Rocky exoplanets are expected to be eroded by space weather in a similar way as in the solar system. In particular, Mercury is one of the dramatically eroded planets whose material continuously escapes into its exosphere and further into space. This escape can be traced by atoms such as sodium and helium, scattering sunlight. Due to solar wind impact, micrometeorite impacts, photo-stimulated desorption and thermal desorption, atoms are released from surface regolith. Some of these released atoms are escaping from Mercury's gravitational-sphere. They are dragged anti-Sun-ward and form a tail structure.
We have simulated space weathering of Mercury by escaping sodium atoms (Yoneda et al. 2017) and helium atoms (Yoneda et al. 2021). The Mercury exosphere in the optical Na I doublet was previously detected in ground-based observations, while in the ultra-violet He I line it may be detected with space missions. The escape of helium atoms from Mercury was found to be sensitive to the solar helium line profile, and this can be verified with space data.
We expect similar phenomena on exoplanets. For example, the hot super-Earth 61 Vir b orbiting a G3V star at only 0.05 AU may show a similar structure. Because of its small separation from the star, the sodium release mechanisms may be working more efficiently on hot super-Earths than on Mercury, although the strong gravitational force of Earth-sized or even more massive planets may be keeping sodium atoms from escaping from the planet. For 61 Vir b, we found (Yoneda et al. 2017) that sodium atoms can escape from this exoplanet due to stellar wind sputtering and micrometeorite impacts to form a sodium tail. However, in contrast to Mercury, the tail on this hot super-Earth is strongly aligned with the anti-starward direction because of higher light pressure. An exo-base atmosphere on 61 Vir b seems similar to that of Mercury.