During the Middle Ages, the official position of the Roman Catholic Church was this: Meteorites do not exist. The Firmament—the argument went—was created by God and therefore perfect. To suggest stones fell from the sky was to suggest that God was imperfect. All of that changed on April 26, 1803 when literally thousands of stone meteorites rained down over the French village of L'Aigle ("The Eagle") in Normandy. So many people witnessed the event that the existence of meteorites could no longer be debated. Scientist Jean-Baptiste Biot was dispatched to investigate and the specimens that he collected can still be seen in meteorite collections around the world. The L'Aigle fall is viewed by many not only as the birth of meteoritics, but also as a triumph of science over superstition. STEVE:
After crossing the giant hurdle of accepting that rocks do fall from the sky, science then had the huge task of determining things such as: Why do they fall from the sky? Where do they come from? How did they form? What else can they tell us about the universe? A little over 200 years after the fall at L'Aigle, we have answered many of those original questions, but as is true with so many areas of science, one answer often leads to more questions that need to be answered.
GEOFF: On February 15, 2013, morning skies over the Russian city of Chelyabinsk were illuminated by an enormous fireball. Traveling at 41,000 mph, it could be seen from over a hundred miles away. While not nearly the largest meteorite fall known, it scores two firsts in recorded history: (1) Never before had serious damage been inflicted upon a city by meteorites; (2) Over 1,500 people were injured, not by the falling meteorites, but by broken glass and other debris resulting from the incoming meteorite's shockwave. In addition, and thanks to the popularity of in-car video cameras in Russia, there is more footage of this fireball than all other fireballs in history put together. Chelyabinsk was a wake-up call for the world, and alerted us to the very real dangers posed by large meteorites.
STEVE: It seems that over the past few years there have been more fireballs seen than ever before. I believe, however, that it is more a case of news agencies discovering that stories about fireballs and meteorites are newsworthy events that generate click-throughs on their websites. As a result, meteorite-related stories are being published more and more frequently. While most fireballs are reported locally or regionally, Chelyabinsk was reported on a global scale and it shook the whole world! Had the falling asteroid fragment on that fateful morning been composed of iron (as 4% of meteorite falls are) it would have been a crater-forming event generating a kill zone in the neighborhood of 5 km in diameter.
3 Canyon Diablo
The iron meteorite that formed Arizona's magnificent Meteor Crater, some 50,000 years ago, is called Canyon Diablo. In 1902, Daniel Moreau Barringer, a geologist and mining engineer, first visited the curious geological feature known as Coon Mountain, between Flagstaff and Winslow in northern Arizona. Convinced that the 4,000-ft wide, bowl-shaped depression had been formed by a giant meteorite, Barringer spent much of the rest of his life, and much of his fortune, investigating and mining at the site now known as Meteor Crater. In later years, it would become the first proven meteorite impact crater on Earth. Seminal meteorite researcher H.H. Nininger did much of his groundbreaking work there; meteoric iron from the site was melted down and used for fabrication and construction during wartime; Apollo astronauts trained at Meteor Crater during the 1960s; and the very large number of specimens found over the past 100-plus years makes Canyon Diablo one of the most widely available and widely studied meteorites in history. Meteor Crater is open to visitors year-round. STEVE:
Canyon Diablo and the crater it formed are, between them, the perfect poster child for meteorites—literally. More posters, postcards and photos in general of Meteor Crater have been distributed around the globe than for any other meteorite-related site. When space and the Earth collide, this is what happens. Everyone on the planet should take note!
Carbonaceous chondrites are ancient and fascinating meteorites. Some contain water and carbon compounds and some specialists believe they may have been instrumental in bringing the materials necessary for life to Earth. Some contain micro diamonds that are believed be 12 billion years old and pre-date our own solar system! At approximately 1 a.m. on the night of February 8, 1969 a massive carbonaceous body entered our atmosphere and broke up over the town of Allende in Chihuahua, Mexico. Dr. Elbert King, a NASA scientist working in Houston, heard about the fall and traveled immediately to the site. He found and purchased numerous examples and returned with them to the United States. He then proceeded to exchange specimens with researchers around the world, making this exceedingly rare and scientifically valuable material available to his international colleagues. As such, Allende is often described as "the best-studied meteorite in history" and has provided us with clues about the birth of our solar system and, perhaps, the birth of life itself. STEVE:
The Meteoritical Society is an international body of scientists who study meteorites. Their annual meeting is held in a different city each year. In a cosmic coincidence, their 1969 AGM happened to take place in Houston at the Manned Spacecraft Center (later renamed Johnson Space Center). Dr. King allowed his large collection of Allende meteorites to serve as practice specimens for NASA's newly-constructed Lunar Receiving Laboratory. The LRL's equipment, existing in the most sterile environment on the planet, used Allende as test samples prior to examining moon rocks returned to Earth by the Apollo crews.
Beneath the Yucatan Peninsula in Mexico lie the remains of an ancient meteorite crater of staggering size: 110 miles in diameter and an estimated 66 million years old. Physicist and geologist, father-and-son-team Luis and Walter Alvarez theorized that the Chicxulub meteorite impact may have caused the extinction of the dinosaurs. To this day, a thin layer of fallout from the cataclysmic event can be found around the world at a geological stratum known as the K/T boundary. Whether or not it was directly responsible for the demise of the dinosaurs, the Chicxulub impact undoubtedly caused global devastation and may have influenced the very course of evolution on Earth. STEVE:
It has happened before many times, and it will happen again—sometime. Every year there is less stray material wandering around our solar system as cosmic debris gets swept up when asteroid fragments slam into planets or get pulled into the Sun. And yet there are still planet-killer bodies roaming around out there, not to mention the occasional comet that comes out of nowhere to pay our inner solar system a visit. The 66 million-year-old Chicxulub impactor event, and the fossils from that period, are reminders to us that, in life, there are some things we just can't change. We either adapt or become extinct. Let's hope the next big one happens a few hundred million years from now!
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