The Ultimate Hazard?
Congress has ordered NASA to detect and track 90 percent of near-Earth objects 140 meters in diameter or larger by 2020. They're "a very significant threat to life on Earth if they strike in or near urban areas," according to an interim report from a National Research Council committee checking on current efforts at home and abroad. The interim "Near-Earth Object Surveys and Hazard Mitigation Strategies" report, posted Aug. 12 on the National Academies Web site, says NASA lacks funding to complete the job, and neither Congress nor the new administration has sought to fund the activity with new appropriations.
Congress originally directed NASA in 1998 to discover 90 percent of the objects 1 kilometer in diameter or larger that could strike the Earth, but surveys detected most of these larger objects, and attention then turned to smaller ones, the report states. The directive to find those 140 meters in diameter or larger came in 2005. The report adds this: "Even the diameter of the asteroid that created the only known serious historically-recorded damage, the 1908 Tunguska explosion that leveled about 2000 [square] km of Siberian forest, has been recently revised downward -- according to a single study -- from 50-75 meters to about 30-40 meters, thus causing a reassessment of the apparent risk from airblast due to impacts by small asteroids."
Near-Earth objects, or NEOs, are certainly out there; more were discovered in 2008 than in any previous year. The Lowell Observatory in Flagstaff, Ariz., performed sky scans with its telescope for NASA from 1993 to February 2008 and found 288 NEOs, the report says. Three search programs currently operate, including one MIT project funded by NASA and the U.S. Air Force that has found 2,210 NEOs, according to the report, but it says the three current surveys cannot meet the 2005 goals set for NASA.
The final report will be completed later this year.
Posted by Jerry Laws on Aug 15, 2009