An international collaboration has published the first complete characterisation of an asteroid (2023CX1), from its detection to the analysis of meteorites found on the ground. This study refines Earth alert and defence protocols and shows that certain types of small asteroids may pose an increased risk to inhabited areas.
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iscovered seven hours before entering our atmosphere, 2023CX1 exploded over Normandy on 13 February 2023 at 02:59 UTC (Coordinated Universal Time, a common reference for all clocks), releasing 98% of its energy in a fraction of a second. The FRIPON/Vigie-Ciel* network and an unprecedented citizen mobilisation enabled the first "targeted" observation of a fireball and the rapid recovery of fragments.
Led by Auriane Égal, around a hundred researchers have produced the first comprehensive study of an asteroid tracked from the sky to the ground. 2023 CX1, which is almost spherical (≈ 1 m, ~ 650 kg), was detected on 12 February 2023; its time and place of entry were calculated with record accuracy. At an altitude of approximately 28 km, its sudden disintegration released almost all of its energy at once, scattering more than a hundred fragments across Normandy. The meteorite (fragments of the asteroid that entered the atmosphere) - named Saint-Pierre-Le-Viger (SPLV) - became the only ordinary chondrite ever studied both from space and in the laboratory.
The FRIPON/Vigie-Ciel network - of which Emmanuel Jehin, an astronomer at the University of Liège, is a member - orchestrated the first targeted observation of a meteorite re-entry, mobilising observatories and the public to film the fireball and speed up the search for meteorites. Thanks to these efforts, the group was able to calculate the orbit with unparalleled accuracy (a difference of less than 20 metres between the predicted and observed trajectories) and a physical fragmentation model useful for emergency planning.
Interest for planetary defence
The study confirms an 'all-or-nothing' fragmentation below approximately 4 MPa of dynamic pressure, which is a signature that can increase ground damage compared to gradual disintegration (such as in Chelyabinsk). It argues for the integration of spectral signature, structure and dynamics of objects detected before impact into alert and evacuation protocols.
Emmanuel Jehin, a member of the FRIPON team and involved in planetary defence at ULiège, highlights the role of observation resources - including the TRAPPIST telescope network and the FRIPON camera installed on the roof of the Institute of Astrophysics - in this success: "This study shows the remarkable progress made in planetary defence in recent years, as it was possible, thanks to the increase in observation resources, to detect this tiny asteroid (only 1 m in diameter) in space, to characterise it with ground-based telescopes (size and composition), calculate its precise trajectory in record time using supercomputers, determine with great accuracy the location and time of entry into the atmosphere, and even recover the associated meteorites on the ground! Their study has made it possible to further refine the stony nature of this small asteroid. However, there is still a huge amount of work to be done to detect them all in time, but this is a very important test case demonstrating the feasibility of the warning chain.
Earlier alerts, better decisions, and more accurate evacuations: 2023 CX1 demonstrates that a complete chain - from telescopes to simulators to meteorite hunters - can be operational in a matter of hours. For the public, this means more reliable warning messages and localised instructions; for the authorities, it means key physical parameters (ultra-precise orbit, fragmentation mode, energy deposited) in order to adapt emergency plans to "small" impactors. A scientific breakthrough that translates into safety.
On February 12, 2023, a small asteroid was detected in space 6.7 hours before colliding with Earth. Thanks to exceptional public mobilization, many records of the asteroid's atmospheric entry were captured across Europe, enabling one of the fastest meteorite recoveries in history.
Fall and recovery of asteroid 2023 CX1
* FRIPON (Fireball Recovery and InterPlanetary Observation Network) is an automated network of cameras (and radio receivers) deployed mainly in Europe to detect "fireballs", calculate their trajectory/orbit and guide the recovery of freshly fallen meteorites. In France, it also relies on the Vigie-Ciel participatory science programme. The network has ~150 cameras and ~25 radio stations, covering ~1.5 million km².
Egal, A., Vida, D., Colas, F. et al. Catastrophic disruption of asteroid 2023 CX1 and implications for planetary defence. Nat Astron (2025). https://doi.org/10.1038/s41550-025-02659-8
Emmanuel Jehin
