Those were just some of the conclusions included in a report, “Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies,” issued today from scientists at the National Research Council on what options NASA has to detect more near-Earth objects (NEOs) -- asteroids and comets that could pose a hazard to Earth.

The same council issued a preliminary report in saying imminent impacts (such as those with very short warning times of hours or weeks) require better current discovery capabilities. Existing surveys are not designed for this purpose; they are designed to discover more-distant NEOs and to provide years of advance notice for possible impacts. In the past, objects with short warning times have been discovered serendipitously as part of surveys having different objectives. Search strategies for discovering imminent impacts need to be considered, and current surveys may need to be changed.

No matter what though, the report says the $4 million the US currently spends annually to search for comets and asteroids is insufficient to meet a congressionally mandated requirement on NASA to detect NEOs that could threaten Earth.

The report states that while impacts by large comets or asteroids are rare, “a single impact could inflict extreme damage, raising the classic problem of how to confront a possibility that is both very rare and very important. Far more likely are those impacts that cause only moderate damage and few fatalities.”