Scientists from the University of Bern in Switzerland have proposed a new theory: the Sun may have influenced the formation of rocks and cracks on the surface of Mercury, the planet closest to it. Researchers suggest that tidal forces from the Sun played an important role in this process — similar to those that cause tides on Earth, although much weaker.
This discovery undermines the long-standing hypothesis that Mercury’s surface irregularities were caused solely by the cooling and contraction of its crust.
The inspiration for the new hypothesis was Mercury’s unusual behavior in orbit. The planet moves along a very elongated trajectory and rotates around its axis in a unique way: three rotations around its axis for every two orbits around the Sun. This resonance causes constant “stretching and compression” of the surface, which can leave noticeable marks in the form of cracks, bumps, and rocks.
The team of scientists, including Dr. Liliane M. L. Burkhard and Professor Nicolas Thomas, created a computer model of how tidal forces have affected Mercury over billions of years to test this hypothesis. The results show that although tidal forces do not cause faults, they can determine their direction and location.
This discovery is of great significance for further research on Mercury. By the end of 2026, the BepiColombo spacecraft, developed by the European Space Agency (ESA) in collaboration with the Japan Aerospace Exploration Agency (JAXA), will arrive at the planet. The University of Bern also joined this mission and developed one of the key scientific instruments — BELA, the laser altimeter. This device will create a super-accurate 3D map of Mercury’s surface with an accuracy of up to 10 centimeters.
According to Professor Thomas, such high-precision data will help to better understand how Mercury’s surface has changed over geological time.
“Our discoveries could change ideas about how planets develop,” Liliane M. L. Burkhard is convinced.
The findings of the study are significant not only for the study of Mercury, but may also be indicative of other planets in the Solar System, including Earth.
