Mars's split personality extends to its deep interior, study finds

A new study in Nature reveals that Mars's northern and southern hemispheres differ not just in surface features but also in mantle temperature, with the south being 200–400 degrees Celsius hotter. This thermal anomaly may explain the planet's crustal dichotomy, where the northern plains are low and smooth while the southern highlands are rugged and elevated. The findings have implications for understanding Mars's ancient habitability and geological history.

The study leverages tidal tomography, a technique previously applied to Earth and the Moon, to analyze 16 years of radio tracking data from three Mars orbiters. By measuring how the planet’s gravity field shifts as the sun’s pull varies over its 687-day year, the team detected that Mars’s mantle stiffness differs by over 20 percent between hemispheres. This asymmetry corresponds to a 200–400°C temperature contrast, with the southern mantle running hotter. The findings challenge prior models that assumed a uniform interior, which were based solely on seismic data from the InSight lander in the northern lowlands.

This thermal divide may explain the crustal dichotomy’s origin, potentially linking ancient mantle convection to the formation of the elevated, heavily cratered south and the smoother north. The southern highlands’ hotter mantle could have influenced volcanic activity, water cycling, and surface conditions during Mars’s early habitable period, offering a new lens for interpreting the planet’s geological evolution.