An asteroid or comet about 10 kilometers in diameter struck the Yucatan peninsula 65 million years ago and caused global devastation, probably wiping out large numbers of plant and animal species including the dinosaurs, the report states.

Objects as large as that strike Earth only about once every 100 million years on average, the report notes. NASA has been highly successful at detecting and tracking objects 1 kilometer in diameter or larger, and continues to search for these large objects. The report notes that NASA has managed to accomplish some of the killer asteroids mandate with existing telescopes but with over 6,000 known objects and countless others the task is relentless.

Objects down to sizes of about 140 meters in diameter -- which NASA has been mandated to survey for -- would cause regional damage; such impacts happen on average every 30,000 years, the report says.

The report recommends that NASA monitor for smaller objects -- those down to 30 to 50 meters in diameter -- which the report says recent research suggests can be highly destructive.

The report states that detailed studies of ways to mitigate collisions are best viewed as a form of insurance. How much to spend on these insurance premiums is a decision that must be made by the nation’s policymakers.