Since then, there have been some spectacular near misses.On August 10,1972,an object around five meters(16 feet)across and weighing 150 tons traveled through the upper atmosphere.Hundreds of people saw its bright trail that sunny afternoon as it crossed the sky from Utah to Alberta before flying back out into space. On March 22,1989, a rock as big as 300 meters across came within several hundred thousand kilometers of Earth, which,in astronomical terms, is uncomfortably close.