CAPE CANAVERAL, Fla. (AP) -- A 45-meter (150-foot) asteroid hurtled toward Earth's backyard, destined Friday to make the closest known flyby for a rock of its size.
NASA, the U.S. National Aeronautics and Space Administration, promised the asteroid would miss Earth by 17,150 miles (27,600 kms), avoiding catastrophe. But that's still closer than many communication and weather satellites; scientists insisted these, too, would be spared. The closest approach is expected around 2:25 p.m. EST.
Asteroid 2012 DA14, as it's called, is too small to see with the naked eye even at its closest approach around 1925 GMT, over the Indian Ocean near Sumatra.
The best viewing locations, with binoculars and telescopes, are in Asia, Australia and eastern Europe. Even there, all anyone can see is a pinpoint of light as the asteroid zooms by at 17,400 mph (28,000 kph).
As asteroids go, DA14 is a shrimp. The one that wiped out the dinosaurs 65 million years ago was 6 miles across. But this rock could still do immense damage if it struck, releasing the energy equivalent of 2.4 million tons of TNT and wiping out 750 square miles (1,950 square kms).
Scientists are certain it won't impact Earth. And chances are extremely remote it will run into any of the satellites orbiting 22,300 miles (36,000 kms) up.
Most of the solar system's asteroids are situated in a belt between the orbits of Mars and Jupiter, and remain stable there for billions of years. Some occasionally pop out, though, into Earth's neighborhood.
The flyby provides a rare learning opportunity for scientists eager to keep future asteroids at bay -- and a prime-time advertisement for those anxious to step up preventive measures.
"We are in a shooting gallery and this is graphic evidence of it," said former Apollo astronaut Rusty Schweickart, chairman emeritus of the B612 Foundation, committed to protecting Earth from dangerous asteroids.
Schweickart noted that 500,000 to 1 million sizable near-Earth objects -- asteroids or comets -- are out there. Yet less than 1 percent -- fewer than 10,000 -- have been inventoried.
Humanity has to do better, he said. The foundation is working to build and launch an infrared space telescope to find and track threatening asteroids.
DA14 -- discovered by Spanish astronomers last February -- is "such a close call" that it is a "celestial torpedo across the bow of spaceship Earth," Schweickart said in a phone interview Thursday.
Astronomers organized asteroid-encounter parties for Friday and experts just about everywhere were giving flyby rundowns.
NASA's deep-space antenna in California's Mojave Desert was ready to collect radar images, but not until eight hours after the closest approach given the United States' poor positioning for the big event.
Scientists at NASA's Near-Earth Object program at California's Jet Propulsion Laboratory estimate that an object of this size makes a close approach like this every 40 years. The likelihood of a strike is every 1,200 years.
If a killer asteroid was, indeed, incoming, a spacecraft could be launched to nudge the asteroid out of Earth's way, changing its speed and the point of intersection. A second spacecraft would make a slight alteration in the path of the asteroid and ensure it never intersects with the planet again, Schweickart said.