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Next day, the third foray from the lunar lander Falcon provided more scientific treasures. Returning to a core tube that they had driven deep into the lunar surface and had been unable to extract. Scott and Irwin tried again. "Ready," said Scott as they hauled at the tube, "one . . . two . . . three . . . uhhh." After six minutes of struggle, the tube came out. "Nothing like a little P.T. [physical training] to start out the day," said Scott. His exercises were only beginning. Both men struggled for 20 minutes—uttering at least one audible obscenity—before they could separate the sections of the 8-ft.-long core, which had apparently welded together in the vacuum and searing heat of the moon.
Rille's Origin. Besides revealing much about the moon, the core may provide an intriguing record of the activities of the sun. Has it suddenly flared up during the past few billion years? Have its fires ever diminished? By studying the microscopic tracks left by the bombardment of cosmic rays in each layer of the core, and by looking for traces of an element like argon—which is blown from the sun to the moon in the stream of particles known as the solar wind—scientists may eventually get their answers.
After returning to the rover, Astronauts Scott and Irwin drove to Hadley Rille, a long, winding, 1,200-ft.-deep canyon whose origin has long been the subject of scientific debate. While the rover's remote-controlled TV camera followed them with its big-brotherly eye, the astronauts walked slowly down the rille's gently sloping near side. On the almost vertical far wall, they spotted at least two major layers of material. Even more interesting to the scientists in Houston was the astronauts' report that the second major layer contained at least ten subordinate layers.
Lunar Tumble. To Egyptian-born Geologist Farouk El Baz, who helped train the astronauts, the layering meant that the rille was not created by the collapse of a single lava tube, as some lunar scientists have suggested, but by a number of separate lava flows. Not so, said Astronaut Harrison Schmitt, a professional geologist himself and a member of Apollo 15's back-up crew. He insisted that the rille could just as well have been the result of faulting, or cracking, of the moon's surface as it cooled off.
As Scott and Irwin edged farther down into the rille, Nobel Laureate Harold Urey, watching in Houston, nervously warned: "Don't get too close, fellows." Moments later, catching a foot on a rock, Scott took a headlong tumble and fell clumsily forward on his right arm and shoulder. Not until Scott was helped to his feet by Irwin and continued his jaunt did the world breathe easy. "This time," vowed the unhurt Scott, "I'll look and make sure I don't fall over some silly rock."
A little later, Scott was on his knees again, intentionally. Using a hammer, he chipped a large chunk off a big, lava-like boulder sitting on the rille's ledge. Then he tucked the piece under his arm like a football and galloped enthusiastically back to the rover. Scientists in Houston shared Scott's exuberance. He had apparently snared a valuable chunk of the moon's bedrock.