The extreme X-ray/EUV radiation and the complex plasma interaction of young stars with the upper atmosphere-magnetosphere environment of terrestrial planets and possible large exo-moons within orbits of gas giants within habitable zones will be studied by coupling and developing numerical test-particle and Monte Carlo models. For the first time the production of hydrogen and energetic neutral atoms (ENAs) around early Earth-like planetary bodies with stellar EUV and particle heated and expanded thermospheres during the host star's active stage will be studied. A particular focus on the energy deposition of ENAs and charged particles into to the thermospheres of Earth-like planets within stable orbits around single and binary stars will be considered. Furthermore, the extreme radiation and plasma interaction of young main sequence stars on comets which should have brought organic molecules as well as part of the water to young planets will also be investigated in a comparative way. The subproject is highly interlinked with the other subprojects and its results are very relevant how Earth-like planetary atmospheres as well as that of large exo-moons can evolve where conditions can exist that life like on Earth started.