R. A. Kerr 1989 <p>The 20th anniversary of the first landing on the Moon occurred on July 21, 1989. The vast majority of the Moon rocks collected by the Apollo mission astronauts await further study in the continuing effort to unravel the origin and evolution of Earth's nearest neighbor. Not that the 382-kilogram treasure trove of lunar samples has been gathering dust in the Planetary Materials Laboratory at the Johnson Space Center in Houston. It is just that lunar scientists are being very sparing in their use of the rocks.&nbsp;</p> application/pdf en U.S Geological Survey The Moon; twenty years later article