley in Colombia from which 10 meteorite samples with a total mass of 478 g were recovered near 3°24.3'N, 76°30.6'W. The fireball trajectory and radiant have been reconstructed with moderate accuracy. From the computed radiant and from considering various plausible velocities, we obtained a range of orbital solutions that suggest that the Cali progenitor meteoroid probably originated in the main asteroid belt. Based on petrography, mineral chemistry, magnetic susceptibility, fhermoluminescence, and bulk chemistry, the Cali meteorite is classified as an H/L4 ordinary chondrite breccia, This work was partially supported by NASA Cosmochemistry grants NNH05AB65I to JNG and NNG06GF95G to AER and NASA Discovery Data Analysis grant NNX08G17G to DWGS. JMTR also thanks CSIC for a JAE-Doc research contract

The extremely porous structure and low strength of most comets and their fragments is opposed to the properties observed in relatively pristine chondritic asteroids, even although both are sharing important chemical similitude. Laboratory experiments and observational evidence suggest that the original extremely porous aggregates that were born from the protoplanetary-disk-forming materials were highly retentive of water and organic compounds present in their forming environment. After consolidation, many of them experienced a particular dynamic history. Some bodies, quickly scattered during the formation of the giant planets and later stored in the Kuiper Belt (KB) or the Oort Cloud (OC) regions, would have suffered a lower degree of impact processing than previously thought. In such category would be comet 81P/Wild 2, whose materials have not experienced aqueous alteration. Other bodies originally volatile-rich that were transiting other regions with higher impact rate were experiencing progressively significant compaction processing, together with subsequent aqueous alteration and loss of volatiles. The release of water from hydrated minerals or interior ices, participated in soaking the forming materials, and transforming their initial mineralogy and physical properties. As a consequence of the physico-chemical evolution promoted by impact processing of undifferentiated bodies, most of the bodies present in the inner solar system are not representative of the planetesimals. Thus, highly porous progenitors and their fragments are the preferential sources of water and organics to the early Earth, even in higher amounts than previously thought.

Relatively small amounts (typically between 2-200 parts per million) of presolar grains have been preserved in the matrices of chondritic meteorites. The measured abundances of the different types of grains are highly variable from one chondrite to another, but are higher in unequilibrated chondrites that have experienced little or no aqueous alteration and/or metamorphic heating than in processed meteorites. A general overview of the abundances measured in presolar grains (particularly the recently identified presolar silicates) contained in primitive chondrites is presented. Here we will focus on the most primitive chondrite groups, as typically the highest measured abundances of presolar grains occur in primitive chondrites that have experienced little thermal metamorphism. Looking at the most aqueously altered chondrite groups, we find a clear pattern of decreasing abundance of presolar silicate grains with increasing level of aqueous alteration. We conclude that the measured abundances of presolar grains in altered chondrites are strongly biased by their peculiar histories. Scales quantifying the intensity of aqueous alteration and shock metamorphism in chondrites could correlate with the content in presolar silicates. To do this it would be required to infer the degree of destruction or homogenization of presolar grains in the matrices of primitive meteorites. To get an unbiased picture of the relative abundance of presolar grains in the different regions of the protoplanetary disk where first meteorites consolidated, future dedicated studies of primitive meteorites, IDPs, and collected materials from sample-return missions (like e.g. the planned Marco Polo) are urgently required., 15 pages, 3 figures, published in PASA as part of the Proceedings of the 2008 Torino Conference "The Origin of the Elements Heavier than Iron"

Aims. We carried out a continuous monitoring of comet 29P/Schwassmann-Wachmann 1 by using medium aperture telescopes with the aim of studying the activity and outburst mechanisms of this comet on the basis of photometric variations. Methods. We used a standardized method to obtain the coma photometry in the R filter of the Johnson-Kron-Cousins system. Some abrupt changes observed in the brightness of SW1 suggest important variations in surface activity with time. Results. During our 2002-2007 observational campaign we detected 28 outbursts (of 1 mag or larger) in 29P/Schwassmann-Wachmann 1. A typical outburst is characterized by a rapid increase towards maximum (in a few hours) and a slower decrease toward the quiescent level (in 3-4 days). Given the effective observing time, the average outburst rate is 7.3 events per year. Despite well-sampled data, no signs of a clear periodicity in the outburst occurrence has been found, thus confirming the unpredictability of the activity of this comet.

By using high-resolution, low-scan-rate, all-sky CCD cameras, the SPanish Meteor Network (SPMN) is currently monitoring meteor and fireball activity on a year round basis. Here are presented just a sampling of the accurate trajectory, radiant and orbital data obtained for meteors imaged simultaneously from two SPMN stations during the continuous 2006–2007 coverage of meteor and fireball monitoring. Typical astrometric uncertainty is 1–2 arc min, while velocity determination errors are of the order of 0.1–0.5 km/s, which is dependent on the distance of each event to the station and its particular viewing geometry. The cameras have demonstrated excellent performance for detecting meteor outbursts. The recent development of automatic detection software is also providing real-time information on the global meteor activity. Finally, some examples of the all-sky CCD cameras applications for detecting unexpected meteor activity are given.

