Mars Orbiters Detect Thermal Anomaly Beneath Crust

Analysis of tracking data from Mars orbiters has revealed time-variable gravity field behavior that reflects the structure underlying the Martian crustal dichotomy. This behavior indicates the preservation of a significant thermal anomaly, estimated to be between 200 and 400 degrees Celsius, in the present-day mantle located below the planet's southern highlands. The findings, published online on August 26, 2026, in the journal Nature, utilize a technique known as tidal tomography to probe the planet's interior.

Tidal tomography, a method that analyzes the gravitational pull exerted by celestial bodies on a planet, allows scientists to infer subsurface structures. In the case of Mars, the researchers examined subtle variations in the planet's gravity field over time, which are influenced by the distribution of mass beneath the surface. These variations are particularly pronounced in regions associated with the crustal dichotomy, a fundamental geological feature of Mars characterized by a stark contrast between the smoother, younger northern lowlands and the heavily cratered, older southern highlands. The observed gravity field changes suggest a significant difference in density and temperature between these two regions, extending deep into the Martian mantle.

The identified thermal anomaly, ranging from 200 to 400 degrees Celsius, implies that a substantial amount of heat is still being retained beneath the southern highlands. This preserved heat is a crucial piece of evidence for understanding the thermal evolution of Mars. Unlike Earth, which has a geologically active interior driven by ongoing mantle convection, Mars is generally considered to be a much less geologically active planet, with its internal heat largely dissipated over billions of years. The presence of such a significant thermal anomaly suggests that certain regions of the Martian mantle may have cooled at a slower rate than previously assumed, or that there are ongoing processes contributing to heat retention.

This discovery has significant implications for our understanding of Martian geology and its potential for past or present habitability. The southern highlands, with their thicker crust and ancient surface, are thought to represent some of the oldest terrains on Mars. The presence of a persistent thermal anomaly in this region could influence the subsurface environment, potentially affecting the presence and stability of liquid water, a key ingredient for life as we know it. Future research will likely focus on further characterizing the extent and origin of this thermal anomaly, and its potential impact on the planet's geological history and the search for extraterrestrial life. The study's DOI is 10.1038/s41586-026-10893-x.