A continent-like shelf beneath the Martian surface hints that a vast ocean once covered up to a third of Mars, reshaping the long-running debate over its watery past.
This artist’s impression shows how Mars may have looked about 4 billion…

A continent-like shelf beneath the Martian surface hints that a vast ocean once covered up to a third of Mars, reshaping the long-running debate over its watery past.
This artist’s impression shows how Mars may have looked about 4 billion…