The case of the Peruvian meteorite

ONE OF THE MOST ATYPICAL FALLS ON RECORD: THE CASE OF THE PERUVIAN METEORITE

At 11:45 in the morning of Saturday, 15 September 2007, the residents of the village of Carancas, Peru, heard alarmed a rumbling noise. Numerous witnesses observed a bright object in the sky, flaming, which was descending until it impacted the ground, causing an explosion that left pieces of calcined material scattered throughout the area.

Mrs. Justina Limache, 74 years old, told Carlos Fernández Baca from the newspaper El Comercio, that she abandoned her flock of alpacas and ran to her small home with her 8-year-old granddaughter, at hearing a roar that came from the sky, similar to thunder. She feared that the house was about to collapse as small stones rained down on the roof of her dwelling for several minutes after the object hit.

Initially the fall did not affect anyone, but there are rumors that a bull appeared dead. The local peasants feared that a disease outbreak would occur due to the scattered shards.

Indeed, between 100 to 200 people who came close to the meteorite crater soon reported feeling ill. The first police officers who came to investigate the scene also felt ill. In the following days the number of people falling sick rose. The patients were treated for nausea, headaches, diarrhea and vomiting. The locals made the decision to stop drinking from nearby water sources for fear of some contamination.

THE LEGEND OF STONES FALLING FROM THE SKY

Meteors, which are luminous phenomena that appear in the sky, are known since ancient times. For example, the Chinese text Ch'un-ch'iu (quoted by Peter M. Millman, American Scientist, Vol 59, 1971, p. 700-705) records that on 23 March 687 B.C.E. "stars fell like rain". The English playwright William Shakespeare, in his play Richard II, Act 2 (quoted by Millman, in the same article), makes the character Salisbury say: "I see your glory, like a shooting star, falling to the base of the earth from the sky". Nobody knew exactly what these luminous phenomena consisted in, but gradually some ideas began to emerge.

In 1803, Jean-Baptiste Biot, a young scientist of 29 years old, was sent by the Minister of the Interior to make a report on a spectacular rock fall occurred on 26 April, in the village of l'Aigle, 140 km northwest of Paris. At that time, the mere existence of these stones (nicknamed meteorites) was fiercely debated. Biot left Paris with a compass, a map of the area and a sample of a stone that was also said had fallen from heaven (over Barbotan, in 1790). He made clear that his spirit was to be "a witness stranger to any system" (Jean-Baptiste Biot, in "Mémoires de la classe de sciences mathématiques et physiques de l'Institut National de France 7", Paris, 1803, pages 224 through 265, quoted by Matthieu Gounelle, "The meteorite fall at L'Aigle on April 26th 1803 and the Biot Report", 66th Annual Meteoritical Society Meeting, 2003).

He did not begin his investigations in the village of l'Aigle, but several kilometers away, in the neighboring town of Alençon, in order to investigate the mineralogy of the region and learn about the local industry products and handicrafts. In his route between Alençon and l'Aigle, he questioned passengers and coach drivers about the luminous phenomenon seen in the sky on the same day that the stones fell. At l'Angle, he questioned the priest and his assistants, as well as common people, on the appearance of the stones and the luminous phenomenon.

Biot performed an analysis of the data available: there were a number of witnesses who claimed to have seen "a rain of stones that were thrown out of the [luminous phenomenon in the sky]" (Biot, in the work cited). These witnesses were from different professions, with varied interests and different socioeconomic levels. In the region there was no stone or artifact that was similar to the stones that were found. These stones, all identical, had appeared suddenly, and were similar to the stone found in Barbotan, that legend also said had fallen from the sky.

Biot concluded that the evidence pointed out that the stones were indeed of extraterrestrial origin.

INVESTIGATING THE EVENT IN PERU

A team led by José Macharé of the Mining and Metallurgical Geological Institute of Peru submitted a preliminary scientific report on what happened (Luisa Macedo & José Macharé, "The Carancas meteorite fall, 15 September 2007. Official INGEMMET initial report", Geological Mining and Metallurgical Institute of Peru, Lima, 21 September 2007).

The apparent flight of the meteor was toward the northeast. Its head was strongly luminous (white light) with a steaming white tail. No fall of any other object was observed after the fall of the main body. There was a loud explosion that was felt to the city of Desaguadero, 20 km from the impact site. Some windowpanes of the local Health Center were broken, distant 1 km from the site. The sound of the explosion continued rumbling for many minutes.

The impact created a crater in the soft ground. The maximum height of the circular-shaped edge wall is 1 m above the original ground level, right in the northern part of the crater. The crater ejecta consist of brown earth with a kind of grayish varnish (meteoric dust), and were found to 200 m from the impact point.

This crater is comprised of a hole and an edge in the shape of a raised wall, circular, formed by the ejected material. The central hole became a puddle, because it was filled with underground water which was filtered after impact. The size of the pond is from 7,4 to 7,9 m, while the entire crater with its ring-shaped edge is between 13,3 and 13,8 m.

