Scientists have made a big step towards understanding the chemical state of the early solar nebula by studying the variation of iron isotopes in samples from meteorites, Earth and Mars. Using new state-of-the-art techniques developed in the Isotope Geochemistry Laboratory at Oxford University's Department of Earth Sciences, they have discovered that the early solar nebula appear to have been very well mixed prior to the formation of asteroids and their components, chondrules.
Knowledge about the degree of chemical and isotopic homogeneity of the solar nebula is a starting point in understanding the chemical evolution of the early solar system.
This fundamental issue is, however, notoriously difficult to pin down, because even the most primitive materials in the solar system today have already undergone chemical evolution.
Scientists at Oxford have now launched a program to study the isotope variations of transition metals.
Beginning with iron, a major component of solid materials in the solar system which has four naturally occurring stable isotopes, they have discovered that, although iron has been formed in different stars with different proportions of isotopes, it has been very well-mixed prior to planetary evolution.
This discovery challenges previous arguments about early solar heterogeneity based on some ambiguous evidence.
Dr. Xiangkun Zhu, who led the research project, said, "This discovery is of great significance in understanding the solar system evolution. We are now expanding our study to isotopes of other metals, such as those of titanium and zinc.
"All together, they are expected to provide significant new insights into some important processes operating in the early solar nebula, such as evaporation, condensation and metal-silicate fractionation."
(Reference: The paper "Isotope homogeneity of iron in the early solar nebula" is published in Nature 19.07.01. The authors are X.K Zhu, Y Guo, R K O'Nions, E D Young, R D Ash.)
19-Jul-2001
