More and more fragments of the Twannberg meteorite are being found in the Bernese Jura. Over 2,200 pieces are now known, and the remains of this rare iron meteorite are highly prized by researchers for several reasons.
In the canton of Bern, above Lake Biel, on the Twannberg and Mont Sujet, lies one of Europe's most important meteorite strewn fields. Fragments of an extraordinary celestial body have been repeatedly discovered there for decades.
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The number of known finds has now risen to more than 2,200. This means the scale of the meteorite fall is significantly greater than initially assumed.
The Twannberg meteorite did not hit Earth as a single large block, but exploded on entering the atmosphere. Its debris was scattered over an area of around six kilometres in what is now the Bernese Jura.
Scientists estimate that the celestial body struck Earth around 175,000 years ago. Originally, it is thought to have measured between four and 20 metres and weighed at least 250 tonnes.
First discovery in 1984
The story of the meteorite discovery began on 9 May 1984. At the time, a Swiss farmer found an unusual block weighing around 15 kilograms in a field. At first it was unclear what it was. Subsequent analyses showed that the find consisted of iron and did indeed come from outer space.
In the decades that followed, further fragments were found. Above all, systematic searches with metal detectors led to a sharp increase in the number of known pieces.
"Ten years ago we had 400 fragments, now there are more than 2,200," explained geologist Beda Hofmann from the Natural History Museum in Bern to Swiss public broadcaster SRF.
Extremely rare meteorite
The Twannberg meteorite belongs to the group of iron meteorites and has been classified as part of the extremely rare IIG group. It is so far the only known IIG iron meteorite in Europe. Meteorites of this type are characterised, among other things, by an unusually low nickel content and a high proportion of phosphorus. Only a handful of specimens of this class are known worldwide.
For scientists the fragments are particularly valuable: they can provide clues to the composition and evolution of celestial bodies and offer a glimpse into the early history of our solar system.
Glaciers helped spread the debris
The finds are also of interest for research into the history of the Swiss landscape.
According to experts, some of the newly discovered fragments were transported by glaciers. Around 175,000 years ago, massive glaciers covered large parts of the Swiss Plateau – in places the ice sheet was more than a kilometre thick. Because the new finds have been discovered at higher altitudes than previous fragments, they can offer fresh insights into the vast masses of ice during the penultimate Ice Age.
This makes the finds, in a sense, double witnesses of time: they originally came from outer space but later became part of Earth's history and were shaped by the glacial landscape processes.
The search continues
The search on the Twannberg and Mont Sujet is far from over; researchers and meteorite hunters continue to use metal detectors to look for new remains.
However, this is more difficult than it sounds, because the soil also contains pieces of metal that have nothing to do with the meteorite, such as aluminium foil or nails. And anyone wishing to carry out a search needs a permit from the competent archaeological service.
The discoveries show the potential that the Swiss meteorite field still holds: with each additional fragment, researchers learn more about the original celestial body and the story of its impact.
