Comet or meteorite? A hundred-year-old mystery solved

Ars Technica : Earlier this year a meteor struck in the region of Chelyabinsk, Russia ; automobile dashboard cameras recorded the event and CCTV networks provided fixed reference points. But no such technology existed more than a century ago when a much larger object came streaking to Earth and landed near the Tunguska River in a Siberian forest. In fact, it is only recently that scientists have been able to definitively determine what caused the hundreds of square kilometers of devastation. Early on 30 June 1908, a gigantic fireball reportedly streaked across the sky, scorched everything in its wake, and struck the ground with such force that it knocked people off their feet. Despite leveling a large forest, the object from outer space appeared to leave no trace and so was assumed to have been a comet. Now, 105 years later, a group of scientists from the US, Ukraine, and Germany have sifted through the Siberian peat and discovered the microscopic remains. Using scanning and transmission electron microscopy, the researchers have found tiny inclusions of iron sulphides, iron–nickel alloys, troilite, and taenite—minerals that indicate the object was most probably a meteorite.