Most meteorites are fragments from recent collisions experienced in the asteroid belt. In such a hypervelocity collision, the smaller collision partner is destroyed, whereas a crater on the asteroid is formed or it is entirely disrupted, too. The present size distribution of the asteroid belt suggests that an asteroid with a 100 km radius is encountered 1014 times during the lifetime of the solar system by objects larger than 10 cm in radius; the formed craters cover the surface of the asteroid about 100 times. We present a Monte Carlo code that takes into account the statistical bombardment of individual infinitesimally small surface elements, the subsequent compaction of the underlying material, and the formation of a crater and a regolith layer. For the entire asteroid, 10,000 individual surface elements are calculated. We compare the ejected material from the calculated craters with the shock stage of meteorites with low petrologic type and find that these most likely stem from smaller parent bodies that do not possess a significant regolith layer. For larger objects, which accrete a regolith layer, a prediction of the thickness depending on the largest visible crater can be made. Additionally, we compare the crater distribution of an object initially 100 km in radius with the shape model of the asteroid (21) Lutetia, assuming it to be initially formed spherical with a radius that is equal to its longest present ellipsoid length. Here we find the shapes of both objects to show resemblance to each other., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids. Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young's modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and, therefore higher values imply more efficient impacts. In the Chelyabinsk meteorite, the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and, therefore, increase the momentum multiplication. These results are relevant considering the growing interest in missions to test asteroid deflection, such as the recent collaboration between the European Space Agency and NASA, known as the Asteroid Impact and Deflection Assessment mission., Comment: 2 Tables, 4 Figures, and 19 pages in Astrophysical Journal (2017)

The activity of the Quadrantids in January during several years (2008, 2010, 2011 and 2012) has been investigated in the framework of the SPanish Meteor Network (SPMN). For this purpose, an array of high-sensitivity CCD video devices and CCD all-sky cameras have been used to obtain multi-station observations of these meteors. These allowed us to obtain precise radiant and orbital information about this meteoroid stream. This paper presents a large set of orbital data (namely, 85 orbits) of Quadrantid meteoroids. Most meteors produced by these particles were recorded during the activity peak of this shower. Besides, we discuss four Quadrantid emission spectra. The tensile strength of Quadrantid meteoroids has been also obtained., Comment: Accepted for publication in Icarus on 18 April 2016

During 2006 the SPanish Meteor Network (SPMN) set up three automated video stations in Andalusia for increasing the atmospheric coverage of the already existing low-scan-rate all-sky CCD systems. Despite their initially thought complementary nature, sensitive video cameras have been employed to setup an automatic meteor detection system that provides valuable real-time information on unusual meteor activity, and remarkable fireball events. In fact, during 2006 SPMN video stations participated in the detection of two unexpected meteor outbursts: Orionids and Comae Berenicids. The three new SPMN stations guarantee almost a continuous monitoring of meteor and fireball activity in Andalusia (Spain) and also increase the chance of future meteorite recoveries. A description of the main characteristics of these new observing video stations and some examples of the trajectory, radiant and orbital data obtained so far are presented here.

A daylight bolide was observed over Galicia (NW Spain) and Minho (N. Portugal) on March 1, 2005 at 15 h10 min ± 3 min UTC. We interviewed 23 eyewitnesses of the event in order to obtain the azimuth, altitude, and slope of the fireball’s trajectory. Reports suggest an atmospheric ending height below 20 km, indicating that meteorite survival was likely. From the reconstructed trajectory and the fireball’s duration, we obtained the approximate heliocentric orbits for the meteoroid. Assuming an entry velocity higher than 20 km s−1 which is consistent with its estimated duration, the meteoroid originated in the asteroid belt.

We present laboratory experiments on the formation of macroscopic dust aggregates. The centimeter-sized highly porous bodies are produced by random ballistic deposition from individual micrometer-sized dust particles. We find packing densities between 0.07 and 0.15 for uncompressed samples, dependent on the shape and size distribution of the constituent dust grains. Impacts into these bodies are simulated by uniaxial compression experiments. We find that the maximum compression, equivalent to the highest protoplanetary impact velocities of ~50 m s-1, increases the packing density to 0.20-0.33. Tensile strength measurements with our laboratory samples yield values in the range 200-1100 Pa for slightly compressed samples. We review packing densities and tensile strengths found for primitive solar system bodies, e.g., for comets, primitive meteorites, and meteoroids. We find a consistency between packing densities and tensile strengths of our laboratory samples with those from cometary origin.

Meteoroid behaviour during atmospheric interaction provides clues about the strength and density of cometary disintegration products, establishing a bridge between different research fields. We have estimated the strength of cometary meteoroids by studying meteor ablation light curves measured accurately from multiple-station meteor observation programmes. Our approach assumes that the typical height for meteoroid fragmentation is associated with the peak of meteor luminosity. The strength of cometary meteoroids is independent of the entry velocity and very similar for cometary streams with similar ages. Meteoroids from periodic comets have typical strength of ∼10 4 dyn cm -2 . The only exception among the studied comets is the extremely fluffy particles from 21P/Giacobini-Zinner that exhibit ∼4×10 2 dyn cm -2 . Finally, evolved bodies, e.g. 2P/Encke and 3200 Phaeton, release the toughest meteoroids. We suggest that the main physical difference between cometary particles reaching the Earth from several sources could be a different degree of compaction arising from different physical processing of cometary nuclei by collisional processes, thermal and, perhaps, aqueous alteration. Meteor data suggest that highly processed cometary nuclei produce the meteoroids with the largest tensile strength values while 'pristine comets' are producing meteoroids with the lowest strength values characteristic of bodies with a low degree of compaction.