When planetary scientists say the interior of Mars resembles a rocky road brownie more than a piece of buttery shortbread, the tasty metaphor masks billions of years of geological violence. The Red Planet’s mantle is permanently trapped beneath an unmoving outer crust preserving the planet’s insides. As these waves made their way into Mars, InSight flagged sizable interference. While our home planet is far more geologically active, the other rocky planets may resemble Mars beneath their own crusts. “It sealed off the mantle beneath, locking in those ancient chaotic features—like a planetary time capsule.”