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Those transmissions were by far the clearest yet sent from the moon. The red, white and blue of the U.S. flag were displayed in brilliant hues on TV screens as the astronauts raised a banner that had hung in Mission Control since the first moon landing of Apollo 11 in July 1969. Expertly operated by technicians at remote control consoles in Houston, the camera picked up the puffs of dust raised by the astronauts as they walked, awkwardly learning to cope with the moon's weak gravity—a sixth that of the earth—and the bulkiness of their space suits. While all the world watched his struggle, Schmitt confessed: "I still haven't learned how to pick up rocks . . . a very embarrassing thing for a geologist to admit."
Cernan also had reason to be embarrassed. With one swing of his geological hammer, he accidentally clobbered the $13,000,000 moon car, knocking off part of one of its rear fiberglass fenders, which act as shields against the spray of dust churned up by the rover's wire mesh wheels. Cernan tried to reattach the section of fender with gaffer tape. But because of the everpresent, clinging fine-grained lunar dust, it would not stick. As precious minutes ticked away. Mission Control suggested that the astronauts abandon the fender repair work and get on with the more important job of setting up the five ALSEP (Apollo Lunar Surface Experiments Package) experiments.
The experiments also posed problems. Cernan worked so hard trying to drill holes for the important heat-flow experiment—which had been inadvertently disconnected on the Apollo 16 mission—that his pulse climbed to 150 beats per minute. NASA doctors, monitoring his heartbeat, ordered him to rest. Coming to Cernan's aid, Schmitt took a dramatic spill as he tried to extract a balky core tube from the ground. All of the experiments were finally set up, but it was learned later that a key instrument—the surface gravimeter—had jammed. It was a bitter disappointment to scientists, who had hoped that the instrument would help determine if gravity waves, originally postulated by Albert Einstein, really exist.
Unaware of that failure, the elated astronauts improvised a duet, singing, "While strolling on the moon one day . . . in the merry month of December." Mission Control soon interjected a sobering note by notifying them that they were already 40 minutes behind their timetable and that the original objective of their first moon ride had to be scrubbed. But a nearer crater provided an intriguing find: vesicular rocks, containing pockets formed by gas. That was one of several clues that the area had once been the scene of volcanic activity.