Reiner Gamma, a mysterious formation on the surface of the moon that has been compared to a "swirl of cream in a mug of hot chocolate," has long been associated with elevated magnetic fields, but a new study led by postdoctoral earth and planetary science research fellow Douglas Hemingway indicates there's a deeper, volcanic source. Using mathematical models of the geologic features, the researchers found that there were narrow magnetic objects associated with the swirls, and they match the shapes of lava tubes and dikes. The study dovetails with another study published last year, which found that the moon's magnetic field lasted more than 1 billion years longer than previously thought. That means that the lava tubes and dikes could have become very magnetic as they cooled. For more on this, see our press release at Berkeley News.