Campo del Cielo

A field of small craters in northern Argentina, where more than 100 tonnes of iron fell from the sky about four thousand years ago.

Key facts

Type

Iron, IAB (with silicate inclusions)

Fell or found

Found

Year

1576 (first Spanish record)

Country

Argentina

Mass

well over 100 tonnes recovered

Official name

Campo del Cielo

On the flat plains of the Gran Chaco in northern Argentina lies a stretch of land with a poetic name: Campo del Cielo, the 'Field of the Sky'. The name was no accident. Long before Spanish settlers arrived, the Indigenous peoples of the region knew of great masses of iron lying in the ground and told of metal that had fallen from the heavens. They were right. Campo del Cielo is one of the largest meteorite falls known, a shower of iron that blasted a field of craters and left more than 100 tonnes of metal behind.

Explorers and a lost giant

The first written record dates from 1576, when the Spanish governor of the region sent an expedition, led by Hernán Mexía de Miraval, to investigate reports of a huge mass of metal. The Spanish hoped it might be silver; it was iron. Two centuries later, in 1783, an officer named Miguel Rubín de Celis studied a great mass known as the Mesón de Fierro, the 'iron table', estimated at around 15 tonnes. Puzzlingly, he concluded that it had formed by some natural process on Earth. The Mesón de Fierro has never been found again, and it may still be lying somewhere under the soil. A large mass sent to Britain in the 19th century remains in the collection of the Natural History Museum in London.

A field of craters

Campo del Cielo contains at least 26 small craters scattered along a line roughly 18 kilometres long, the largest about 100 metres across. They formed when a large iron meteoroid broke apart in the atmosphere and its fragments struck the ground together. Charcoal from vegetation burned at the time has allowed scientists to use radiocarbon dating, which measures the decay of a natural radioactive form of carbon, to date the event to roughly 4,000 to 4,500 years ago. People were almost certainly living in the region when it happened.

Monster masses

The field has yielded some of the heaviest single meteorites known. A mass named El Chaco, found deep within one of the craters in 1969, weighs roughly 29 tonnes. In 2016 an even heavier mass, called Gancedo, was excavated and weighed at about 30.8 tonnes, placing it among the very heaviest meteorites on Earth. Thousands of smaller pieces, from tiny fragments to boulders, have been found across the area, many of them by local people.

That popularity has brought problems. In 1990 an attempt to remove El Chaco from Argentina was stopped by the authorities, and the large masses are now protected by provincial law. As always, meteorite hunting must respect local laws and landowners.

What the iron is made of

Campo del Cielo is an iron meteorite of the IAB group. Unlike most irons, which are pure metal from a shattered asteroid core, IAB irons often contain inclusions of rocky silicate minerals and graphite, a form of carbon. Their chemistry suggests they formed in a different way, perhaps in pools of molten metal created by impacts on or near the surface of a partly melted asteroid, rather than in a single deep core. When etched, Campo del Cielo shows a coarse Widmanstätten pattern of broad metal crystals.

Why it matters

Campo del Cielo is a superb natural laboratory. It shows how a single incoming body can fragment and produce a whole cluster of craters, and its huge recovered mass helps scientists estimate the size of the original meteoroid. Its long human history, from Indigenous knowledge to colonial expeditions and modern scientific study, makes it a reminder that people have always noticed, and wondered at, the iron that falls from the sky.

Did you know?

See more

Campo del Cielo in the catalogue