After decades of theories and attempts to solve the mystery of Death Valley's sailing stones, a trio of scientists has finally caught the process on tape. Their study started years ago, when two of them (a biologist and an engineer) hauled 15 GPS-equipped rocks onto Racetrack Playa, the dry lake where the famous stones are found. It wasn't until 2013, when a planetary scientist made their two-man band a trio, that they hit the jackpot, though. Apparently, it takes a precise combination of water, ice and wind for the rocks to move. First, the water that floods the lake (which happens rarely) should be around three inches deep, so when it freezes, it forms thin, windowpane-like ice sheets beneath the rocks. Then, it should be sunny the day after that in order for the ice to crack, and for 10MPH winds to propel the rocks forward.