... Supernova showered Earth with radioactive debris . ... space flight . ... space physics . ... NASA space telescope finds fewer mid-size range asteroids near Earth . ... New observations by NASA's Wide-field Infrared Survey Explorer (WISE), show there are significantly fewer near-Earth asteroids in the mid-size range than previously thought. The findings also indicate NASA has found more than 90 percent of the largest near-Earth asteroids, meeting a goal agreed to with Congress in 1998. ...