Cosmic impact wiped out woolly mammoths?

Woolly mammoths - the gigantic cousins of modern day elephants - may have died as a result of climate change following a major cosmic impact near the end of the Ice Age.
A catastrophic event in Earth's history around 12,800 years ago scorched the air, melted bedrock and altered the course of Earth's history, researchers said.
However, exactly what the event was is unclear. Researchers say something - global-scale combustion caused by a comet scraping our planet's atmosphere or a meteorite may have slammed into the Earth's surface.
This event jump-started what Kenneth Tankersley, assistant professor of anthropology and geology at the University of Cincinnati, calls the last gasp of the last ice age.

"The climate changed rapidly and profoundly. And coinciding with this very rapid global climate change was mass extinctions," Tankersley said.
In Sheriden Cave in Wyandot County, Ohio, 100 feet below the surface, Tankersley has been studying geological layers that date to the Younger Dryas time period, about 13,000 years ago.

About 12,000 years before the Younger Dryas, the Earth was at the Last Glacial Maximum - the peak of the Ice Age.
Millennia passed, and the climate began to warm. Then something happened that caused temperatures to suddenly reverse course, bringing about a century's worth of near-glacial climate that marked the start of the geologically brief Younger Dryas, Tankersley explains.

Tankersley found ample evidence to support the theory that something came close enough to Earth to melt rock and produce other interesting geological phenomena.
Foremost among the findings were carbon spherules. These tiny bits of carbon are formed when substances are burned at very high temperatures.
The spherules exhibit characteristics that indicate their origin, whether that's from burning coal, lightning strikes, forest fires or something more extreme.
Tankersley says the ones in his study could only have been formed from the combustion of rock.
The spherules also were found at 17 other sites across four continents - an estimated 10 million metric tons' worth - further supporting the idea that whatever changed Earth did so on a massive scale.

It's unlikely that a wildfire or thunderstorm would leave a geological calling card that immense - covering about 50 million square kilometres.
"We know something came close enough to Earth and it was hot enough that it melted rock - that's what these carbon spherules are. In order to create this type of evidence that we see around the world, it was big," Tankersley said.
The study was published in the Proceedings of the National Academy of Sciences.