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Determining inherited nucleosynthetic signatures in planetary bodies - Mo-Zr isotopic variations in the early solar system

English title Determining inherited nucleosynthetic signatures in planetary bodies - Mo-Zr isotopic variations in the early solar system
Applicant Wieler Rainer
Number 116753
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geochemie und Petrologie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.04.2008 - 31.03.2012
Approved amount 243'547.00
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All Disciplines (2)

Discipline
Geochemistry
Astronomy, Astrophysics and Space Sciences

Keywords (9)

Solar system formation; isotopes; meteorites; nucleosynthesis; core formation; chronology; isotopic anomalies; early solar system; solar nebula

Lay Summary (English)

Lead
Lay summary
Our solar system formed from the collapse of a molecular cloud containing various types of interstellar grains, produced by a variety of processes in stars and carrying distinct isotopic compositions. The solar system thus started as an initially heterogeneous mixture of isotopically distinct components. The evolution of the solar nebula therefore involved transport of mass, thereby reducing the initial isotopic heterogeneity. The major focus of this research is to determine the scale to which this initial heterogeneity in the nebula was erased by transport and mixing. Such constraints are critical for understanding the dynamics of the solar nebula and, hence, the early evolution of the solar system. The central question is whether gas and dust in the solar nebula were efficiently mixed and homogenized prior to the formation of the first planetary objects. If not, some level of isotopic heterogeneity is expected among the different planets. We use Mo and Zr isotopes to determine whether such planetary-scale heterogeneities exist. Mo isotopes are very useful to investigate nucleosynthetic variations in meteorites because several Mo isotopes are produced exclusively by one among different nucleosynthetic processes. Our data obtained with improved chemical and analytical methods unambiguously establishes planetary-scale Mo heterogeneities in the nebula and thus ends a decade lasting controversy. We identified a heterogeneous distribution of material produced in Red Giant stars as the cause for these heterogeneities. Further, the Mo isotopic anomalies seem to correlate with the accretion age of the planetary objects and their distance from the Sun. This implies that closer to the Sun the homogenization of the nebula was faster, an observation that is supported by numerical simulations. In addition, the Mo isotopic anomalies can be used to infer genetic relations between different planetary objects. Challenging the current paradigm, our measurements show that a chondritic uniform reservoir never existed and chondritic meteorites don't represent the (only) building blocks of the Earth. If there are Mo isotopic heterogeneities on a planetary scale, then there also should be collateral effects for other isotopes that have been produced by the same nucleosynthetic processes. Zirconium, one of the nearest neighbours of Mo, is an obvious element that could show such effects. As for Mo, reports of Zr isotope variations by some authors could not be confirmed by others. To better constrain the origin and nature of nucleosynthetic anomalies we'll acquire Zr data for bulk meteorites as well as components of primitive meteorites for which we already obtained Mo data.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Nucleosynthetic tungsten isotope anomalies in acid leachates of the Murchison chondrite: Implications for Hf-W chronometry
Burkhardt C., Kleine T., Wieler R. (2012), Nucleosynthetic tungsten isotope anomalies in acid leachates of the Murchison chondrite: Implications for Hf-W chronometry, in Astrophys. J. Lett., 753, L6-L6.
Molybdenum isotope anomalies in meteorites: Constraints on solar nebula evolution and the origin of the Earth. Earth and Planetary Science Letters
Burkhardt C, Kleine T., Wieler R (2011), Molybdenum isotope anomalies in meteorites: Constraints on solar nebula evolution and the origin of the Earth. Earth and Planetary Science Letters, in Earth planet. Sci. Lett., 312, 390-400.
Hf-W mineral isochron for Ca,Al-rich inclusions: Age of the solar system and the timing of core formation in planetesimals.
Burkhardt C., Kleine T (2008), Hf-W mineral isochron for Ca,Al-rich inclusions: Age of the solar system and the timing of core formation in planetesimals., in Geochim. Cosmochim. Acta, 72, 6177-6197.

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