Mass Extinction????

Space rocks are still the probable cause of many mass extinctions that have occurred in our history. The threat of another space rock impaction Earth is a very real threat, felt by most Americans. That led Congress to task NASA with finding 90% of nearby space rocks greater than 140 meters. According the the Nation Research Council, this program is in risk of not meeting its goal, due to funding shortages. Nasa has detected and tracked almost 90% of near-Earth objects greater than 1 km. This being said, objects much small could still cause much damage to Earth's population. Even with all of our technology, some near-Earth objects are still detected entirely by chance, by people with telescopes or researchers carrying out other tasks. Some near-Earth objects are detected during space shuttle flights. The National Research Council's final report won't be complete until the end of 2009. Lets hope that NASA doesn't run out of funding for this very important program because if giant asteroid collides with Earth, we could be looking at a mass extinction.

source:http://www.popsci.com/military-aviation-amp-space/article/2009-08/no-free-lunch-detecting-dangerous-space-rocks