Want to stay on top of all the space news? Follow @universetoday on TwitterCampo del Cielo is the area between the Argentinian provinces of Chaco and Santiago del Estero where a large number of iron meteorites have been found. The area is about 1,000 km northwest of Buenos Aires. The meteor field is 3 km by 20 km and contains at least 26 different impact craters. The largest of which is 115 m by 91 m. The best estimate of the age of the craters is between 4,000 and 5,000 years. The craters were first discovered by Europeans in 1576, but had been known and worshiped by aboriginal Indians for hundred of years before that. The craters and the area around contain many fragments of what is believed to be a single iron meteorite. The total weight of the pieces recovered exceeds 100 tons. That makes the meteorite the heaviest one ever recovered on Earth. The largest fragment, consisting of 37 tons, is the second heaviest single-piece meteorite recovered on Earth, after the Hoba meteorite.
Campo del Cielo was found by the Spanish in 1576. The governor of the local province sent men to look for it after hearing that it was the place where the natives found the iron that they used in their weapons. Whether he wanted to deprive the Indians of their source or needed iron for his soldiers weaponry is unknown. The expedition found a large mass of metal protruding out of the soil. They assumed it was an iron mine and brought back a few samples, which were described as being of unusual purity. The governor documented the expedition in Seville. The report was quickly forgotten as were many reports from functionaries of the time. There were two additional ventures to Camp del Cielo. In 1774, Don Bartolome Francisco de Maguna rediscovered the iron mass which he called “the Table of Iron”. Maguna thought the mass was the tip of an iron vein. The next expedition, led by Rubin de Celis in 1783, used explosives to clear the ground around the mass and found that it was probably a single stone. Celis estimated its mass as 15 tons and abandoned it as worthless. He himself did not believe that the stone had fallen from the sky and assumed that it had formed by a volcanic eruption. However, he sent the samples to the Royal Society of London. Those samples were later analyzed and found to contain 90% iron and 10% nickel and other trace elements and was assigned to a meteoric origin. The use of the meteorites for weapons and the blasting make it impossible to know the exact size of the original meteorite.
The Campo del Cielo crater field contains at least 26 craters, as I said earlier. At least two of the craters contained thousands of small iron pieces. Such an unusual distribution suggests that a large body entered the Earth’s atmosphere and broke into pieces which fell to the ground. The size of the main body is estimated as larger than 4 meters in diameter. The fragments contain an unusually high density of inclusions for an iron meteorite, which might have facilitated the disintegration of the original meteorite. Samples of charred wood were taken from beneath the meteorite fragments and analyzed for carbon-14 composition. The results indicate the date of meteorite to be between 4,200 and 4,700 years ago, which would be about 2,200–2,700 years B.C. The average composition of the Campo del Cielo meteorites is 6.67% Ni, 0.43% Co, 0.25% P, 87 ppm Ga, 407 ppm Ge, and 3.6 ppm Ir, with the rest being iron.
Campo del Cielo is an awesome impact event. Here on Universe Today we have a great article about the 10 most impressive craters on Earth. Here is an article about Campo del Cielo. Astronomy Cast offers a good episode about craters that is very detailed.