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When Benjamin Silliman and James Kingsley from Yale reported stones falling from the sky over Weston, Connecticut, Thomas Jefferson, child of the Enlightenment that he was, is reported to have said, "It is easier to believe that two Yankee professors would lie than that stones would fall from heaven." It is therefore ironic that nearly 200 years later, convincing evidence has been amassed in Chesapeake Invader by C. Wylie Poag, a paleontologist from the U.S. Geological Survey in Woods Hole, Massachusetts, that a vastly larger meteor impacted south of the Mason-Dixon line, creating a 100-kilometer-wide crater that lies deeply buried under Chesapeake Bay and the shores of Jefferson's Virginia.
Jefferson's Humean skepticism about meteorites was not directed just at New England and it was not expressed out of scientific ignorance. He had published several geologic contributions, and he was aware of some details of the then-current scientific controversy over stones falling from the sky. For many skeptics the first convincing investigation had come a few years earlier, in 1803, when Jean-Baptiste Biot, a brilliant young professor of the College de France and friend of Laplace, was dispatched by the French Academy of Sciences to investigate a fall of stones near the town of L'Aigle in Normandy. He collected detailed testimony from the surrounding villages that confirmed the time and place of the fall, that about 3000 stones fell in a 4-by-10-kilometer area, and that the stones were found lying on top of the ground and were of a type unlike rocks native to the area.
Biot's evidence was overwhelmingly convincing—but not to Jefferson, who wrote to a friend saying that the report was a result of "the exuberant imagination of a Frenchman … run away with his judgment. The evidence of nature, derived from experience, must be put into one scale, and in the other the testimony of man, his ignorance, the deception of his senses, his lying disposition."
Nevertheless, evidence has gradually accumulated in support of stones falling from the sky, with more than a thousand such events documented and over 10,000 meteorites catalogued in collections. Irons are of course the epitome of meteorites and obviously come from somewhere else. But they are the exception, only a few percent of all meteorites. The vast majority are stony and don't look that different from Earth rocks to an inexperienced eye. But stony meteorites are in fact utterly unearthly. They are Rosetta stones recording the primeval history of the Solar System and before.
Most stony meteorites are like agglutinations of tiny hailstones—not composed of ice, but of dense silicate spherules—with an overall chemical composition nearly identical to that of the Sun, minus its more gaseous components such as hydrogen and helium. Evidence has gradually accumulated that these meteorites are the original condensations of the solar nebula from which our sun and planets formed. They are all primeval, consistently showing evidence that nearly nothing has happened to them in the last 4.5 billion years. They are the odd fragments left over from the assembly of the Solar System and the formation of its planets.
Claude Allegre, a brilliant geochemist at the University of Paris and the politically controversial Minister of Science and Education in the current French government, tells this fascinating story of meteorites and the origin and early history of the Solar System in his outstanding classic, From Stone to Star. A major gap exists in the historical record between the primeval meteorites and the oldest remaining rocks of the geologic record on Earth. However, the tectonically dead planets preserve a record of this early era and show that it was a time of intense bombardment of asteroids and their smaller fragments, the meteorites, saturating the surfaces of the Moon, Mercury, and parts of Mars with a no man's land of craters on top of craters.
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