![[Translate to English:] Gruppenfoto E134-03](data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
The Moon’s surface is continuously bombarded by the solar wind – a stream of electrically charged particles ejected by the Sun. These high-energy ions can knock atoms out of the Moon’s uppermost layer of rock, forming an extremely thin envelope of gas around the Moon known as the exosphere. But how exactly this exosphere forms, has remained a major open question.
A research team at TU Wien, in collaboration with international partners, has now demonstrated that one of the key processes – solar wind–driven sputtering – has been significantly overestimated in previous models. The reason: earlier calculations neglected the rough and porous nature of real lunar regolith. For the first time, high-precision experiments using original samples from NASA’s Apollo 16 mission, combined with state-of-the-art 3D modeling, have allowed the team to determine realistic sputtering rates. The results have now been published in the journal Communications Earth & Environment (Nature Portfolio).
A Thin Atmosphere – But Where Does It Come From?
“The Moon has no dense atmosphere like Earth – but it does have a tenuous exosphere, made up of individual atoms and molecules,” explains Prof. Friedrich Aumayr from the Institute of Applied Physics at TU Wien. “Understanding the origin of these particles remains one of the key questions in lunar science.”
Two mechanisms have been considered as main contributors: either particles are ejected by high-velocity micrometeorite impacts, or they are released via interaction with the solar wind – the constant stream of protons, helium ions, and other charged particles emitted by the Sun. Until now, however, reliable experimental data on actual solar wind sputtering from lunar material has been lacking.
