The story of the Ischgl meteorite is finally solved
Almost 50 years of investigations of the EN241170 fireball and its possible connection with the fall of the Ischgl meteorite have finally been successful.
The story of the Ischgl meteorite is finally solved A recently published paper in the Meteoritics and Planetary Science (MAPS) confirmed that Ischgl meteorite found in 1976 about 2 km northwest of the Ischgl town in Austrian Alps was associated with the fireball EN241170 (Mount Riffler), which was observed in Germany on the night of November 23/24, 1970, by 10 camera stations of the European Network. The meteorite was locked in the finder’s hands until 2008, when it was classified at the University of Innsbruck as an LL6 chondrite with very low weathering, implying a relatively short time between the meteorite fall and its retrieval. The reconstruction of the trajectory of the fireball was carried out for many years. Only recent investigations using the state-of-the-art Monte Carlo techniques reconstructed the fireball’s trajectory, its heliocentric orbit, pre-atmospheric mass, cosmic-ray exposure age, and determined the strewn field of fragments in agreement with the recovery location of the Ischgl meteorite. Radionuclide analyses of the Ischgl meteorite (708.1 g) were carried out already in 2013 in the Low-Background Gamma Spectrometry Laboratory of the Department of Nuclear Physics and Biophysics, which confirmed the presence of cosmogenic and primordial / radiogenic radionuclides. They helped to determine a pre-atmospheric radius of the Ischgl meteorite to be 25 ± 5 cm, representing a mass of 220 ± 50 kg (using its average density of 3.31 g/cm3), in agreement with the astronomical observations, confirming that the Ischgl meteorite originated from the EN241170 fireball. The results of the analysis of cosmogenic 26Al measured in the Ischgl meteorite, and their comparison with the Monte Carlo model of Leya and Masarik (MAPS, 2009), showed that its cosmic-ray exposure age is 1.7 ± 0.8 My. A comparison of 26Al data with the 22Ne/21Ne isotope ratio suggested a multistage scenario in the Ischgl history, expecting that it was first exposed to cosmic rays as a part of an asteroid, which was then disrupted by a collision with another body, and only after a few million years after that collision a fragment of the asteroid reached the Earth as the observed Ischgl meteorite. Such a scenario would allow the 26Al activity to enter into a new equilibrium, consistent with the observed meteorite size.
Almost 50 years of investigations of the EN241170 fireball and its possible connection with the fall of the Ischgl meteorite have finally been successful. Very good spatial and temporal agreement between the EN241170 meteorite fall and the subsequent Ischgl meteorite find, also supported by the presence of fresh fusion crust, low weathering, and data on stable and radioactive isotopes, suggest that the Ischgl meteorite originated from the fireball event that occurred on November 24, 1970 with the impact point near Mount Riffler. The comprehensive work presented in the MAPS paper was carried out by the Ischgl meteorite consortium consisting of 17 laboratories from 9 countries. This result places the Ischgl meteorite as a number three in the list of meteorites with observed fall and a known orbit (after the Příbram (1959) and Lost City (1970) meteorites), although presently there are already 55 meteorites with known orbit in the heliosphere. The long scientific story of the Ischgl meteorite after publishing in the MAPS paper also attracted worldwide media such as New York Times, Der Standard, World Today News, El Espectador, and many others. The research output has an Altmetric Attention Score of 78, which is a high-level measure of the quality and quantity of online attention that it has received. It is in the top 5% of all research outputs ever tracked by Altmetric.
M. Gritsevich,..., P.P. Povinec, I. Sýkora et al. Meteoritics & Planetary Science 59, 1658–1691 (2024). Pavel Povinec