... Tonight's Sky . ... Mercury . ... Mercury may have harbored an ancient magma ocean . Massive lava flows may have given rise to two distinct rock types on Mercuryт??s surface. ... Now, drawing upon the chemical composition of rock features on the planetт??s surface, scientists at the Massachusetts Institute of Technology (MIT) in Cambridge have proposed that Mercury may have harbored a large, roiling ocean of magma early in its history, shortly after its formation about 4.5 billion years ago. ...