Ioannis Baziotis | Searcharxiv

arXiv2025

Catastrophic disruption of asteroid 2023 CX1 and implications for planetary defense

Mitigation of the threat from airbursting asteroids requires an understanding of the potential risk they pose for the ground. How asteroids release their kinetic energy in the atmosphere is not well understood due to the rarity of significant impacts. Ordinary chondrites, in particular L chondrites, represent a frequent type of Earth-impacting asteroids. Here, we present the first comprehensive, space-to-lab characterization of an L chondrite impact. Small asteroid 2023 CX1 was detected in space and predicted to impact over Normandy, France, on 13 February 2023. Observations from multiple independent sensors and reduction techniques revealed an unusual but potentially high-risk fragmentation behavior. The nearly spherical 650 $\pm$ 160 kg (72 $\pm$ 6 cm diameter) asteroid catastrophically fragmented around 28 km altitude, releasing 98% of its total energy in a concentrated region of the atmosphere. The resulting shockwave was spherical, not cylindrical, and released more energy closer to the ground. This type of fragmentation increases the risk of significant damage at ground level. These results warrant consideration for a planetary defense strategy for cases where a >3-4 MPa dynamic pressure is expected, including planning for evacuation of areas beneath anticipated disruption locations.

astro-ph.EP↗

arXiv2021

Microtextures in the Chelyabinsk impact breccia reveal the history of Phosphorus-Olivine-Assemblages in chondrites

The geochemistry and textural associations of chondritic phosphate minerals can provide insights into the geological histories of parental asteroids, but the processes governing their formation and deformation remain poorly constrained. Here, we present a quantitative assessment of phosphorus-bearing mineral textures in the three variously-shocked lithologies (light, dark, and melt) of the Chelyabinsk (LL5) ordinary chondrite using scanning electron microscope, electron microprobe, cathodoluminescence, and electron backscatter diffraction techniques. Phase associations, microtextures, and microstructures of phosphates are extremely variable within and between the differently-shocked lithologies investigated in the Chelyabinsk meteorite. We observe continuously strained as well as recrystallized, strain-free phosphate populations. Recrystallized grains (with strain-free subdomains) are present only in the more intensely shocked dark lithology, indicating that phosphate growth in Chelyabinsk predates the development of primary shock-metamorphic textures. This disruption event is also recorded by complete melting of portions of the meteorite to produce the shock-melt lithology, which contains a population of phosphorus-rich olivine grains. We interpret the textures and phase associations of Chelyabinsk to have resulted from initial phosphate growth via metasomatic olivine replacement, followed by major deformation during an early shock-melting impact and a subsequent minor shock event. This minor event appears to have generated a sub-population of phosphates that display patchy CL textures, in both the light and dark lithology. Finally, we propose a new classification scheme to describe various types of Phosphorus-Olivine-Assemblages (Type I-III POAs), which can be used to classify shock metamorphic events and define the associated physicochemical processes.

astro-ph.EP↗