Key points from article :
Five chief goals to defend Earth from asteroid impacts.
National Near-Earth Object Preparedness Strategy and Action Plan.
Kinetic impactors would be flown into an NEO to disrupt its orbit.
Gravity tractors would fly close-by to slowly change its course.
NASA will also investigate the potential to use nuclear devices.
Over 300,000 objects larger than 40 meters could pose a hazard.
Need more detailed information from reconnaissance missions.
