Mercury connections: The surface, space and atmosphere

Category: Cover Story

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In 2022, the Planetary Science Institute hosted a virtual workshop titled “Mercury’s Surface Response to the Interplanetary Environment: Identifying Needed Studies in Laboratory Astrophysics.”

From the workshop, participants generated four review papers to guide future laboratory studies in preparation for BepiColombo, an international mission undertaken by the European Space Agency and the Japan Aerospace Exploration Agency. It is comprised of two spacecraft launched together to Mercury. There, they will orbit and study the complex system that makes up the innermost planet of our Solar System. BepiColombo is only the third mission to explore Mercury. The spacecraft are expected to arrive and enter orbit at Mercury in November 2026.

Read about the first two review papers here.

The third review paper, titled “The interplay of surface composition, mineralogy, and physical conditions that affect the surface release processes and particle environment of Mercury” was also published in Planetary Science Journal and led by Peter Wurz of the University of Bern in Switzerland.

The authors of this review, including PSI Senior Scientist and workshop co-convener Deborah Domingue, aim to examine the intimate connections between Mercury’s surface, the surrounding space environment and its extremely tenuous atmosphere, called an exosphere.

“Mercury is a complex system, where the generation and maintenance of the exosphere is connected to the composition and processing of the surface by multiple processes – including micrometeoroid bombardment, solar wind radiation and solar heating – collectively known as space weathering,” Domingue said.

“We pay attention to the depths to which these interactions affect the surface and discuss the measurements used to diagnose these interactions as well as examine the role the exosphere plays in distributing material over the surface,” Wurz said.

The goal of these review papers is to provide a snapshot of what is currently understood about the production of the exosphere, the modification of the surface and how these are interconnected. Mirroring the focus of the workshop, the purpose of this review is to provide guidance on the gaps in knowledge and where laboratory and theoretical studies can be used to fill those gaps, thus laying the groundwork for in-depth analyses of the anticipated data return from BepiColombo.

This diagram provides a schematic of the processes involved in forming and altering the rocky material, called regolith, of a planetary surface. The processes depicted involve interactions with electrons and ions – atoms with electric charge – in the solar wind (Sputtering, Electron Stimulated Desorption, Surface Implantation), photons heating the surface from the Sun (Thermal Desorption, Photon Stimulated Desorption, Thermo-mechanical Fracturing), and impacts from both large and small meteoroids. Credit: Deborah Domingue/PSI.