Astronomers have a good handle on the number of potential devastating near Earth objects (NEOs), asteroids and other objects more than one kilometer in diameter with orbits that swing by our planet. The impact threat from those objects is rare, occurring once every 100,000 years or so.
But more support is needed to track smaller objects, on the order of 100 meters wide, which are more common and could strike the planet every 1,000 years, scientists said during a hearing on NEOs before the Senate's Subcommittee on Science, Technology and Space.
"The impact of a 100-meter asteroid on Earth would cause significant damage," said Lindley Johnson, program manager of NASA's Near Earth Objects Observation Program to track the large objects. "And our systems are just not designed to find the small ones."
One such small object, Asteroid 2004 FH, buzzed past Earth on March 18, flying just 26,500 miles (42,647 kilometers) above the Pacific Ocean as it passed by. It was about 100 feet (30 meters) in diameter.
"It's the equivalent of riding an airliner and seeing a small plane pass by a few hundred feet outside the window," said Senator Sam Brownback (R-Kansas), who presided over the hearing. If such an object collided with Earth, it could release more than a megaton of energy and have the explosive yield of a nuclear weapon, he added.
Brownback said the subcommittee's main goal was to determine whether Congress should pass additional legislation to track more asteroids and other objects. Johnson's program, now in its fifth year, was launched at the behest of Congress and spends about $4 million each year seeking out large nearby objects.
Smaller NEOs
Johnson told Senate subcommittee members that his program has catalogued about 512 of the 700 known large NEOs known to exist. His team estimates about 1,100 total objects with one-kilometer diameters, and expects to track 90 percent of them by 2008.
Meanwhile, the number of small objects could be 100 times the amount of their larger near Earth counterparts.
"I think we could do a lot more," said Wayne Van Citters, director of the division of astronomical sciences for the National Science Foundation.
Citters said future scientific programs like the Large Synoptic Survey Telescope (LSST) and the University of Hawaii's Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) projects could make a large dent in the search for small NEOs. LSST is set for completion in 2011, while Pan-STARRS is scheduled to begin observations in 2006.
"The surveys would be complete somewhere between seven and 20 years from now," Citters said. "We could have information on objects down to 140 meters in diameter about 90 percent complete."
Additional arrays of ground telescopes or a moderately-priced space-based observatory, set somewhere in the orbit of Venus, would be a considerable asset not only to the search for near Earth asteroids, but to astronomers' understanding of the local universe.
"These objects are left over from the formation of the solar system, so as we catalog more of them we have a good probe of the early days of the solar system," Citters said.
Fitting into the space vision
Preparing deflection systems for NEOs could mesh well with NASA's new space vision to push forward with human exploration of space.
NASA astronaut Ed Lu told senators that an asteroid deflection mission could be ready for flight by 2015 and allow NASA the opportunity to test out new propulsion technologies or even send a human crew in preparation for long-duration crewed missions to Mars.
"I would personally love to go on one of those missions," Lu said of a crewed asteroid rendezvous effort. Lu is also president of the B612 Foundation, an organization of astronauts, scientists and engineers pushing for the 2015 deflection mission.
"This would not really be a planetary protection system, but it's a first chance to learn about asteroid deflection," Lu said. "The first time that you attempt to deflect and asteroid shouldn't be the real day you have to."
advertisement
