Recordings of Martian earthquakes, or "marsquakes," collected by a robot on the Red Planet may have finally solved a 50-year-old mystery: why one half of Mars is so drastically different from the other.
Since the 1970s, researchers have known that Mars is split into two main areas. The northern lowlands cover around two-thirds of the planet's northern hemisphere, while the southern highlands cover the rest of the planet and have an average elevation roughly 3 miles (5 kilometers) higher than that of the northern lowlands. Mars' crust, which sits on top of a mantle of molten rock similar to the one inside Earth, is also thicker in the southern highlands. This planetary imbalance is known as the "Martian dichotomy."
