In testimony Thursday, Air Force Brig. Gen. Simon P. Worden told members of the House Science Subcommittee on Space and Aeronautics that the United States has instruments that determine within one minute if an atmospheric explosion is natural or manmade.
But none of the other nations with nuclear weapons have that detection technology, and Worden said there is concern that some of those countries could mistake a natural explosion for an attack and immediately launch an atomic retaliation.
Worden, deputy director for operations of the U.S. Strategic Command, said there was the risk of such a mistaken atomic exchange last August when Pakistan and India, both with atomic bombs, were at full alert and poised for war.
Not far away, a few weeks before, Worden said, U.S. satellites detected over the Mediterranean an atmospheric flash that indicated "an energy release comparable to the Hiroshima burst." Air Force instruments quickly determined it was caused by an asteroid 15 feet to 30 feet wide.
"Had you been situated on a vessel directly underneath, the intensely bright flash would have been followed by a shock wave that would have rattled the entire ship, and possibly caused minor damage," Worden said in his testimony.
Although the explosion received little or no notice, the general said it could have caused a major human conflict if it had occurred over India or Pakistan while those countries were on high alert.
"The resulting panic in the nuclear-armed and hair-triggered opposing forces could have been the spark that ignited a nuclear horror we have avoided for over a half-century," he said.
Worden said the Air Force's early warning satellites in 1996 detected an asteroid burst over Greenland that released energy equal to about 100,000 tons of explosives. He said similar events are thought to have occurred in 1908 over Siberia, in the 1940s over Central Asia and over the Amazon basin in the 1930s.
"Had any of these struck over a populated area, thousands and perhaps hundreds of thousands might have perished," he said.
Worden said early warning satellites do a good job of detecting asteroid bursts in the atmosphere and that new equipment will be even better. He said the Air Force is working on an asteroid alert program that would quickly send information from the satellites to interested nations.
He said the Air Force is studying the establishment of what he called a Natural Impact Warning Clearinghouse that would be part of the North American Aerospace Defense Command communications center in Cheyenne Mountain near Colorado Springs, Colo.
NASA is in the midst of a 10-year program to find and assess every asteroid six-tenths of a mile or more in size that could pass close to the Earth and might pose a danger to the planet.
Such asteroids or comets are called "near earth objects" and if one struck the planet it could wipe out whole countries. An asteroid 1 mile across could snuff out civilizations, while one that is 3 miles across could cause human extinction, experts say.
Edward Weiler, head of NASA's office of space science, told the House committee that his agency has detected 619 near earth objects and is finding about 100 new ones each year. None poses a danger to the Earth.
Worden and others said that smaller asteroids also can be destructive. For instance, if an asteroid the size of a cruise ship smashed into the ocean it could cause huge waves, called tsunamis, capable of drowning coastal cities on two continents.
Worden called for a system of instruments and telescopes on land and in space that could scan the sky to find asteroids down to the size of 300 feet. He said telescopes and instruments weighing less than 150 pounds could easily be launched to establish an observing network.
By Paul Recer