Meteorite grains divulge Earth's cosmic roots
June 15, 2009
This is University of Chicago postdoctoral scientist Philipp Heck with a sample of the Allende meteorite. The dark portions of the meteorite contain dust grains that formed before the birth of the solar system. The Allenda meteorite is of the same type as the Murchison meteorite, the subject of Heck’s Astrophysical Journal study. Credit: Dan Dry
The interstellar stuff that became incorporated into the planets and life on Earth has younger cosmic roots than theories predict, according to the University of Chicago postdoctoral scholar Philipp Heck and his international team of colleagues.
Heck and his colleagues examined 22 interstellar grains from the Murchison meteorite for their analysis. Dying sun-like stars flung the Murchison grains into space more than 4.5 billion years ago, before the birth of the solar system. Scientists know the grains formed outside the solar system
because of their exotic composition.
"The concentration of neon, produced during cosmic-ray irradiation, allows us to determine the time a grain has spent in interstellar space," Heck said. His team determined that 17 of the grains spent somewhere between three million and 200 million years in interstellar space, far less than the theoretical estimates of approximately 500 million years. Only three grains met interstellar duration expectations (two grains yielded no reliable age).
"The knowledge of this lifetime is essential for an improved understanding of interstellar processes, and to better contain the timing of formation processes of the solar system," Heck said. A period of intense star formation that preceded the sun's birth may have produced large quantities of dust, thus accounting for the timing discrepancy, according to the research team.
16 hours ago
Science magazine published this chronology of the discovery of our cosmic roots at the University of Chicago in period, 1975-1983:
In 1975 scientists at the University of Chicago uncovered evidence that the Allende meteorite incorporated poorly mixed supernova debris at the birth of the solar system.
R.S. Lewis et al. (1975): "Host phase of a strange xenon component in Allende", Science 190, 1251-1262.
Until 1983, UC scientists mistakenly attributed the finding to fission products from a superheavy element.
O.K. Manuel and D.D. Sabu (1977): "Strange xenon, extinct superheavy elements and the solar neutrino puzzle", Science 195, 208-209.
B. Srinivasan and E. Anders (1978): "Noble gases in the Murchison meteorite: Possible relics of s-process nucleosynthesis", Science 201, 51-56.
R.S. Lewis (1983): "Barium isotopes in the Allende meteorite: Evidence against an extinct superheavy element", Science 222, 1013-1015.
With kind regards,
Oliver K. Manuel
http://www.omatumr.com/