The Rock by Robert Doherty Page A

leave a hole such as we have here."
    A few students tentatively raised their hands. Pencak pointed her hand at one to reply.
    "A meteorite would have a sufficient amount of kinetic energy that could be transformed into thermal energy upon impact." The student flipped a page in her textbook. "Gifford's table of energy in calories per gram of weight indicate that a meteor moving at ten miles per second would have almost thirty thousand calories of energy per gram."
    Pencak's face lopsidedly twitched in what might have been a smile or a grimace. "True. Very true. And someone tell me the latest theory. How fast was the meteorite traveling that is supposed to have formed this crater?"
    "Uh, twelve miles per second?"
    "Are you answering me or asking me?" Pencak didn't wait. ''Yes. Twelve miles per second, or seven hundred twenty miles per hour. And some number cruncher figured out that the meteor must have been about forty-one meters in diameter at strike and weighed some three hundred thousand tons. The blast would have been the equivalent of five hundred thousand tons of TNT. Quite impressive."
    She paused and surveyed the group. They were scribbling the numbers in their notebooks as if her word were law. "So, if a meteor actually had hit, what else should we find here besides a big hole, fused and pulverized rock, and big boulders thrown miles away?"
    There was a long pause and then a hand went up. "Yes?"
    "There should be some fragments of the meteor."
    "Correct." She waved her hand around the crater. "And have they been found?"
    "Not in any substantial amount," was the reply.
    "So what happened to the material that made up the meteor? What happened to that three hundred thousand tons of nickel and iron? Where is it?"
    Her questions were met with silence. The professor was fidgeting, uncomfortable with her questioning of the class. They were here for information, not intellectual challenge. These young minds were in pursuit of a grade, not knowledge.
    She changed her angle of attack, trying to dredge up some sense of creative thought from the gray mass in front of her. "Can someone tell me what else could have caused this crater? Something that could make such a hole in the earth; fuse quartz sandstone; pulverize solid rock into powder; and not leave a trace fifty thousand years later?"
    A quiet voice ventured something unheard at the back of the group.
    "What was that?" Pencak tried to peer through the gathering dusk at the source of the voice.
    A young man with a scraggly beard stepped forward. "I said a nuclear explosion."
    "Yes. On the order of magnitude of five hundred megatons. Shoemaker in 1963 did something very interesting. I knew him then. Quite a man. He had this marvelous capacity to approach problems in reverse and oftentimes he came up with quite startling results. He studied a crater formed in Yucca Flat, Nevada, by a nuclear explosion and compared it to this crater here. Interestingly enough, he found numerous points of similarity. In fact, they were practically identical, although, of course, they were different in size because of the lower yield of the weapon used in Nevada."
    "But as you said, this was formed approximately fifty thousand years ago," a confident voice from the front of the small crowd noted.
    "Yes, I did," Pencak concurred.
    The speaker grew bolder. "Then it could not have been a nuclear explosion."
    "Why not?"
    The speaker laughed. "Because nuclear weapons weren't invented until 1945."
    "If you mean by man, you are quite correct." Doctor Pencak was about to continue when the professor quickly stepped forward.
    "Thank you very much for a most fascinating day touring the crater, Dr. Pencak. I regret to say that we must be going now in order to make it back to the university on time." With a few muttered thanks from the students the group was gone, trudging over the rim where their bus waited, ready to whisk them back to the academic world where answers were as pat as those that were printed on