Refractory Metal Inclusions
Condensation Processes in the Early Solar System
T. Berg1,2, E. Marosits2, J. Maul1, G. Schönhense1, U. Ott2 and H. Palme3
1Institut für Physik, Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany
The earliest solid constituents of the solar system, that are widely believed to have formed by condensation, are so-called Calcium-Aluminum-rich Inclusions (CAIs). The ages of CAIs were determined by lead-isotope measurements. The result for CAIs from the meteorite Efremovka (4567±1 · 106 years) represents the nowadays accepted age of the solar system .
Fig. 1: A fragment of the meteorite Allende that fell in 1969 over Mexico. It is interspersed with light inclusions, so-called CAIs.
We investigated the size distribution (by scanning electron microscopy, SEM) and chemical composition (by energy dispersive X-ray spectroscopy, EDX) of so-called Refractory Metal Nuggets (RMN)  with sizes between ~100nm and ~1μm, that almost exclusively occur inside CAIs. Our measurements suggest a gas-to-solid condensation origin of these particles and provide direct evidence for condensation processes in the early solar system.
Fig. 2: SEM image of a refractory metal nugget identified in an acid resistant SiC-rich Murchison residue that was prepared for the analysis of presolar dust.
First results were published in:
Evidence for Structurally Controlled Condensation of Sub-micron Refractory Metal Alloys in the Murchison Meteorite
 "Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions“, Y. Amelin et al., Science 297(2002)1678-1683.
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