Eine spannende Lektüre zum Fall! 

The anomalous polymict ordinary chondrite breccia of Elmshorn (H3-6)—Late reaccretion after collision between two ordinary chondrite parent bodies, complete disruption, and mixing possibly about 2.8 Gyr ago

Addi Bischoff, Markus Patzek, Romain M. L. Alosius, Jean-Alix Barrat, Jasper Berndt, Henner Busemann, Detlev Degering, Tommaso Di Rocco, Mattias Ek, Jérôme Gattacceca, Jose R. A. Godinho, Dieter Heinlein, Daniela Krietsch, Colin Maden, Oscar Marchhart, Martin Martschini, Silke Merchel, Andreas Pack, Stefan Peters, Miriam Rüfenacht, Jochen Schlüter, Maria Schönbächler, Aleksandra Stojic, Jakob Storz, Wolfgang Tillmann, Alexander Wieser, Karl Wimmer, Reiner Zielke

MAPS, Version of Record online: 29 May 2024

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"Elmshorn fell April 25, 2023, about 30?km northwest of the city of Hamburg (Germany). Shortly after the fall, 21 pieces were recovered totaling a mass of 4277 g. Elmshorn is a polymict and anomalous H3-6 chondritic, fragmental breccia. The rock is a mixture of typical H chondrite lithologies and clasts of intermediate H/L (or L, based on magnetic properties) chondrite origin. In some of the 21 pieces, the H chondrite lithologies dominate, while in others the H/L (or L) chondrite components are prevalent. The H/L chondrite assignment of these components is based on the mean composition of their olivines in equilibrated type 4 fragments (~Fa21–22). The physical properties like density (3.34g cm-3) and magnetic susceptibility (logX  <5.0, with X in 10-9 m3 kg-1) are typical for L chondrites, which is inconsistent with the oxygen isotope compositions: all eight O isotope analyses from two different fragments clearly fall into the H chondrite field. Thus, the fragments found in the strewn field vary in mineralogy, mineral chemistry, and physical properties but not in O isotope characteristics. The sample most intensively studied belongs to the stones dominated by H chondrite lithologies. The chemical composition and nucleosynthetic Cr and Ti isotope data are typical for ordinary chondrites. The noble gases in Elmshorn represent a mixture between cosmogenic, radiogenic, and primordially trapped noble gases, while a solar wind component can be excluded. Because the chondritic rock of Elmshorn contains (a) H chondrite parent body interior materials (of types 5 and 6), (b) chondrite parent body near-surface materials (of types 3 and 4), (c) fragments of an H/L chondrite (dominant in many stones), (d) shock-darkened fragments, and (e) clasts of various types of impact melts but no solar wind-implanted noble gases, the different components cannot have been part of a parent body regolith. The most straightforward explanation is that the fragmental breccia of Elmshorn represents a reaccreted rock after a catastrophic collision between an H chondrite parent body and another body with H/L (or L) chondrite characteristics but with deviating O isotope values (i.e. that of H chondrites), complete disruption of the bodies, mixing, and reassembly. This is the only straightforward way that the implantation of solar wind gases could have been avoided in this kind of complex breccia. The gas retention ages of about 2.8 Gyr possibly indicate the closure time after the catastrophic collision between H and H/L (or L) chondrite parent bodies, while the cosmic ray exposure age for Elmshorn, which had a preatmospheric radius of 25–40 cm, is ~17–20 Myr."

Gratulation!

   Jetzt muss es nur noch im MetBull berichtigt werden.

  Sigrid

Interessanter Vortrag, danke für den Link, Jens.

  Sigrid

Hier eine erste Veröffentlichung zum beeindruckenden Ereignis:

The 18 May 2024 superbolide over the Iberian Peninsula: USG space sensors and ground-based independent observations

Eloy Peña-Asensio, Pau Grèbol-Tomàs, Josep M. Trigo-Rodríguez, Pablo Ramírez-Moreta, Rainer Kresken

Submitted to MNRAS, Preprint 27 May 2024, geändert am 28. Mai (version 2)

Version 2 (28 Mai 2024): "On 18 May 2024, a superbolide traversed the western part of the Iberian Peninsula, culminating its flight over the Atlantic Ocean and generating significant media attention. This event was caused by a weak carbonaceous meteoroid of 89.8±0.4 cm, with a density of 1660 kg m-3, entering the atmosphere at 41.6 km/s-1 with an angle of 10.9°. The luminous phase started at 138 km and ended at an altitude of 54 km. The meteoroid's heliocentric orbit was characterized by an inclination of 15.4°, a high eccentricity of 0.965, a semi-major axis of 3 au, and a notably short perihelion distance of 0.11 au. The superbolide was recorded by multiple ground-based stations of the Spanish Meteor Network (SPMN), the European Space Agency (ESA), and the U.S. Government (USG) space sensors. Our analysis shows a relatively good agreement with the radiant and velocity data reported by the Center for Near-Earth Object Studies (CNEOS), with a deviation of 1° and 1.2 km/s-1, respectively. Due to the absence of observable deceleration, we successfully reconciled satellite radiometric data with a purely dynamic atmospheric flight model, constraining the meteoroid's mass and coherently fitting its velocity profile. The inferred bulk density and aerodynamic strength of the meteoroid from the flight model are compatible with the properties recently measured for sample-returned materials from asteroid Bennu. The physical properties and the orbital results suggest that this meteoroid originated from a recent disruption of a comet, indicating the existence of hazardous meter-sized projectiles arriving on Earth from objects formed in the distant regions of the Solar System."