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19 March 2004

Asteroid 2004 FH passes within three Earth diameters of Earth's surface

Steven R. Chesley and Paul W. Chodas of NASA's Near Earth Object Program Office issued a highly significant media release late Wednesday, March 17, 2004, while this issue of the E-Bulletin was being finalized. The release predicted the closest yet recorded passage by Earth of a near-Earth asteroid.

Asteroid 2004 FH was discovered on 15 March 2004 by the NASA-funded LINEAR asteroid survey. The asteroid, which is believed to be around 30 meters (around 100 feet) in diameter, was predicted to pass about 43,000 km (26,500 miles) above the Earth's surface on March 18, 2004. This is only slightly more than three times the diameter of Earth.

According to the media release, Earth's gravity was predicted to bend the asteroid's trajectory by about 15 degrees. The asteroid crosses from one side of the Moon's orbit to the other in 31 hours.

The close passage of 2004 FH is not unusual, for NASA believes similar near misses of 30 meter objects occur every two years or so. The unique aspect of 2004FH is that it was actually discovered. Most near-Earth asteroids are never seen.