After the impact boiling water was seen inside the crater, and was formed a column of smoke that lasted several minutes. A "sulfurous" smell was reported.

Three days after the fall, the water in the pool was at 1 m below the original ground level. It looked murky brown.

The chemical composition of the pond water and soil samples from the area of impact is being analyzed. No radioactive material was detected associated with the meteorite.

The point of impact is located on an elevated plain, of sedimentary rocks. The area is of a reddish brown earth, and this layer is a few meters thick.

At first glance the space material is rocky, brittle, fine-grained, light gray, and has dispersed in it iron particles of 1 mm in diameter.

When geologist Luisa Macedo arrived, 36 hours after the impact occurred, villagers had already taken over the larger fragments of the meteorite.

The fragments collected were taken to the laboratory, where cuts were made in the form of thin slices, which were then polished and prepared for petro-mineralogical determinations with an optical microscope. Tests performed by Teresa Velarde, Cesar Canepa, Hans Bernhardt and Laura Plascencia, with Vincentina Cruz on geochemistry, revealed that its texture corresponds to the category of chondrites, and is composed of the mineral pyroxene type-1 up to 40%, olivine 20%, 15% kamacita, 10% feldspar, type-2 pyroxene up to 10%, triolita (5%) and traces of chromite and native copper.

From the field observations and the information provided by the Director of Health of the Region of Puno, the initial report that about 200 people were affected by headaches, vomiting and stomach pains seems exaggerated. The number of people who felt ill would be about 30.

The causes are still unknown, but speculations range from the dust raised by the impact, through groundwater vapors that contain arsenic, to effects due to the psychological stress that these people suffered by an event so terrifying. The composition of the meteorite would have no relationship.

OTHER IMPORTANT METEORITE FALLS

At 10:38 in the morning of 12 February 1947, near the Sikhote-Alin Mountains in Russia, a huge ball of fire brighter than the Sun was seen, and minutes later were heard detonations that broke windows, opened doors and blew up plaster from walls. On the horizon a huge plume of white smoke appeared, with pink and blue blazes. The meteorite had shattered already in the air, and thousands of fragments fell into an elliptical area of about 1 km x 2 km, leaving more than a hundred craters, the largest of 26 m in diameter and 6 m deep. It is estimated that the total mass reached 70 ton. Chemical analysis indicated that it was predominantly pure iron, with 5,9% nickel, 0,4% cobalt, 0,5% phosphorus, about 0,3% sulfur and traces of other elements.

Another event, on 4 March 1960, in Bruderheim, Canada, left black stones scattered in an ellipse of 3 km x 5 km on the white snow. The largest was 30 cm and the smallest ones were like grains of wheat. About 700 pieces were recovered, totaling about 300 kg.

Another important event occurred in Allende, Mexico, in 1969; about two thousand kilograms were recovered from an extensive area.

Among the stony meteorites, the most massive event occurred on 8 March 1976, in Jilin, China. 4 tons of fragments were recovered, the largest of which produced a crater 6 meters deep.

On 9 October 1992 a fireball fell in Peekskill, USA; one of its fragments pierced the trunk of a parked Chevrolet Malibu.

At 9:22 h on 15 February 2013, a large bolide, brighter than the sun, was seen by the public and recorded by numerous video cameras over the region of Chelyabinsk, Russia. Minutes later, a powerful shockwave arrived on populated areas and caused widespread damages especially to window glasses. Numerous people sought medical care. In the aftermath, small pieces began to be retrieved from the snow and days later a hole was found on an ice layer of a lake of the general area. After months of search and efforts, a 540 kg mass of stony meteorite was raised to the surface. In total, about a ton of material was collected.

The only proven case of a human who was hit by a space rock occurred on 30 November 1954 , in Sylacauga, USA: a chondrite-type stone, of 4 kg, went through the roof of a house and hit Ann Hodges, who suffered ugly bruises on her hip. In total, at least 1062 proven falls are in the records. There are even some whose leftover find's current whereabouts is unknown, as one in Paraguay, dated 20 July 1925, that occurred in Villarrica. From the event a stony meteorite 12-cm long, 7-cm high and 5,5-cm wide would have been recovered. Maybe it was stolen by one of those embarrassing meteorite hunters, who do not respect the laws and scientific ethics. Maybe it was misclassified and rests on a shelf in the cellar of some museum. Or maybe it never was. A mystery that awaits researchers in the spirit of being "a witness stranger to any system" of preconceived thoughts.

Aldo Loup.

Originally published in ABC Color, on 5 November 2007. Picture: The crater left by the meteorite fallen in Carancas, Puno region, Peru, on 15 September 2007, photographed using a 6-m height pole. The amount of earth sent up in the air is proof of the violence of the explosion. The pond is groundwater seepage. Credit: Prof. Dr. Thomas Kenkmann / Natural History Museum - Leibniz Institute for Research on Evolution and Biodiversity at the Humboldt University of Berlin. Copyright © 2008 Thomas Kenkmann. With permission from Thomas Kenkmann, now at the Institute of Geosciences, University of Freiburg, Germany.