Broadcast (2009) Approximately 13,000 years after the mighty mammoth and 35 other groups of mammals vanished from North America, some scientists pose the controversial theory that a massive impact from space may have heralded their demise. For the past four decades, experts have been at odds over what causes this mass extinction. While mainstream scholars pose that the changing climate or ancient hunters were likely to blame for driving the beasts into oblivion, others believe that a comet from deep space may have broken up over North America.This would have caused a devastating series of explosions that decimated the landscape, and wiped out animal populations. The proof, they claim, lies in the discovery of a mysterious black mat layer at over fifty sites across the continent. The materials found in the "black mats" include rare, microscopic "nanodiamonds," which are thought to be the product of extraterrestrial impact. In this documentary, filmmakers pose that perhaps all three theories share an common element of truth.