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Asteroids have force of nuclear bomb
Compiled from Times wires WASHINGTON -- Asteroids regularly explode over the Earth with the intensity of a nuclear bomb; the explosions could be mistaken for a nuclear attack and even trigger an atomic war, an Air Force general said Thursday. Experts from NASA, the Air Force and the National Academy of Sciences told the House Subcommittee on Space and Aeronautics that larger asteroids pose an even more grave threat that, while it is extremely remote, needs to be taken seriously. "We are the first generation of humanity to recognize this danger, and the first with the technology to detect it," said David Morrison, an asteroid specialist at NASA's Ames Research Center in Mountain View, Calif. The chairman of the subcommittee, Rep. Dana Rohrabacher, R-Calif., said, "Objects out in space could be heading toward Earth that would make Saddam Hussein look like a minor factor in our lives," At least 30 times a year, a space rock measuring a few yards across slashes into the atmosphere and explodes, releasing energy equal to that of an atomic bomb, Air Force Brig. Gen. Simon Worden told subcommittee members. Worden, deputy director for operations of the U.S. Strategic Command, said the United States has satellite instruments that determine within a minute if the explosion is a nuclear weapon or a natural explosion from an asteroid. But no one else has such technology, he said, and without it, some countries conclude the explosions came from a nuclear bomb and could launch an atomic attack against an enemy. For instance, Worden said Pakistan and India, both of which have the atomic bomb, were at full alert in August, 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 testified. The explosion received little or no notice, the general said, but it could have caused a major human conflict had it 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 that the current generation of 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 of every asteroid 1 kilometer (0.6 miles) 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. If an asteroid 1 kilometer in size 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. Scientists believe large asteroids hit Earth on average about every 100-million years -- the last time being a 10-mile-wide asteroid that struck off the Yucatan Peninsula 65-million years ago. It helped drive the dinosaurs to extinction. "We can already state with assurance that there are no asteroids this large with orbits that could pose a threat to us," NASA's Morrison said. "But there is still a risk from objects down to 1 mile in diameter that could perturb the climate on a global scale and possibly collapse civilization." One kilometer asteroids are relatively rare, but 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. The Minor Planet Center at the Smithsonian Astrophysical Observatory in Cambridge, Mass., has records of about 1,800 near-Earth objects as small as 600 feet or so across. An asteroid roughly that size passed within 75,000 miles from Earth just last summer, but wasn't detected until it was already moving away. "Something that size could wipe out Southern California. I don't take a lot of comfort that an object like that missed us by an astronomical hair, and we didn't see it coming," Rohrabacher said. 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. Spending money to find possibly dangerous asteroids is "like fire insurance on your home," Morrison said. "You don't expect a fire, but you buy insurance even for an unlikely event." Currently, the U.S. government is spending less than $4-million a year to detect dangerous asteroids and figure out what to do about them. The subcommittee's witnesses urged a substantial increase. Rohrabacher worries that NASA's search effort isn't enough and wants to encourage amateur astronomers to get more involved. The House this week approved his plan for a set of three $2,000 awards, named after the late Apollo 12 commander Charles "Pete" Conrad, that would recognize amateur stargazers who "discover new and track previously identified large asteroids, particularly those that threaten close approach to the Earth." Sen. Bill Nelson, D-Fla., a space advocate and one-time space shuttle passenger while in the House, has told Rohrabacher that he will introduce a companion bill in the Senate. Brian Marsden, director of the Minor Planet Center, said amateur astronomers "occasionally" are the first to report a new near-Earth object, "but where they really contribute is with the necessary follow-on observations that must be done and reported to the database to establish the path the object is taking," he said. "Certainly encouraging them in these contributions is worthwhile." But even with dedicated backyard astronomers, experts worry that there's no national plan for tracking down the other mid-sized asteroids, let alone even smaller chunks that could still be dangerous. "There's no coordinated national policy, no one agency responsible for addressing this issue," Rohrabacher said, nor any planning for how to divert or otherwise protect Earth from impact if an asteroid on a collision course is found. A committee of the National Academy of Sciences, the nation's premier scientific organization, issued a report in July recommending a $125-million project to build a new, ground-based telescope that would take a picture of the entire sky every week, picking out moving objects as small as 1,000 feet across. Weiler said NASA was working on a nuclear space-propulsion system that could intercept an incoming asteroid swiftly and perhaps nudge it safely off course. "If we find something coming at us and we don't have a lot of time, we'll want to get there fast," he said. -- Information from the Associated Press, Knight Ridder Newspapers and Scripps Howard News Service was used in this report.
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