The internal structure and strength of small asteroids and large meteoroids is poorly known. Observation of bright fireballs in the Earth's atmosphere can prospect meteoroid structure by studying meteoroid fragmentation during the flight. Earlier evaluations showed that meteoroid strength is significantly lower than that of the recovered meteorites. We present detailed study of atmospheric fragmentation of seven meteorite falls, all ordinary chondrites, and 14 other fireballs, where meteorite fall was predicted but the meteorites, probably also ordinary chondrites, were not recovered. All observations were made by the autonomous observatories of the European Fireball Network and include detailed radiometric light curves. A model, called the semi-empirical fragmentation model, was developed to fit the light curves and decelerations. Videos showing individual fragments were available in some cases. The results demonstrated that meteoroids do not fragment randomly but in two distinct phases. The first phase typically corresponds to low strengths of 0.04 - 0.12 MPa. In 2/3 of cases, the first phase was catastrophic or nearly catastrophic with at least 40% of mass lost. The second phase corresponds to 0.9 - 5 MPa for confirmed meteorite falls and to somewhat lower strengths, from about 0.5 MPa for smaller meteoroids. All these strengths are lower than tensile strengths of ordinary chondritic meteorites cited in the literature, 20 - 40 MPa. We interpret the second phase as being due by cracks in meteoroids and the first phase as separation of weakly cemented fragments, which reaccumulated at surfaces of asteroids after asteroid collisions.
Eta-Virginids: another asteroidal meteoroid stream
Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Astronomical Institute of the Slovak Academy of Sciences（斯洛伐克科学院天文研究所）；Österreichischer Astronomischer Verein（奥地利天文协会）
Meteor clusters: tracing meteoroid fragmentation in near-Earth space
Astronomical Institute, Czech Academy of Sciences（捷克科学院天文研究所）；Faculty of Mathematics, Physics and Informatics, Comenius University（康斯坦丁神学院数学、物理与信息学院）；Institut de Mécanique Céleste et de Calcul des Éphémérides（天体力学与星历计算研究所）；National Astronomical Observatory（国立天文台）
High precision meteor observations with the Canadian Automated Meteor Observatory -- Data reduction pipeline and application to meteoroid mechanical strength measurements
Multi-Arrival Infrasound from Meteoroids: Fragmentation Signatures versus Propagation Effects in a Fine-Scale Layered Atmosphere
Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences（俄罗斯科学院奥布霍夫大气物理研究所）；Sandia National Laboratories（桑迪亚国家实验室）；Western University（韦仕敦大学）；Moscow State University（莫斯科国立大学）
Decameter-sized Earth Impactors -- II: A Bayesian Inference Approach to Meteoroid Ablation Modeling
Department of Physics and Astronomy, University of Western Ontario（韦仕敦大学物理与天文学系）；Western Institute for Earth and Space Exploration, University of Western Ontario（韦仕敦大学西部地球与空间探索研究所）
Multi-Sensor Trajectory Reconstruction of the 24 April 2025 Alaska Fireball and Implications for Planetary Defense
Sandia National Laboratories（桑迪亚国家实验室）；Geophysical Institute, University of Alaska Fairbanks（阿拉斯加费尔班克斯大学地球物理研究所）；Astromaterials Research and Exploration Science Division, NASA Johnson Space Center（NASA约翰逊航天中心天体材料研究与探索科学部）；Department of Physics and Astronomy, Western University（韦斯顿大学物理与天文系）；Astronomical Society Istra Pula（伊斯特拉普拉天文协会）；SETI Institute（SETI研究所）；NASA Ames Research Center（NASA艾姆斯研究中心）；Osaka Kyoiku University（大阪教育大学）；Department of Physics & Astronomy, University of Alaska Anchorage（阿拉斯加安克雷奇大学物理与天文系）
