There is continuous bombarding of the planets and moons in the solar system by particles thrown away from the sun. There is hardly any effect on Earth apart from the intriguing northern lights particularly because the dense atmospheres and the Earth’s magnetic field protects human beings from the solar wind particles.
However, things are completely different in Moon and on Mercury because there is an erosion of the topmost layer of the rock by the effects of the solar particles.
Recent findings of the TU Wien indicate that the previous models of this process are unfinished. In some cases, the impacts of the solar wind bombardment are drastic than expected. These results are vital for the ESA mission BepiColombo which is the first Mercury mission by Europe. It is possible to find the published findings on planetology journal Icarus.
Prof. Friedrich Aumayr from the Institute of Applied Physics at TU Wien explains that solar wind comprises of charged particles in particular ions of hydrogen and helium. However, other heavier atoms also play a role. The charged particles then hit the surface rocks at a speed of at least 400 to 800 km per second. The impact of the process can produce several other atoms.
Additionally, the particles rise high prior to falling back on the rock surface thus building an “exosphere” around the Mercury or Moon. The exosphere is like a thin atomic atmosphere sputtered by solar wind bombardment from the surface rocks.
The exosphere happens to interest space researchers because its structure enables scientists to identify the chemical composition of the rock surface. It is also easier to assess the exosphere compared to landing a spacecraft on the surface. ESA plans on sending the BepiColombo probe to Mercury in October 2018. That way, they will acquire information concerning the geological and chemical composition in Mercury from the configuration of the exosphere.
However, the whole process calls for an in-depth understanding of the impacts of the solar wind on the rock surfaces and that’s where significant gaps in knowledge emerge. “It is currently assumed that the kinetic energy of the charged particles is responsible for the rock surface atomization,” says Paul Szabo who is a Ph.D. student in Friedrich Aumayr’s team.
Szabo adds that when there is multiple charging of the solar wind particles, there is carrying of a significant amount of energy which is then released in a flash on impact. If such processes are ignored, then that translates to misjudgment of the impacts of solar wind on various rocks. The largest part of the solar wind is protons and was previously thought to have the strongest influence on the rocks.