The surface of the Earth and that of Mars, like that of the other terrestrial planets, consists mostly of rock and metals. Despite their apparently unchanging appearance, the crust of these planets is subject to a number of deformations. But compared to the Earth's mantle, the Martian mantle is much more resistant: the Department of Mechanical and Aerospace Engineering of Sapienza University of Rome contributed to this discovery, recently published in Nature. The scientists started by studying Mars' north pole to understand how the planet's surface responds to the pressure exerted by a vast ice cap, documenting post-glacial isostasy processes for the first time on the planet.

The polar cap of Mars, with a thickness of about 3 km and a relatively young age, deforms the Martian crust in a similar way to what is observed on Earth, where the crust gradually rises after the melting of ice caps. This process, known as glacial isostatic adjustment, has been studied on Earth to estimate the viscosity and structure of the mantle. The application of this method to Mars hve posed a significant challenge due to the limited availability of data.

While on Earth one can exploit seismometers distributed in a complex network to accurately monitor the crustal response to glacial loading, on Mars the opportunities for observation are much more limited. To date, only one seismometer has been positioned on the red planet, on board the InSight mission. To overcome this difficulty, the research team combined measurements from the seismometer with the analysis of temporal variations of gravitational anomalies on Mars. In addition, thermal evolution models were added, which together provided fundamental information on the deformation of the Martian crust, and thus on the characteristics of the internal structure.

“Thanks to this combined approach, it was possible to measure the rate of deformation of the Martian crust, which is extremely slow, ‘’ says Antonio Genova of Sapienza University of Rome. “Our estimates indicate that the north pole of Mars is currently deforming at a maximum rate of 0.13 millimetres per year, a value that reflects the viscosity of the upper mantle, which is between ten and a hundred times that of the Earth. This implies that the interior of Mars is extremely cold and resistant to deformation”.

The study provides important information on the internal structure of Mars, a planet that may offer further clues on the evolution of rocky planets, including Earth. In addition, the results indicate that the Martian polar cap, with an age estimated in this study at between 2 and 12 million years, is significantly younger than other large structures on the planet's surface. This discovery opens up new perspectives for future space missions, such as Oracle, proposed and conceived by the Sapienza group, and MaQuIs, which could deepen our understanding of the planet's geological history, its climatic past and its potential habitability.

References:

Broquet, A., Plesa, AC., Klemann, V. et al. Glacial isostatic adjustment reveals Mars’s interior viscosity structure. Nature (2025). https://doi.org/10.1038/s41586-024-08565-9

Info:

Antonio Genova

Department of Mechanical and Aerospace Engineering

antonio.genova@uniroma1.it