Researchers have discovered evidence of a thermal anomaly deep within the mantle of Mars’ southern hemisphere, which may be 200 to 400°C warmer than the rest of the planet. This temperature difference could be linked to processes like regional mantle convection or thermal insulation caused by the thick crust of the southern highlands, which has remained largely unchanged for billions of years. Mars is known for its stark geological differences, with the northern hemisphere consisting mostly of low, flat plains, while the southern hemisphere is higher, more rugged, and filled with craters. These differences are also reflected in the crust’s thickness, magnetization, and how seismic waves travel through the planet. The northern plains of Mars may have once held liquid water on its surface, though such bodies of water may have since vanished. Understanding the origin of these crustal differences could provide important clues about Mars’ ancient water systems and the conditions that might have supported life. The cause of this dichotomy has long been debated, but a recent study published in Nature offers new insights by examining how Mars’ gravitational field changes in response to tidal forces from the Sun. Mars’ orbit around the Sun is slightly elliptical, and its rotation axis is tilted, leading to seasonal tidal forces. These forces cause small deformations in the planet’s shape and internal structure, which in turn affect its gravitational field. By analyzing data from orbiters over nearly 16 years, researchers were able to measure these gravitational changes and infer how the planet deforms under tidal stress. Their findings suggest that the southern hemisphere is about 20% less rigid than the northern hemisphere, which could be due to the significant temperature difference between the two regions. While the data support a temperature difference of 200 to 400°C, the question of whether this difference is a cause or a consequence of Mars’ evolution remains unresolved. Some scientists propose that the dichotomy could have been caused by a massive impact in the northern hemisphere early in the planet’s history, which might have altered the mantle. Others suggest that the southern hemisphere’s thicker crust may have insulated its mantle, keeping it warmer over time. Further research is needed to determine which explanation best fits the available evidence.