There's Something Molten Under Mars's South Pole
About this episode
This episode discusses a thermal anomaly beneath Mars's south pole, revealing it is significantly hotter and partially molten compared to the northern hemisphere.
Today's episode — S05E183, Wednesday September 2, 2026: Main story: A thermal anomaly beneath Mars's south pole. Writing in Nature on August 27, a team led by Alexander Berne (Caltech PhD '26, now University of Arizona) reports that the interior of Mars's southern hemisphere is 200–400 °C hotter than the northern hemisphere and partially molten. The team used tidal tomography — measuring how much the solid body of Mars flexes under the Sun's tidal pull by tracking minute velocity changes in three orbiters (Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter) across roughly 25 years of radio tracking data. Hotter, softer rock deforms more, so the degree of flex reveals interior temperature. The result offers a deep-interior explanation for the Martian crustal dichotomy — the sharp division between the smooth low northern plains and the ancient, thickly crusted southern highlands, unexplained since the Viking era — and also accounts for the concentration of crustal magnetic anomalies in the south and the unexpectedly strong seismic-wave damping seen by InSight. The cause of the asymmetry remains open: a giant early impact, lopsided mantle convection, or a…
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