arXiv subjects

Simon Anghel

Publications and source records attributed to Simon Anghel.

3 recordsLinked to original sources

arXiv2026

Meteor clusters: tracing meteoroid fragmentation in near-Earth space

Meteor clusters are typically defined as groups of meteors that appear close together in both space and time. To date, only a handful of such events have been recorded instrumentally and analysed in detail. In many documented cases, thermal stress has been identified as the most likely cause of meteoroid fragmentation near Earth. This paper documents two further cases and provides a summary of all currently known clusters. The two clusters that were recorded over Hawaii Island in 2023 and 2024 represent two distinct scenarios. The 2024 meteor cluster was characterised by a dominant mass body and, with the fragments arranged along the antisolar direction according to their mass. Such cases enable us to reliably determine the age of the cluster and identify the most likely formation scenario. This cluster was around three days old, and the thermal stress was the most likely mechanism of its formation. The 2023 cluster was not such a case. It does not contain a mass dominant body, nor are its fragments arranged by their mass. Therefore, it was only possible to estimate its age to be no more than four days. Furthermore, other potential formation mechanisms besides thermal stress cannot be ruled out. This fact was observed in all analysed clusters. All clusters known up to date were formed in close proximity to Earth. The volume of a cluster increases with its age. This means that older clusters, formed by the fragmentation far away from Earth may remain undetected, as their fragments are also dispersed too widely to be observed by local experiment. However, global networks can detect such dispersed clusters.

astro-ph.EP↗

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↗

arXiv2025

Perihelion history and atmospheric survival as primary drivers of the Earth`s meteorite record

Models predict that more than half of all impacting meteoroids should be carbonaceous, reflecting the abundance of carbon-rich asteroids in the main belt and near-Earth space. Yet carbonaceous chondrites represent only about 4% of meteorites recovered worldwide. Here we analyse 7,982 meteoroid impacts and 540 potential meteorite falls from 19 global observation networks and demonstrate that intense thermal stress at low perihelion distances coupled with the filtering effect of Earth`s atmosphere explains this mismatch. Meteoroids repeatedly subjected to intense thermal cycling near the Sun fracture and weaken, removing the most friable objects even before atmospheric entry. Our data also show that tidally disrupted meteoroid streams produce especially fragile fragments that rarely survive to the ground. Consequently, compact, higher-strength, thermally cycled bodies dominate the meteorite record. These findings reconcile the predicted carbonaceous flux with its scarcity in collections, underscoring how orbital evolution and atmospheric filtering shape the materials that reach Earth`s surface.

astro-ph.EP↗