New studies are bringing to light the scars of many huge meteorites on the face of the earth. Most meteorites, no bigger than grains of sand, burn to ashes before reaching the ground. But a few larger ones reach the ground and rest there as pebbles or even boulders. Once in thousands of years and maybe more often in the dim past, a giant meteorite perhaps a mile or more wide strikes the earth with a furious impact.

The new word astrobleme, meaning the star wound, has been coined to name these dramatic events. Though such a whack from the sky was more common when the earth was young, it can still happen. Once in this century a remote region in Siberia was struck by what some think was the head of a stray comet. A few years later, this remote wilderness was struck again. What may have been a giant meteor exploded in the air and the ground below was punctured with hundreds of small craters.