Taylor said that when a geologist smashes a rock here on Earth, that person will smell some odor that has been generated by the smashing of minerals, thereby creating the so-called dangling bonds. But on the moon, the dangling bonds can exist for a long time, Taylor said. And because lunar rock and soil is roughly 43-percent oxygen, most of these unsatisfied bonds are from oxygen. "In a nut-shell, I believe that the astronauts all smelled unsatisfied dangling bonds on the lunar dust … which were readily satisfied in a second by the lunar module atmosphere, or nose membrane moisture," Taylor told Space.com.