BIR MOGHREIN, Mauritania — You may have seen a meteorite before, even if you didn’t know it. Nearly 100,000 pounds of meteoritic matter enters Earth’s atmosphere every day, scientists estimate.

and palladium. Those elements are generally rare on Earth, but common in meteorites, though they appear to have spread widely during the collision because they are found right across the Earth.

"This has been a decade-long detective story, with each recorded meteorite fall providing a new clue." Ten years ago, astronomers from various institutions, including NASA and SETI (Search for ...