Wilbur Hanson Kalb, age 13, of Hatboro, Pennsylvania, for his question:

Is there really vapor on the moon?

Vapor may be gaseous water or any other gas. Though the moon has no dense, earth type atmosphere, gaseous fumes sometimes escape from below the surface. The Apollo 15 astronauts found that the deeper lunar layers gradually grow warmer, much like the earth's    though on a smaller scale. They too are heated by subsurface radioactive materials. We now know that the lunar surface quivers with numerous moonquakes. From time to time these upheavals release buried heat and gaseous vapors.

While the Apollo 15 astronauts were checking these items on the moon, the command ship was busy checking from aloft. One of its instruments was a mass spectrometer on a 20 foot boom. Its purpose was to detect gaseous particles at orbit level. It found a sprinkling of carbon dioxide, various hydrocarbons and good old water vapor. These particles of high lunar vapor proved to be ten times more abundant than those farther out in space, between the earth and the moon.