The planets and satellites of our system are constantly attacked by particles released by the Sun. On Earth, this is reflected only in the formation of the amazing northern lights, because all living organisms are protected by a dense atmospheric layer and the magnetic field of the planet. But on the Moon and Mercury, everything is different: the upper layer of the rock is gradually collapsing.
New results from the Vienna University of Technology show that previous models of this process were incomplete. The effects of solar wind bombardment in some cases are much sharper than previously thought. These findings are important for the ESA BepiColombo mission - Europe’s first Mercury research.
Exosphere of Destroyed Rock
The solar wind is represented by charged particles. These are mainly ions of hydrogen and helium, but also heavier atoms, like iron, also play an important role. These particles fall into the surface rocks with an acceleration of 400-800 km / s and the impact can push the atoms. Thus, a thin atmosphere of atoms sprayed from surface rocks by the attack of the solar wind is formed around the Moon or Mercury.
Researchers are interested in studying this exosphere, since its composition allows the chemical components of the rock surface to be derived. This is much easier than dropping a spacecraft to the surface. In October 2018, ESA plans to send a BepiColombo probe to Mercury. He must obtain information about the geological and chemical properties of the planet from the composition of the exosphere.
Paul Szabo in the laboratory of the Vienna Technical University
Impact Level
To study it is important to understand exactly how the solar wind affects rocks. Therefore, scientists analyzed the effects of ion bombardment on wollastonite (moonstone). It was previously believed that the kinetic energy of fast particles is primarily responsible for sputtering the surface of rocks. But this is only part of the truth.
It was possible to show that it is the high kinetic charge that plays the main role. That is why the particles can cause much more damage than previously thought. With multiple charges, the particles carry a huge amount of energy that is instantly released at the moment of collision.
Herbert Bieber, Paul Szabo, Friedrich Aumair, Reinhard Stadmayr, Daniel Mayer (from left to right)
Protons make up the largest part of the solar wind, so they were thought to have the strongest influence on rocks. But the main role is played by helium, because it can be charged twice. High-precision measurements were used for the study, and complex computer simulations were performed at the Vienna Scientific Cluster VSC-3.
