Campo del Cielo

Campo del Cielo, translating to "Field of Heaven" or "Field of the Sky," is a renowned impact structure located in Argentina, distinguished by its extensive crater field and the immense quantity of iron meteorite fragments recovered from its vicinity. This significant site spans the provinces of Chaco and Santiago del Estero, situated approximately 1,000 kilometers north-northwest of Buenos Aires.

Discovery and History

The existence of the iron masses at Campo del Cielo was first formally reported to the public in 1576. A Spanish governor commissioned a military expedition to investigate reports from the indigenous peoples about a mass of iron that had fallen from the sky. This expedition located a large metallic mass protruding from the ground, and initial samples were collected. While the governor's report was filed, its details were largely forgotten, and subsequent accounts relied on local legends.

Later rediscoveries occurred in the 18th century. In 1774, Don Bartolomé Francisco de Maguna identified the iron mass, calling it "el Mesón de Fierro" (the Table of Iron), initially believing it to be part of an iron vein. An expedition in 1783 led by Rubin de Celis attempted to excavate the mass, using explosives. While this revealed it to be a single stone, Celis incorrectly attributed its formation to a volcanic eruption and estimated its mass at 15 tonnes. However, samples sent to the Royal Society in London were analyzed and confirmed to be of meteoritic origin, containing approximately 90% iron and 10% nickel.

Since these early investigations, hundreds of iron pieces, ranging from tiny fragments to several tonnes, have been unearthed. Notable large fragments include the Otumpa (approximately 1 tonne), El Taco, the 28.8-tonne El Chaco (discovered in 1969 and extracted in 1980), and the 30.8-tonne Gancedo meteorite (unearthed in 2016). As of recent discoveries, over 100 tonnes of Campo del Cielo fragments have been found, making it the most substantial collection of meteorite material recovered from a single impact event on Earth.

The Impact Event and Craters

The Campo del Cielo impact event created a field of at least 26 distinct craters, spread across an area of 18.5 by 3 kilometers, with a wider strewn field for smaller fragments extending an additional 60 kilometers. The largest crater measures approximately 115 by 91 meters. Scientific analysis, including carbon-14 dating of charred wood found beneath meteorite fragments, suggests the impact occurred roughly 4,000 to 5,000 years ago (or 2,200–2,700 years BC). The original celestial body that caused these impacts is estimated to have been an iron meteorite larger than 4 meters in diameter.

The composition of the recovered fragments is primarily iron, with notable percentages of nickel, cobalt, and phosphorus, along with trace amounts of iridium, gallium, and germanium. The high density of inclusions within these iron meteorites may have contributed to the fragmentation of the original body upon atmospheric entry and impact.