The L'Aigle Meteorite Shower And The Birth of Meteoritics

Jan 17, 2024 0 comments

Prior to the 1800s, scientists were skeptical about the existence of meteorites. Despite historical reports of meteorite sightings dating back to Roman times, the idea of rocks falling from the heavens seemed implausible to scientists of that era. The prevailing belief was that meteorites were of terrestrial origin, possibly originating from volcanic activity or, as suggested by René Descartes in the 17th century, formed by the fusion of atmospheric dust particles due to lightning.

A meteor shower in 1783. Image credit: Wellcome Collection

In 1794, the German physicist Ernst Chladni challenged this view by proposing in a book that meteorites are extraterrestrial in origin. Chladni suggested that these celestial bodies were fragments scattered throughout the solar system that never coalesced into planets. He argued that this explanation could account for the high velocities of the falling masses, resulting in their intense brightness upon entering Earth's atmosphere. Chladni also pointed out the correlation between reported fireballs and instances of stones falling, along with the physical similarities observed in the recovered rocks from these falls.

Chladni's hypothesis faced considerable controversy during its time, as it contradicted the views held by both Isaac Newton and Aristotle regarding celestial bodies. Moreover, his assertions challenged the prevailing belief that beyond the Moon, there existed nothing but stars and planets. Despite these challenges, Chladni's book sparked debate among scientists. While some embraced his extraterrestrial origin theory for meteorites, others staunchly rejected it, favoring alternative explanations involving volcanic activities, turbulent ocean currents, or the formation through lightning striking iron ore.

Ernst Chladni

Several years following the publication of Chladni's work, astronomers began making groundbreaking discoveries that added weight to the idea of extraterrestrial objects in the solar system. In 1801, Giuseppe Piazzi identified Ceres, marking the first detection of what we now recognize as asteroids. Heinrich Olbers continued this trend in 1802 by discovering Pallas. Concurrently, in 1802, chemists Jacques-Luis de Bournon and Edward C. Howard delved into the analysis of meteorites, revealing distinct chemical compositions and mineral contents that set them apart from terrestrial rocks. These emerging findings gradually lent support to the notion that meteorites were indeed extraterrestrial in origin.

In the early afternoon of April 26, 1803, the town of L'Aigle in Normandy, France, experienced an extraordinary event as over 3,000 meteorite fragments showered down. The French Academy of Sciences promptly dispatched the young scientist Jean-Baptiste Biot to investigate this celestial occurrence. Through meticulous fieldwork, Biot gathered diverse eyewitness testimonies and analyzed stone samples from the vicinity, ultimately presenting compelling evidence supporting an extraterrestrial origin for the fallen stones.

Jean Baptiste Biot

Firstly, Biot noted that the composition of the stones differed significantly from any local materials, yet bore striking similarities to stones previously documented from celestial falls in other locations. This observation suggested a common extraterrestrial source for these stones. Biot emphasized, “The foundries, the factories, the mines of the surroundings I have visited, have nothing in their products, nor in their slag that have with these substances any relation. No trace of a volcano, can be seen in the region.”

Secondly, Biot reported to have interviewed many witnesses who independently attested to observing a "rain of stones thrown by the meteor." These witnesses came from various backgrounds, and Biot argued that it would be implausible to believe that they had collaborated to fabricate a description of an event that did not occur. This combination of geological evidence and diverse eyewitness accounts provided strong support for the idea that meteorites indeed had an extraterrestrial origin.

The L'Aigle meteorite. Photo credit: Marie-Lan Taÿ Pamart/Wikimedia Commons

Biot's impassioned paper, unequivocally asserting the extraterrestrial origin of the stones from the L'Aigle meteorite shower, marked the inception of the science of meteoritics. A mere month after Biot's report, Professor Prevost declared, “Few facts are more established in physics than the fall of meteoritic stones. And within a few months, we moved from doubt to certainty. The report of C. Biot on the meteor of Florral 6th an XI and on the fall of stones that happened at the north of L'Aigle leaves nothing to be desired in that respect.”

Today, the L'Aigle meteorite, alongside Angers, another meteorite that struck France 19 years later, is preserved in a dedicated room at the Muséum d'histoire naturelle d'Angers, a French natural history museum. These meteorites stand as tangible reminders of a pivotal moment in the history of science, where skepticism gave way to acceptance, and the study of meteoritics emerged as a legitimate field of inquiry.

# Matthieu Gounelle, The meteorite fall at L’Aigle and the Biot report: exploring the cradle of meteoritics, Geological Society, London, Special Publications
# L’Aigle Meteorite Fall of 1803, American Astronomical Society


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