15 July 2004
Asteroids fast-tracked to Earth
Numerical models suggest that major collisions between main-belt asteroids lead to a temporary increase in the rate of meteorite impacts on Earth. The calculations predict that some of the fragments produced in the collision will be dragged into orbits resonant with that of Jupiter, for fast-track delivery to the inner Solar System. A large number of fragments would have arrived here within a few hundred thousand years; in contrast, most meteorites falling today have been many millions of years in transit. For the first time it has been possible to test the theory, making use of a unique site in southern Sweden where fossil meteorites have been preserved in 480-million-year-old sediments. High-sensitivity measurements of the noble gas content of these meteorites show that some were exposed to cosmic rays for a mere 100,000 years. In younger sediments, the transit times are correspondingly longer.
Fast delivery of meteorites to Earth after a
major asteroid collision
PHILIPP R. HECK, BIRGER SCHMITZ, HEINRICH BAUR, ALEX
N. HALLIDAY & RAINER WIELER
Nature 430, 323–325 (2004); doi:10.1038/nature02736
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