Carancas

In 2007 a stony meteorite blasted a crater near Lake Titicaca – something scientists had not expected a rock its size to do.

Key facts

Type

Ordinary chondrite (H4–5)

Fell or found

Fell (witnessed)

Year

2007 (15 September)

Country

Peru

Mass

impactor probably a few tonnes; fragments recovered

Official name

Carancas

Late in the morning of 15 September 2007, people near the village of Carancas, in the high plains close to Lake Titicaca in southern Peru, saw a bright fireball trailing smoke and heard a tremendous explosion. When they ran to look, they found a fresh crater about 13 to 14 metres across, steaming and quickly filling with groundwater. Mud and rock had been thrown out across the surrounding fields.

A crater that should not exist

Carancas surprised scientists because the meteorite was a stony one, an ordinary chondrite. Most stony meteoroids of modest size are expected to break apart high in the atmosphere, with their fragments slowed by air resistance until they fall gently enough to land without making a crater. Craters are usually made by iron meteorites, which are stronger, or by much larger stony bodies.

Yet at Carancas, a stony meteoroid only a metre or two across appears to have reached the ground largely intact, at a speed of a few kilometres per second, fast enough to blast out a crater. Researchers suggested that it may have stayed together because of its relatively strong structure, and that the high altitude of the site, about 3,800 metres above sea level, meant it passed through less atmosphere before striking the ground. Its story has made scientists rethink how small stony bodies can behave.

Mystery illness

After the impact, some local residents and police reported headaches, nausea and other symptoms. This caused alarm and wild speculation in the media, including fears of radiation or unknown substances. Investigations found no evidence of radiation. A likely explanation is that the impact heated groundwater containing natural arsenic and other compounds, releasing fumes, though stress and fear may also have played a part. The symptoms were short-lived.

What it is

Fragments collected from the crater and the surrounding area show that the Carancas meteorite is an H4–5 ordinary chondrite. 'H' means high iron: these meteorites contain flecks of iron-nickel metal and attract a magnet. The numbers 4 and 5 describe how much the rock was heated inside its parent asteroid. Most of the meteoroid shattered on impact, and the fragments recovered are mostly small.

A rare modern crater

Carancas is one of the very few impact craters ever seen to form. Most of Earth's craters are thousands to millions of years old, and only a handful, such as the Sikhote-Alin craters of 1947, have formed in recorded history. Rain and wind began softening the Carancas crater's shape almost at once, a reminder of how quickly small craters disappear on an active planet like Earth. At Carancas, scientists could study a fresh crater within days, examining how its rim and ejecta formed, how far debris was thrown, and how the ground responded. The site also became a source of interest for local people and tourists. Many villagers visited the crater and some took fragments before scientists arrived. Peruvian geologists studied the site soon afterwards, and their measurements, together with fragments collected nearby, allowed researchers to piece together what had happened.

Why it matters

Carancas teaches an important lesson about planetary defence: small stony objects do not always break up harmlessly. Scientists use events like this to improve computer models of how meteoroids enter the atmosphere and when they might reach the ground.

It also shows the importance of calm, careful investigation. Early reports were full of rumours, but scientific study explained what had happened. If you ever witness a meteorite fall, report it, avoid touching or tasting any material, keep away from fresh crater water or fumes, and let experts investigate. Remember too that local laws and landowners' rights apply to any meteorite fragments that are found.

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Carancas in the catalogueCarancas crater