Scientists said the asteroid was on a path that took it just inside the moon's orbit, and they ruled out any chance of impact with Earth. They tracked the quarter-mile-wide asteroid's every move from NASA's Deep Space Network in California's Mojave Desert, especially since last week as it approached from the direction of the sun at 29,000 mph.
Its closest approach to Earth was pegged at a distance of 202,000 miles at 3:28 p.m. PST. In cosmic measurements, that's pretty close.
NASA said if the asteroid did smash into Earth, it would have created a crater roughly four miles across and 1,700 miles deep.
"If this were to hit Earth, it is large enough to knock out a major city," said Dr. Ed Krupp, director of the Griffith Observatory.
The last time a cosmic interloper this size came this close to Earth was in 1976, and it won't happen again until 2028.
Though astronomers are tracking space rocks more thoroughly, Krupp said, "Eventually we're going to get hit by something."
The Associated Press contributed to this report.