Mars’s Deep Secret: Thermal Anomaly Explains North-South Divide

<>

Mars hides a massive thermal anomaly deep within its southern mantle, where temperatures soar 200 to 400 degrees Celsius hotter than the northern hemisphere. According to a study published in Nature on August 26, 2026, researchers used two decades of spacecraft tracking data to uncover this subterranean heat division.

Decoding the Martian Subsurface via Tidal Tomography

For decades, the stark dichotomy between the northern flat lowlands and the rugged southern highlands of Mars remained a surface-level mystery. Scientists lacked a clear mechanism to explain why the crustal division ran so deep. Direct thermal measurements of the Martian interior were nonexistent. Instead, an analytical technique called tidal tomography cracked open the problem without requiring a single drill bit.

By analyzing nearly 20 years of radiometric tracking data, the team observed how tiny perturbations in the planet's gravitational field responded to the Sun's gravitational pull.

Mars orbits the Sun in a slightly eccentric, non-circular path with a tilted rotational axis. This geometry triggers periodic tidal forces. These forces leave a subtle, measurable fingerprint on the planet’s gravity field. By parsing these variations, the team mapped internal material properties with unprecedented three-dimensional precision.

Unlocking the Thermal Divide Between Northern and Southern Hemispheres

Planetary scientists traditionally assumed planetary interiors were largely symmetrical around their rotational centers. The gravity-field data proved otherwise. The superheated southern mantle zone directly aligns with the planet’s well-documented geological split. The southern crust sits higher and thicker, while plains dominate the north.

The team’s internal models indicate that a thermal differential ranging from 200°C to 400°C drives the variance in mantle rigidity between the two hemispheres, potentially accompanied by minor compositional differences. This temperature spread bridges several long-standing planetary puzzles. Iron-rich rocks in the southern hemisphere preserve signatures of an ancient Martian magnetic field. Meanwhile, data from the InSight lander revealed distinct attenuation patterns in seismic waves traversing southern terrain.

Higher temperatures alter how seismic shear and compressional waves propagate through mantle silicate structures. This thermal mapping directly connects deep interior physics to surface seismic records.

Unresolved Origins of Subterranean Heat

The exact genesis of this persistent thermal pocket remains under investigation. Amir Hossein Bagheri, a postdoctoral researcher at Caltech and a participant in the study, notes that mapping this hemispheric divide clarifies the historical distribution of Martian water, including basins that likely pooled liquid water in the planet’s distant past.

Several hypotheses attempt to account for the excess heat. Researchers point to ancient, long-lived mantle convection currents, insulating effects from a thicker southern crust that trapped primordial heat, or the lingering scars of a massive early impact event. Whether early impact basins or deep plume upwellings triggered the divide, the internal architecture has endured for billions of years.

The 30-Second Verdict on Planetary Tracking

• Methodology: Tidal tomography analyzing 20 years of NASA spacecraft tracking data.
• Core Finding: A 200°C to 400°C thermal anomaly in the southern Martian mantle.
• Broader Impact: Proves that gravity-tracking missions can map inaccessible planetary interiors.

Ultimately, this discovery redefines our understanding of terrestrial planet evolution. As future orbital missions deploy dedicated gravity-mapping instruments, planetary scientists gain a sharper lens to peer beneath the crusts of Mars and other rocky bodies across the solar system.