陨石深埋宇宙奥秘，揭示地球生命起源。班主任金洁第二部系列

　　On a bright, cold morning on 15th February 2013, a meteorite ripped across the skies above the Ural mountains in Russia, distintegrating into three pieces and exploding with the force of 20 Hiroshimas. It was a stark reminder that the Earth's journey through space is fraught with danger. A day later another much larger 14,3000 tonne asteroid, passed within just 17,000 miles of ... (展开全部)