|Central Mexico’s Lake Cuitzeo contains melted rock formations|
and nanodiamonds that suggest a comet impacted Earth around
12,900 years ago, scientists say.
This impact would have been powerful enough to melt the ground, and could have killed off many large mammals and humans. It may even have set off a period of unusual cold called the Younger Dryas that began at that time, researchers say.
The idea that Earth experienced an asteroid or comet impact at the start of the Younger Dryas has been controversial, in part because there is no smoking-gun impact crater left behind as with other known events in our planet's past. But researchers say it's common for space rocks to disintegrate in the heat of a planet's atmosphere before they can reach the ground.
The scientists first reported their suspicions about the event in 2007. Now, they say, a new site in Central Mexico's Lake Cuitzeo displays telltale signs of an impact, including melted rock formations called spherules and microscopic diamonds that could only have formed under extreme temperatures.