Mapping the Martian Interior Heat
Mars remains a cold and dry planet today, but history tells a different story. Billions of years ago, the planet hosted active volcanoes, a protective magnetic field, and liquid surface water. Its small size caused the interior to cool much faster than Earth, leading to the atmospheric loss seen today. Scientists have long sought to map exactly how that heat is distributed beneath the surface.
A team of researchers recently analyzed archival data from NASA’s Mars Global Surveyor, Mars Odyssey, and the Mars Reconnaissance Orbiter to construct a model of current interior temperatures. By studying subtle changes in spacecraft velocities, they applied tidal tomography to map the gravitational pull and heat distribution of the planet. This effort highlights the disparity between the two hemispheres.
Disparity in Planetary Temperature
The study shows that the southern hemisphere’s interior is 200 to 400 degrees Celsius hotter than the northern hemisphere. This finding aligns with data collected by the now-retired NASA InSight lander, which recorded seismic waves moving through the southern interior at different rates than those in the north. The waves dissipated faster in the south, suggesting a warmer, less rigid composition.
Dr. Alexander Berne, the lead author from the University of Arizona, noted that researchers often assume planetary interiors are spherically symmetric. The new data confirms this is not the case for Mars. As more gravity data becomes available, scientists can better define these three-dimensional structures. This provides a roadmap for planning future missions to the surface.
Insulation and Hemispheric History
The reason for this temperature split relates to the crustal thickness and history of the Martian landscape. The southern hemisphere is dominated by high-altitude terrain, often referred to as the southern highlands. Researchers believe this thick crust acts as an insulator, trapping heat inside the planet for billions of years while the northern lowlands cooled more rapidly.
This pattern stands out against the northern lowlands, which consist of flat plains where water presumably flowed in the distant past. The Hellas basin serves as a notable exception to this pattern, as it sits as a deep impact crater within the southern region. These findings force a reassessment of how scientists categorize planetary cooling cycles.
Future exploration will rely on these models to identify prime landing sites. Understanding how the planet cooled over time provides context for why its climate collapsed. Researchers continue to look at gravitational models to fill gaps left by surface-level missions. Each new data point refines the current understanding of the planetary evolution that turned a once-active world into the barren landscape observed today.