Scientists have found what they believe is the first meteorite from the moon to be discovered on Earth -- a small, glassy rock filled with white fragments, the National Science Foundation announced yesterday.

The finding is significant because scientists have sought evidence for years that meteorites from other bodies in the solar system have been knocked off and sent flying to Earth.

Scientists have only found a dozen or so identifiable meteorites every year, so the total collection from what has fallen on Earth is small. But six years ago, an Antarctic program of the foundation found that meteorites have collected by the hundreds in some Antarctic valleys. Now scientists collect them every summer and recently found rocks apparently cast off Mars. Last summer, geologist William Cassidy found a one-inch cube of greenish stone identified by the Smithsonian Institution with "99 percent" certainty as a moon rock.

"It has been suggested for years that fragments have been knocked off the moon by meteor impact," Cassidy said in a statement. "But this could be the first concrete evidence that such a process actually is occurring."

Most other meteorites found on Earth are believed to have originated in the asteroid belt between Mars and Jupiter.