Speaker
Description
The presence of long-lived radionuclides in meteorites is the result of their interaction with cosmic rays. Consequently, the concentrations of these cosmogenic nuclides (CNs) reflect the extraterrestrial matter's irradiation history. The reconstruction parameters of interest are:
1. pre-atmospheric size and shielding depth of the body in space (meteoroid)
2. irradiation time in space (irradiation age)
3. identification of complex exposure, i.e., repeated collisions or inherited CNs from pre-exposure at the surface of the meteoroid’s parent body (asteroid, Moon, Mars)
4. residence time on Earth (terrestrial age) for meteorite finds.
Accelerator Mass Spectrometry (AMS) is the method-of-choice for detecting long-lived CNs such as 10Be, 14C, 26Al, 36Cl and 41Ca with half-lives ranging from 6 ka to 1.4 Ma. However, tedious radiochemical separation [[1]] to deplete matrices and isobars was previously a prerequisite for AMS preventing fast and reasonable analysis.
Now, the world-wide unique Ion-Laser InterAction Mass Spectrometry (ILIAMS) system, developed at the Vienna Environmental Research Accelerator (VERA), provides isobar suppression by up to fourteen orders of magnitude [[2]]. Hence, ILIAMS-assisted AMS, enables the direct detection of 26Al/27Al (~10-10) and 41Ca/40Ca (~10-11) in crushed stony meteorites containing ~1% intrinsic Al and Ca. Because ILIAMS suppresses the naturally abundant isobars (~15% Mg, ~1‰ K) so effectively, tedious radiochemical separation is no longer necessary. This approach has been successfully applied to recent European meteorite falls like Drélow, Elmshorn [[3]], Haag [[4]], Kindberg, Koblenz, Ribbeck [[5]] and Saint-Pierre-le-Viger [[6]], as well as to meteorite finds. We can also quite easily decipher true meteorites from meteor-wrongs [[7]].
Most remarkably, a stacked-foil detector allowed the use of Be2+ (rather than Be3+), thereby, boosting 10Be measurement efficiency by an order of magnitude. We are proud to announce a promising new "hydrofluoric acid (HF)-free" method for 10Be analysis in stony meteorites, which aims to minimise hazardous chemistry for this widely accepted radionuclide.
For iron meteorites, chemistry is still needed, but ILIAMS allows easy isobar suppression and very efficient 36Cl, 41Ca and 26Al (by high current AlO-) determination. Other CNs such as 53Mn (t1/2=3.7 Ma) and 59Ni (t1/2=0.1 Ma) are currently under investigation. The latter will be an ideal nuclide to determine longer terrestrial ages exceeding the typical 50 ka limit of (often troublesome for iron meteorites) 14C dating. The validation of 59Ni dating by alternative methods such as 36Cl-41Ca-dating [[8]] is work-in-progress on a larger set of iron meteorites including Agoudal, Hoba, Kunova Teplica, Santa Catharina, Smolenice, and – yet unpublished - recent finds.
Acknowledgments: We thank A. Bischoff, D. Heinlein, L. Ferrière, A.J. Jull, M. Patzek, A. Patzer, P.P. Povinec, and J. Zipfel for very valuable meteorite samples, and the VERA team, especially S. Adler for assistance with AMS.
References: [1] Merchel & Herpers, Radiochim. Acta (1999). [2] Martschini et al., Radiocarbon (2022). [3] Bischoff et al., Meteorit. Planet. Sci. (2024). [4] Bischoff et al., Meteorit. Planet. Sci. (2025). [5] Bischoff et al., Meteorit. Planet. Sci. (2024). [6] Egal et al., Nat. Astron. (2025). [7] Pittarello et al., Meteorit. Planet. Sci. (2025). [8] Smith et al., Meteorit. Planet. Sci. (2019).