The arrowhead made of meteoritic iron from Mörigen. Collection Bern History Museum. Photo: Thomas Schüpbach
In an interdisciplinary study by the Natural History Museum Bern, led by geologist Prof. Dr. Beda Hofmann, researchers have proven that a Bronze Age arrowhead found in Mörigen on Lake Biel, Switzerland, was definitely made of meteoritic iron. Scientific evidence was provided by physicist Prof. Dr. Marc Schumann of the University of Freiburg, using gamma spectrometry. "The unusual aspect of this project is that we worked in a very interdisciplinary way and combined methods from such disparate sectors as archaeology, meteorite research and particle physics," says Schumann. The results have been published in the Journal of Archaeological Science.
Meteoritic iron is very rare
Evidence of such early use of meteoritic iron is extremely rare. The arrowhead comes from the holdings of the Bern History Museum, is 39 millimetres long and weighs 2.9 grammes, and originates from a Bronze Age pile-dwelling site in Mörigen by Lake Biel (900 to 800 BCE), where it was found during excavations in the 19th century. In order not to damage the irreplaceable historical artefact, non-destructive examination methods had to be used for the analysis.
The art of making iron from ore has been known in Central Europe since the beginning of the Iron Age around 800 BCE. Before that time, the metal was considered extremely rare and precious - it was only known from meteorites. Archaeological objects made of meteoritic iron are extremely rare, and therefore were probably not used as an everyday item. Only 55 such objects are known from the whole of Eurasia and Africa, and these come from 22 sites, with nineteen objects alone from the tomb of the Pharaoh Tutankhamun in Egypt. However, only a few of the artefacts have been examined with modern analytical methods.
New methods for examining meteorites
The methods used in this study for the analysis of the arrowhead in Bern include light microscopy, scanning electron microscopy, X-ray tomography, X-ray fluorescence, muon-induced X-ray emission (MIXE) and highly sensitive gamma spectrometry. "Using gamma spectrometry we can produce a radioactive fingerprint from any sample and even find relatively transient isotopes," says Schumann. "Some of these isotopes are only produced in outer space." These include aluminium-26, which Schumann and his team was able to detect in the arrowhead. "This gave us unequivocal evidence that the material was from a meteorite which had been exposed to cosmic radiation in space for a long time."
Astonishing discovery
The surprising fact about the meteoritic iron was however that it did not derive from the nearby Twannberg meteorite strewn-field in the Jura region of Bern, Switzerland. With about 8.3 percent nickel, the amount of this element in the arrowhead is almost twice as much as that in the Twannberg meteorite. A high level of germanium also shows that it is very probably a type IAB meteorite. In addition, the rather low concentration of aluminium-26 indicates that the sample originates from the interior of a meteorite which originally had a mass of at least 2 tons.
There are only a few known large IAB iron meteorites in Europe. The most likely origin is assumed to be the meteorite "Kaalijarv", which fell in Estonia during the Bronze Age (approx. 1500 BCE). The fall of this meteorite produced several craters of up to 100 metres in diameter. Since the largest meteorite fragments exploded on the ground, many small splinters must have been produced. Further analyses in archaeological collections in Europe could provide clues to whether the trail of the arrowhead stretching from Mörigen to Estonia can be confirmed.
Summary:
- Original publication: Hofmann, B.A., Bolliger Schreyer, S., Biswas, S., Gerchow, L., Wiebe, D., Schumann, D., Lindemann, S., Ramírez García, D., Lanari, P., Gfeller, F., Vigo, C., Das, D., Hotz, F., v. Schoeler K., Ninomiya, K., Niikura, M., Ritjoho, N., Amato, A.: An arrowhead made of meteoritic iron from the late Bronze Age settlement of Mörigen, Switzerland and its possible source. In: Journal of Archaeological Science (2023).
DOI: https://doi.org/10.1016/j.jas.2023.105827
- The project was coordinated by the Natural History Museum Bern. Also involved were the Bern History Museum, the University of Freiburg's Institute of Physics, the Institute of Geological Sciences at the University of Bern, Switzerland, and the Paul Scherrer Institute in Villigen, Switzerland.
- Marc Schumann is Professor of Astroparticle Physics at the University of Freiburg's Institute of Physics. His research focuses on the experimental hunt for extremely rare processes, such as dark matter. He also constructs highly sensitive detectors which emit minimal radioactivity of their own.
