Previously, scientists thought that any asteroid or comet collision would leave strong evidence of the element iridium, the signal found in the sedimentary layer from the time of the dinosaur extinction. Iridium was found at the Permian-Triassic boundary, but not nearly in the concentration as from the dinosaur extinction. Becker believes that difference is because the two space bodies that slammed into Earth had different compositions. Funding for the research was provided by NASA's Astrobiology and Cosmochemistry programs and the National Science Foundation. Today a half-km asteroid is passing by the Earth 12 times farther from our planet than the Moon.
Scientists say it's an unusually good opportunity to study a near-Earth object.
NASA scientists are monitoring a large near-Earth asteroid that tumbled past our planet on Halloween 2000.