Habitability

Earth constitutes the only known example of a habitable planetary body, whose present atmospheric composition is quite different from those of other planets in the solar system, as well as from that existing on Earth billions of years ago. Understanding the evolution of our atmosphere over geological times would allow us to not only open a window into Earth’s history, it also can help determine if, and under what conditions, Earth-like conditions for habitability can exist. There are several main factors that control atmospheric evolution, such as the contribution of particle influx from space (meteors, etc.), biospheric reactions, sub-surface activities (volcanic, bacterial denitrification, etc.), and a net particle escape of atmospheric constituents into space.

Several mechanisms have been invoked to explain planetary atmospheric loss. Due to the size of the Earth’s magnetosphere, there is no direct interaction between the solar wind and the neutral atmosphere, an interaction that can play a key role in escape in non-magnetized planets like Mars. In addition, thermal escape of neutrals from the Earth is limited to only the lightest elements like hydrogen and helium. The 7iPWOM opens the possibility to explore the possible role played by loss of charged particles from Earth’s atmosphere, facilitated via the Earth's ionosphere, the charged particle component of the Earth's upper atmosphere. This ionospheric outflow provides a pathway for atmospheric migration and escape without requiring direct interaction with solar wind particles or high thermal speeds. The solar EUV photon flux striking the upper atmosphere, as well as to the electromagnetic driving from the solar wind, both play a key role in regulating this escape.