|Apollo 15 Astronaut Dave Scott is using his new lunar surface drill. He is planning on drilling two holes, each 10 feet deep to be used in an experiment that will measure the rate of heat flow from the interior of the Moon. Knowledge of this heat flow rate may allow scientists to understand why we see evidence of volcanos on the Moon, yet we see no volcanic activity.
Dave had some difficulty. "When I got the first two borestems in, it was apparent I was hitting something very hard. The first three feet or so was quite easy to drill, and then it was difficult to get it in any further. We'd never seen this in training nor had we ever seen any material that was compacted as hard as this material." Although Dave could not drill either hole to the planned 10-foot depth, the holes were deep enough to allow him to partially insert the temperature sensors.
Results from this experiment indicated that the heat generated in the interior of the Moon is about one-fourth that produced by our planet Earth. This is completely consistent with our observation that there was abundant volcanic activity during the early formation of the Moon, some 3 to 4.5 billion years ago but, as the radioactive elements decayed and the Moon cooled to its present level, there is no longer enough heat to create volcanic eruptions. This is unfortunate for us earthlings. Wouldn't it be exciting to look up at night and see the bright fires and dark smoke plumes of active volcanos scattered across the Moon?