Mars is Lopsided Inside: Southern Mantle is 400°C Hotter and Partially Molten

Have you ever microwaved a frozen Hot Pocket, only to bite into one side that’s liquid magma while the other side is still an iceberg? It turns out the entire planet of Mars has been doing the exact same thing for four billion years.

In a breakthrough study published in Nature, geophysicists from Caltech and the University of Arizona revealed that the Red Planet is profoundly thermally asymmetric. Deep beneath the Martian crust, the southern mantle is between 200°C and 400°C (400°F to 750°F) hotter than the northern mantle—and is likely in a partially molten state.

This discovery instantly solves three of the biggest head-scratchers in Martian planetary science:

• The Martian Dichotomy: For centuries, astronomers wondered why the southern hemisphere is high, rugged, and densely cratered while the northern hemisphere is low, smooth, and flat. The answer: a massive, buoyant upwelling of hot, low-density mantle material buoyed the southern crust upward.
• The Ghostly Magnetic Fields: Ancient magnetized minerals are concentrated heavily in the southern highlands. A hotter, semi-molten southern interior explains why a vigorous ancient dynamo once churned underneath the south, baking magnetic signatures into the rocks.
• Volcanic Megastructures: The lopsided thermal plume fed massive volcanic provinces like Tharsis and Elysium, sustaining geological activity and potentially ancient underground hydrothermal reservoirs far longer than textbook models assumed.

So if future human astronauts ever build retirement colonies on Mars, real estate in the southern hemisphere might just come with free geothermal floor heating!