Antarctica has been a target in a cosmic shooting gallery over the past few million years. At least three big asteroids have exploded above the continent. And two of them were close enough to the ground to cause major damage. In fact, such an explosion over a populated region today could kill millions.

Scientists have found evidence of the explosions in the Antarctic ice.

Thirty years ago, for example, teams looking for meteorites atop the ice found a dark streak in the ice. The streak contained a lot of dust. The minerals in the dust grains were like those found in the most common type of meteorite. But they’d been changed by interactions with the ice. Scientists concluded the grains were embedded in the ice when an asteroid exploded above Antarctica about two and a half million years ago. A powerful shockwave slammed into the surface, showering it with dust grains.

Similar groups of dust grains have revealed two other explosions, both within the past half-million years. One of the asteroids weighed about a hundred thousand tons when it plunged into the atmosphere. It exploded so high that the damage was minimal. The other weighed a million tons. It exploded deep in the atmosphere. Heat from the blast vaporized a lot of ice, while a shockwave would have gouged a crater in the ice. Bits of the asteroid slammed into the surface – of the Antarctic shooting gallery.

More about asteroid impacts tomorrow.

Script by Damond Benningfield