Complex sentence: A search of the impact zone that began on December 2008 turned up of rocks in 280 fragments, which were leftovers from the meteoroid of a rare type known as ureilites, which contained, among other minerals, nanodiamonds.
Split into simpler sentences: A search of the impact zone that began on December 2008 turned up of meteorites in 280 fragments, which are surviving pieces of the meteoroid. The meteorites are of a rare type known as ureilites, which contain, among other minerals, nanodiamonds.