Based on the author's own work and results obtained by international
teams he coordinated, this SpringerBrief offers a concise discussion of
the origin and early evolution of atmospheres of terrestrial planets
during the active phase of their host stars, as well as of the
environmental conditions which are necessary in order for planets like
the Earth to obtain N_2-rich atmospheres. Possible thermal and
non-thermal atmospheric escape processes are discussed in a comparative
way between the planets in the Solar System and exoplanets. Lastly, a
hypothesis for how to test and study the discussed atmosphere evolution
theories using future UV transit observations of terrestrial exoplanets
within the orbits of dwarf stars is presented.