Speaker
Jenny Feige
(Technical University Berlin)
Description
Each year, roughly 30,000 tons of extraterrestrial solid material, liberated from larger parent bodies within our Solar System, is captured by the Earth [1]. A significant fraction of this material are submillimetre-sized spherical to teardrop-shaped particles, termed micrometeorites. They represent signatures of asteroidal collisions and cometary sublimation [2], hence, the determination of their origin gives valuable information on recent cosmic events and processes. Their cosmic ray exposure age can be derived by measuring
cosmic ray-induced spallation products such as the long-lived radionuclides 26Al and 10Be that accumulate within the particles during their journey through space (e.g. [3]).
The low concentrations of 26Al and 10Be within micrometeorites are close to the detection limits of current accelerator mass spectrometry (AMS), hence, any loss of material for their identification and classification as micrometeorites needs to be minimized. Surface composition analyses with EDX-measurements can lead to misidentifications, since these particles have melted during entry, and do not represent the total composition. For identifying micrometeorites with high confidence, it is necessary to analyze the interior of the particle [4], commonly through epoxy embedded cross-section EDX-analysis, which, however, leads to substantial material loss [5].
We present a new methodology on how to identify micrometeorites without a substantial material loss, nor impediments such as coating and epoxy embedding. Using a focused ion beam (FIB) on the non-coated particle, we are able to cut off a thin slice of the surface. Subsequently, with field emission electron probe microanalysis (FE-EPMA), its inner composition (and textures) can be determined quantitatively at lower detection limits down to a few tens of ppm with wavelength dispersive X-Ray spectrometers. Here, we show first results on 50-150 um diameter micrometeorites collected from Antarctic moraine sediments originating from the Larkman Nunataks aeolian traps [6].
References
[1] S.G. Love and D.E. Brownlee, Science 262 (1993) 550.
[2] G.M. Raisbeck et al., 49th Ann. Meet. Meteorit. Soc. 600 (1986) 136.
[3] K. Nishiizumi et al., Meteorit. Planet. Sci. 30 (1995) 728.
[4] J. Larsen and M.J. Genge, 79th Ann. Meet. Meteorit. Soc. 1921 (2016) 6341.
[5] M.D. Suttle and M.J. Genge, Earth. Planet. Sci. Lett. 476 (2017) 132.
[6] M.D. Suttle, et al., 78th Ann. Meet. Meteorit. Soc., 1856 (2015) 5063.
Primary author
Jenny Feige
(Technical University Berlin)
Co-authors
Dr
Alessandro Airo
(Technical University Berlin)
Mr
Christof Sager
(Technical University Berlin)
Dr
Dirk Berger
(Technical University Berlin)
Mr
Jörg Nissen
(Technical University Berlin)
Mr
Martin Suttle
(Imperial College London)
Dr
Matthew Genge
(Imperial College London)
