Comparative analysis of plasma environment at Venus and Mars - Venus Express and Mars Express observations and simulations

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The general scientific objective of the proposal is the investigation of the interaction of the Venus atmosphere and ionosphere with the interplanetary medium. The study will be based on observations made by the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) and magnetometer (MAG) experiments on Venus Express (VEX). It will be augmented by a comparison with the situation at Mars, made possible by the successful operation of ASPERA-3 on MEX. This comparative study of the two unmagnetized planets, which induce the magnetospheres around them, is a unique opportunity since almost identical plasma and energetic neutral atom packages (ASPERA-3 and 4) are exploring near-Mars and near-Venus space at the same epoch. The investigations to be performed will address the fundamental question how do strongly the solar wind and the electromagnetic fields affect the planetary atmospheres. The global objective of the proposed investigation is to provide a coherent picture how energy is transferred from the solar wind to surrounding regions of the unmagnetized planets with ionospheric/atmospheric shells and to clarify its environmental effects on the planetary atmospheres. The final product of the research will be a physical model of the escape of the planetary atmosphere, which synthesizes theory, observations and simulations.