The asteroids, named 1998 OH and 1998 OR2, were detected last month through NASA's Near-Earth Asteroid Tracking system, using a remote-controlled telescope operated by the Air Force at the 9,000-foot summit of Haleakela on the Hawaiian island of Maui.
NEAT, begun in 1995, scans the skies six nights each month when the Air Force isn't using the telescope to monitor satellites. The program recently installed new computing and data analysis hardware to speed up the search for rocky bodies that potentially could slam into the Earth or come dangerously close, said Steven Pravdo, the NEAT project manager at NASA's Jet Propulsion Laboratory in Pasadena.
1980 OH was discovered on July 19; 1998 OH2 on July 24.
David L. Rabinowitz, a JPL co-investigator, made followup observations of the two objects using a 24-inch telescope at JPL's Table Mountain Facility in Wrightwood, Calif. He said their orbits did not pose any immediate hazard to Earth. However, each of the asteroids is large enough to pose a global threat.
Although the asteroids' precise paths have not yet been determined, preliminary projections indicate 1998 OH could get no closer than 3 million miles from Earth about 20 times the distance from Earth to the moon.
So far, asteroid trackers have detected only about 125 "potentially hazardous" asteroids and comets that periodically pass near Earth's orbit. Scientists believe there are as many as 2,000.
Eleanor Helin, principal investigator of NEAT, said the program goal is to "discover and track all the potentially dangerous asteroids and comets long before they are likely to approach Earth."
Scientists believe an asteroid slammed into Mexico's Yucatan Peninsula 65 million years ago, which led to the demise of dinosaurs and other species. In 1908, an asteroid exploded over Siberia, flattening nearly 1,000 square miles of forest.
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