Some small asteroids can explode suddenly

Some asteroids are more dangerous than others, according to a report published in Natural astronomy By an international team of researchers, led by the Auriane Egal astrophysics of the Montreal Planetarium in Canada. The team had presented its conclusions of an investigation into the impact of small asteroids 2023 CX1 in France in February 2023. This new article revealed that small asteroids can explode on atmospheric entrance.

“The asteroid was discovered in space for about seven hours before entering the earth’s atmosphere on Normandy,” said astronomer and principal author Peter Jenniskens of Seti Institute and Nasa Ames Research Center. “I immediately phoned my brother in the Netherlands, who came out and saw the fire ball.”

Other observers have been alerted to the imminent impact and the spectacular images and videos recorded from the resulting meteor.

“Our team determined that the asteroid was almost spherical and measured about 72 centimeters in diameter, a little under a courtyard,” said Egal. “He had an estimated mass at around 650 kg.”

These photographic and video data revealed that the calculated asteroid orbit was slightly deactivated because all observatories did not report their elevation in the same geodetic framework. It has since been corrected.

“It was the third impact announced on the earth,” said Jenniskens, who had previously guided the resumption of the first two impacts of the 2008 TC3 asteroids in Sudan and in 2018 in Botswana.

For this fall, Jenniskens joined forces with the astronomer François Colas of the Paris Observatory, the head of the Fripon Fireball Camera Network. They guided a team of Volunteers from Fripon / Vigie-Ciel to their first discovery a few hours after their arrival in the small town of Saint-Pierre-le-Viger in Normandy.

“This recovery was difficult because of the strong winds that blew up meteorites,” said Jenniskens. “The atmosphere tends to sort the stones by mass, but the first stone found was much heavier than what I expected, so we still did not know where the central line of the spared field was.”

After having scanned the area systematically with a group of around 12 fripon / watchders researchers, Jenniskens himself found the second meteorite, a small mass of 3 grams, late the next day, a meteorite which is now at the Museum of Natural History in Paris.

“The meteorite was so small that it only distinguished itself because the rock was seated on the foam in the short grass,” said Jenniskens. “With a large stone at one end and a small stone on the other, this find established the location of the scattered field.”

Analysis has shown that the meteorite was a common type – the most frequently decreased and the most restored on Earth – ordinary chondritis of the low iron content.

“These types are also common among the biggest asteroid impacts,” said Jenniskens. “What made this impact unusual is the double shiny rocket towards the end of the fire ball.”

The team concluded that this particular asteroid gathered well until deeper in the atmosphere, where it has lost 98% of its kinetic energy in a fraction of a second.

“The asteroid has suddenly disintegrated around 28 km altitude, generating a concentrated spherical shock wave,” said EGAL.

The calculations carried out at the NASA Ames Research Center by the co-author Darrel Robertson showed that the area affected by high overpressures was four times greater than for a typical asteroid impact, where energy is released over a longer distance, starting more in the atmosphere. The closer the explosion, the more these differences will be pronounced.

“Our team has confirmed the existence of a new asteroid population linked to type L chondrites, capable of suddenly fragment into the atmosphere and to release almost all their energy at the same time,” said Egal. “Such asteroids must be taken into account in planetary defense strategies, as they have an increased risk for populated areas.”