A large international collaboration of nearly 100 researchers, led by Western adjunct professor Auriane Egal, has completed the first-ever comprehensive study of an asteroid tracked from space through to its impact on Earth. The analysis of asteroid 2023 CX1 represents a unique opportunity for both science and planetary defence.
The asteroid, quite ordinary by space rock standards, exploded so quickly and with so much force that its actions underscore the potential threat of similar - albeit larger - astronomical objects.
The findings were published Sept. 17 in the high impact journal Nature Astronomy.
Discovered on Feb. 12, 2023, barely seven hours before entering Earth's atmosphere, 2023 CX1 struck over Normandy, France, on February 13 at 2:59am GMT. Nearly spherical, it measured just under one metre in diameter with an estimated mass of about 650 kg. When it abruptly shattered just 28 kilometres above Earth, it released 98 per cent of its 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 L-type chondrite (a type of stony meteorite) ever studied from space to laboratory.
Using new and innovative observational strategies, ESA and NASA successfully predicted the time and location of 2023 CX1's fall with unprecedented accuracy. The difference between the predicted and observed atmospheric trajectory was less than 20 meters, making SPLV the meteorite with one of the most precisely measured orbits to date.
The 94g meteorite found by citizen scientist Loïs Leblanc (Marie-Lan Taÿ Pamart)
The space agencies and FRIPON/Vigie-Ciel, a France-based camera network used to track incoming meteoroids, mobilized the public to record the asteroid's atmospheric entry, resulting in the first large-scale targeted observation of a meteor. It also enabled the rapid recovery of meteorites on the ground, samples which were later studied in a laboratory to complete the comprehensive study.
More than 100 scientists, including meteor physicists from Western Space, 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 scientists demonstrates the power of international cooperation when facing rare and critical celestial events," said Egal, an astrophysicist and scientific advisor at the Montreal Planétarium and lead author of the study.
Denis Vida (Western Science)
The Western-led Global Meteor Network, founded by Western adjunct physics and astronomy professor Denis Vida, was critical in collecting data required for predicting the fall zone for 2023 CX1. Physics and astronomy professor Peter Brown and former graduate student Luke McFadden also contributed to the analysis of the event's acoustic signals, and physics and astronomy professor Paul Wiegert was involved in reverse engineering the asteroid's time in flight prior to impact.
"This is the first time we have telescopic observation of an asteroid before it entered the atmosphere. We tracked it as it entered our space, and we correctly predicted the impact location by calculating its orbit and size," said Vida, a study co-author. "From first observation to final impact and recovery, the whole clockwork of planetary defence worked really well."
Risk and reward
Analyses of 2023 CX1 - only the seventh asteroid ever detected prior to impact - showed it separated from its parent body in the inner part of the asteroid belt, located between Mars and Jupiter, about 30 million years ago.
Computer simulations constructed after 2023 CX1's recovery revealed this type of fragmentation could cause greater ground damage than typical fragmentations, like those observed for the 2013 Chelyabinsk, Russia meteor event - the largest known natural object to have entered Earth's atmosphere since the 1908 Tunguska event in Siberia.
This study highlights the need to integrate observation and analysis of pre-impact asteroids into planetary defence protocols. L-type chondrite-related asteroids, like 2023 CX1, may require reinforced alert systems and adapted evacuation plans in the event of a threat.
"We confirmed 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 defence strategies, as they pose an increased risk to populated areas," said Egal.
