Thermal Anomaly Detected Beneath Mars' Southern Hemisphere
Researchers have identified a significant thermal asymmetry beneath Mars’ surface, with the mantle under the southern hemisphere being 200 to 400 degrees Celsius warmer than that beneath the northern hemisphere. This discovery, based on gravitational measurements, suggests that the southern mantle may be partially molten.
The findings were published in Nature on August 26, 2026, in a study led by Alexander Berne. The study utilized data from Mars Global Surveyor, Mars Odyssey, and Mars Reconnaissance Orbiter to analyze seasonal variations in the Martian gravity field. This approach, known as tidal tomography, revealed deviations in the planet's gravity field that indicate a substantial temperature differential.
Concrete findings include gravitational deviations up to 300% in degree-3 coefficients compared to symmetric models, and a variation in the mantle’s shear modulus exceeding 20%. These results are consistent with the detected thermal anomaly beneath the southern highlands.
Possible explanations for this anomaly include thermal insulation by the thick southern crust, regional mantle convection, or iron enrichment in the southern mantle. The implications of these findings extend to Mars’s geologic history, magnetic anomalies, and seismic wave behavior, with faster seismic wave dissipation observed in the warmer southern regions.