Researchers have uncovered a major temperature imbalance deep inside Mars, revealing that the planet’s southern interior is significantly hotter than its northern half. According to gravity measurements, the interior beneath the southern hemisphere is roughly 200 to 400 degrees Celsius (or about 400 to 750 degrees Fahrenheit) warmer than the north and may be partially molten, as detailed in Caltech reporting on a study published in the journal Nature.
Discovery of a Massive Thermal Asymmetry Deep Inside Mars
Lead author and University of Arizona planetary scientist Alexander Berne noted that scientists typically assume planetary interiors are spherically symmetric, which is not necessarily the case. He added that these inferences provide a blueprint for future mission design and scientific exploration.
Connecting Surface Differences to Hidden Interior Heat
On the surface, Mars has long exhibited a stark geologic contrast between its two halves. The southern surface features tall mountains, towering highlands, and heavily cratered terrain, while the northern hemisphere is dominated by broad, low-lying, flat plains. The new gravity data demonstrates that this profound dichotomy extends far beneath the surface.
This hidden heat may help explain several longstanding puzzles regarding the Red Planet. Scientists have previously detected unusual magnetic signatures in iron-rich minerals in the south. A hotter southern mantle could indicate that Mars once possessed a strong enough magnetic field to create distinct magnetic differences between the hemispheres. Additionally, NASA’s InSight mission previously found that seismic waves dissipate more quickly in the south, an observation that aligns with a hotter region.
Co-author and Caltech postdoctoral scholar Amirhossein Bagheri, who is also a former member of the InSight team, pointed out the broader implications for the planet’s history. The dichotomy that we see between north and south is important to understand because it gives information about processes that may have influenced the hydrology of Mars, including the formation of basins that may have held water,
Bagheri said, according to Caltech.
Hypotheses Behind the Southern Thermal Anomaly
Researchers have not yet determined the exact cause of the thermal anomaly, and several hypotheses remain under consideration within the scientific community. One primary hypothesis suggests that a giant impact released heat from the north. A second proposes that spontaneous convection may once have occurred within the southern Martian mantle. A third possibility is that thick geological structures and crust in the south trapped excess heat and prevented it from escaping efficiently over billions of years.
The origin of the anomaly remains an ongoing question in planetary science. As co-author and Brown University planetary scientist Nick Wagner noted, the study does not answer every question, but it adds another line of evidence to help researchers figure out what is occurring beneath the Martian surface.
Research Collaborators and Institutional Support
The study was funded by NASA and involves a broad international team of scientists. In addition to Berne and Bagheri, the paper’s co-authors include:
- Nicholas Wagner and Harriet Lau of Brown University
- Isamu Matsuyama and Angela Marusiak of the University of Arizona
- Sander Goossens of NASA Goddard Space Flight Center
- Karwai Cheng of the Institute of Astronomy and Astrophysics at Academia Sinica in Taiwan
- Antonio Genova of the University of Rome in Italy
- Marc Rovira-Navarro of the Delft University of Technology in the Netherlands
- Chuan Qin of UCLA
- Douglas Hemingway of the University of Texas at Austin
- Shijie Zhong of the University of Colorado Boulder
- Francis Nimmo of UC Santa Cruz
