Intrinsic and Induced Magnetic Fields of the Terrestrial Planets and Their Influence on Atmospheric Escape and Water Inventory

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The general scientific objective of the proposal is the study the influence of the planetary magnetic fields of the terrestrial rocky planets on their atmospheric evolution where solar wind erosion is regarded as most important. The investigations to be performed will address the fundamental question, how efficiently do planetary magnetic fields, intrinsic or induced, shield planetary atmospheres from dehydration? We know already that hydrogen and oxygen are the elements which are extracted most easily from planetary ionospheres. Intriguingly, of all terrestrial planets, the Earth harbors not only the highest amount of water but also has the strongest planetary magnetic field. It is generally thought that the Earth magnetosphere acts as an effective screen, protecting a direct impact and erosive stroke of solar wind on the entire upper atmosphere. Planets which without such a magnetic shielding (as Venus and Mars) might be more exposed to atmospheric erosion. On the other hand, planets with intrinsic magnetospheres interact energetically more strongly with solar wind allowing a focusing of the electro-mechanical energy from solar wind to the auroral zones, where strong electric currents efficiently link planetary and solar wind plasma reservoirs, providing favorable conditions for heating and erosion of the ionosphere. The project will focus on the comparative analysis of loss of ions and neutral atoms from Earth, Venus and Mars based on in–situ measurements on the Mars Express and Venus Express spacecraft complemented by data from satellites orbiting Earth and theoretical and simulation studies.