Part 4, Chapter 13 Summary and Analysis

Since the 1800s, it was recognized that there was something odd about the rocks near Manson, Iowa. In 1953, scientists incorrectly determined that ancient volcanic activity was the cause. In fact, the cause was a huge meteor from outer space, 1.5 miles wide, weighing 10 billion tons, which smacked the Earth at 200 times the speed of sound. It left a hole three miles deep and 20 miles wide. Gradually, over 2.5 million years of ice age, the crater filled in with dirt.

Giuseppi Pizaai of Sicily discovered the first meteor on January 1, 1800. About 1,000 more were identified in the next century. By the early 1900s, astronomers were more interested in other stars than in asteroids. As the 21st century dawned, asteroids attracted renewed interest. As of July 2001, about 26,000 had been identified, half of those in just two years from 1999 to 2001. This is still only a...