Mercury, the smallest planet in the Solar System, has been contracting for billions of years. The cooling of its interior causes a slow contraction that deforms the surface, giving rise to major faults and landforms known as lobate scarps, which extend for hundreds of kilometres and can reach heights of up to 2,000 metres.
A new study, Graphite lubricates Mercury’s global contraction, published in Nature Communications, has identified graphite as a possible key element in this process. The research was carried out by a team from the University of Padua, the Italian National Institute for Astrophysics (INAF-OAPD) and the University of Milano-Bicocca.
Representing the University was Andrea Bistacchi, from the Department of Earth and Environmental Sciences, co-author of the study. The work combined analysis of Mercury’s topography with laboratory friction experiments on rocks similar to those found in the planet’s crust.
The results indicate that graphite-rich layers, present since the earliest stages of Mercury’s history, may have continued to influence the planet’s tectonics up to the present day, facilitating movement along its major faults. Graphite may therefore have acted as a natural “lubricant”, in the absence of the fluids that can promote fault slip on Earth.
The discovery also suggests that Mercury may have contracted more than previously estimated and shows how conditions dating back to the earliest stages of a planet’s formation can continue to influence its surface billions of years later.
The research also opens up new prospects ahead of the ESA/JAXA BepiColombo spacecraft’s insertion into orbit around Mercury, scheduled for next November. The SIMBIO-SYS instrument will be able to contribute to the detailed study of the planet’s major faults by reconstructing their three-dimensional geometry and analysing their mineralogical composition.
To find out more, read the press release and the research published in Nature Communications