An international team, involving nearly one hundred researchers worldwide, analysed the origin and properties of the asteroid 2023 CX1, detected on 12 February 2023, seven hours before it entered Earth's atmosphere and impacted the French region of Normandy. The results, published in the journal Nature Astronomy in which the Institute of Space Sciences (ICE-CSIC) participates, represent the first comprehensive tracking of an asteroid from space to its impact on Earth.
The asteroid 2023 CX1 struck over Normandy (France) on February 13th at 02:59 UTC. Nearly spherical, it measured just under one meter in diameter with an estimated mass of about 650 kg. It caused a catastrophic disruption at an altitude of about 28 km, releasing 98% of its kinetic energy in a fraction of a second — “an exceptional behaviour for an object of this size”. The explosion scattered more than a hundred fragments across Normandy. The recovered meteorite, named Saint-Pierre-Le Viger (SPLV), is the only ordinary chondrite ever studied from space to laboratory.
The collaboration, led by the Fireball Recovery and Interplanetary Observation Network (FRIPON), the Montreal Planetarium and the University of Western Ontario, confirms the existence of a new population of asteroids linked to L-type chondrites, capable of fragmenting abruptly in the atmosphere and releasing almost all their energy at once. “Such asteroids must be accounted for in planetary defense strategies, as they pose an increased risk to populated areas,” explains Auriane Egal, astrophysicist at the Montreal Planetarium, member of the FRIPON/Vigie-Ciel network, and first author of the study.
Implications for planetary defense
While identified as an ordinary L-type chondrite, the most common class among meteorites on Earth, 2023 CX1 is the only imminent impactor of this kind. In addition, SPLV is the meteorite with one of the most precisely measured orbits to date, since the difference between the predicted and observed atmospheric trajectory was less than 20 meters.
Analyses show that 2023 CX1 separated from its parent body in the inner main belt about 30 million years ago. It experienced an atypical fragmentation, as withstanding high dynamic pressures (4 MPa), the asteroid disintegrated abruptly around 28 km altitude, generating a concentrated spherical shock wave. Hydrodynamic simulations reveal that this type of fragmentation could cause greater ground damage than progressive fragmentations, as observed for the 2013 Chelyabinsk event.
This study highlights the need to integrate spectral, structural, and dynamical characterization of pre-impact asteroids into planetary defence protocols. “L-type chondrite-related asteroids, originating from the inner main belt, may require reinforced alert systems and adapted evacuation plans in the event of a threat”, researchers say.
“This study brings good news because we are in the condition of detecting and tracking rocks smaller than one meter in size, with masses lower than one metric tone. We were suspicious that ordinary chondrites in this size were able to produce meteorites, and here is a new proof of it”, says Josep Maria Trigo-Rodríguez, researcher from the ICE-CSIC and the Institute of Space Studies in Catalonia (IEEC). Coauthor of the study and coordinator in Spain of the FRIPON Network, he has participated in the reconstruction of the atmospheric trajectory and the heliocentric orbit of the superbolide produced by the disintegration of the small asteroid and in the analysis of these unique event’s implications in planetary defence.
The study includes observations carried out with the all-sky cameras for the detection of bolides and meteors of the Montsec Observatory (OdM-IEEC), which were able to capture both the superbolide's trail and the asteroid's explosion into the atmosphere. "Thanks to its location and the quality of the Montsec’s sky, the OdM was the only observatory in Catalonia that was able to record the phenomenon, just below the northern horizon. At an estimated distance of about 1,000 km from the superbolide's bright phase, this one represents the most distant optical observation of a bolide to our knowledge," said Kike Herrero, OdM director and co-author of the study.
An unprecedented scientific and citizen mobilization
2023 CX1 is only the 7th asteroid ever detected prior to impact. Thanks to a novel observational strategy, the European Space Agency (ESA) and NASA predicted the time and location of the fall with unprecedented accuracy.
Space agencies and the FRIPON/Vigie-Ciel network mobilized the public to record the asteroid’s atmospheric entry, resulting in the first large-scale “targeted” observation of a meteorite-dropping bolide. It also enabled the rapid recovery of meteorites on the ground, thanks to an exceptional citizen mobilization.
More than 100 scientists and citizen observers across Europe, America, Africa and Australia joined forces to investigate every aspect of this exceptional fall: telescopic discovery, orbital tracking, atmospheric observations through optical, infrasound and seismic data, and geochemical laboratory analyses. This unique alliance between professional and citizen science demonstrates the power of international cooperation when facing rare and critical celestial events.
