Meteorite suggests younger cosmic roots for Earth

U. CHICAGO (US)—The interstellar stuff that became incorporated into the planets—and life on Earth—has younger cosmic roots than theories predict, according to an international team of scientists.

University of Chicago postdoctoral scholar Philipp Heck and his colleagues examined 22 interstellar grains from the Murchison meteorite flung into space by dying sun-like stars 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 says.

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 and 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 says.

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.

Also contributing to the study were researchers from Washington University at St. Louis; Max Planck Institute for Chemistry in Mainz, Germany; the Institute of Isotope Geology and Mineral Resources in Zurich, Switzerland; and Australian National University in Canberra.

The study was supported by the National Aeronautics and Space Administration, Swiss National Science Foundation, the Australian National University, and the Brazilian National Council for Scientific and Technological Development.

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