A Dig at the Moon

As the sun rose ever so slowly over the lunar Ocean of Storms, the spidery, three-legged newcomer hesitantly extended and flexed its aluminum, accordion-like arm. Then, reassured that the numbing cold of its flight through space had done no harm, it reached down and pressed its steel-tipped claw into the moon's surface, leaving a small dent. Opening its claw, it deliberately gouged a small trench near its feet, curiously watching each movement to determine the nature of the lunar soil. Thus last week Surveyor 3 became the second U.S. spacecraft to achieve a successful lunar soft landing. "We've not only placed man's eyes on the moon in the form" of a TV camera," said Project Manager Benjamin Milwitzky, "but now we've also put his arms and hands there."

By measuring the current drawn by the electric motors that power Surveyor's arm, scientists will be able to determine the strength and compressibility of the moon's surface. Close-up TV pictures of the soil disturbed by the claw will provide additional information about its texture and cohesiveness. In last week's preliminary tests, for example, it took a pressure of 4 lbs. per sq. in. to make a dent 1 1/2 in. deep in the lunar surface. And TV pictures demonstrated that there was little or no crum bling of the trench walls, indicating that the soil was quite cohesive, perhaps like wet sand.

Three Bounces. Surveyor's pictures also showed that the spacecraft was resting on a gentle slope inside a saucer-shaped crater about 150 ft. across and 20 ft. deep. Although the camera could not peek above the crater's rim, it revealed that the crater floor was relatively smooth, pockmarked with some smaller craters and littered with pebbles and a few rocks no larger than a foot across. All in all, it appeared that the area, one of the eight selected as possible targets for the Apollo mission, was level and uncluttered enough to allow the Apollo lunar module to make a safe landing.

Although Surveyor's mission was generally proceeding according to plan, analysis of its telemetry indicated that it had bounced three times (the first time 35 ft.) after its initial impact on the moon--lifted by its vernier rockets, which had failed to shut down. The unexpectedly rough landing occurred, scientists believed, when the approach radar that controls the rockets became confused by the difference in elevation between the crater bottom and its rim. But the rugged spacecraft quickly proved that it had not been unduly shaken up. Shortly after it landed, it looked down and coolly photographed a nearby "footprint" made on the last bounce by one of its own footpads.

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