Meteor strike in Russia 'a rare event'
15 February 2013 Last updated at 13:32 GMT
A meteor crashing in Russia's Ural mountains has injured at least 500 people, as the shockwave blew out windows and rocked buildings.
Most of those hurt suffered minor cuts and bruises but some received head injuries, Russian officials report.
Elizabeth Pearson, an astronomer at Cardiff University, says that debris coming off a big asteroid is not a surprising event.