A huge asteroid will fly past Earth within the moon's orbit on Tuesday, the closest such a large object has passed by our planet since 1976.
Asteroid 2005 YU55 will come within 324-thousand kilometers of Earth at 23:28 Universal Time, or UTC, Tuesday. The close encounter will give scientists a rare chance to study a near-Earth object without launching a space probe. The U.S. space agency says there is no chance that the spherical asteroid will collide with Earth or the moon.
NASA scientists plan to bounce radio waves off the asteroid and analyze the radar echoes. Those images should reveal details about the rock's surface features.
YU55 is about 400 meters in diameter and should be visible from the northern hemisphere with telescopes. Its path will be too dim to be seen with the naked eye.
The asteroid's close encounter is not expected to have any detectable effect on earth.
Scientists believe 2005 YU55 has been passing by Earth for thousands of years. It is one of about 8,500 near-Earth objects that NASA has catalogued.
Some information for this report was provided by AP, AFP and Reuters.