Mercury appears simple at first glance: a barren, cratered rock enduring extreme temperature swings, lacking moons or atmosphere, and tightly bound to the Sun. Yet its surface chemistry tells a deeply contradictory story. The planet retains volatile elements like sulfur, potassium, and phosphorus, materials that should have vaporized if it had formed in its current scorching orbit. This episode examines the forensic geological evidence that suggests Mercury was born much farther away in a milder region of the early solar system before migrating inward.

Understanding how a planet moves from one orbit to another requires looking at the chaotic dynamics of the young solar system. The episode explores the mechanisms of planetary migration, including the slow drag of the protoplanetary gas and dust disk, as well as violent gravitational scatteri ...