Astronomy: Cotton Candy Moon

The moon’s visible face has long been mapped, its plains and craters named, its cold curves charted. But as U.S. engineers continue their multibillion dollar effort to get the first man-carrying spacecraft to the moon, U.S. astronomers study the earth’s only natural satellite with steadily increasing intensity. For if its visitors are to survive, science must provide them with lunar information that has so far defied centuries of observation.

Photographs taken through the great telescope at California’s Lick Observatory, and released last week, reveal the moon’s pockmarked crust in astonishing detail (see cut). Forbidding mountains loom above broad valleys and sharply defined crevasses, just as they will appear to approaching astronauts. But for all their clarity, the pictures leave a vital question unanswered. What is the moon actually made of?

Even the finest optical telescope has yet to supply an answer, so Astronomer David D. Cudaback peered beneath the moon’s surface with a vastly different type of instrument. Using the 32 dish-shaped antennas of a Stanford University radio telescope, Dr. Cudaback spent three months measuring the moon’s own electronic transmissions. He traced the variations in the moon’s electrical characteristics, tracked its composition through yards of abstruse equations and decided that its outer surface is just barely denser than the empty space around it.

The moon, says Astronomer Cudaback, is probably covered by a thick porous layer that is as light and airy as finespun cotton candy. It is also possible, he says, that there is a foamy crust of crumbly, crackerjack-like material or a lunar honeycomb with cells intact and filled with gas. The moon got that way, he figures, because it has been bombarded with meteors for billions of years. Striking the moon’s skin with enough energy to melt 100 times their own mass, the meteors liquefied rock or whatever else they hit, splashing gobs of molten material all over the lunar landscape.

Dr. Cudaback’s theory may well supply important information for tomorrow’s astronauts, but it also intensifies their problems. The moon’s frothy covering is sure to complicate the landing technique of any incoming spaceship.