Max Planck Institute for Solar System Research the clouds and winds of Venus. Microwave instruments determine the composition of atmospheres while infrared spectrometers examine surface rocks. A novel laser altimeter on board BepiColumbo will survey the topography of Mercury to within a meter. Further MPS instruments identify the atoms, electrons, and dust that move around the planets and impact their moons. Here the influence of the solar wind on the atmospheric gases is of particular interest. Theoretical studies and intensive computer simulations help to understand the processes both inside and surrounding the planets and to interpret the measured data. Models developed at MPS can describe, for example,
Water on terrestrial planets of the Solar System primordial ×1.6 SMOW ratio suggests that ~ of has been lost to space via solar wind stripping. The cometary and asteroidal delivery of water to accreting Earth and Mars has significant caveats, even though it is favored by D/H isotopic ratios. Key issues include: An alternative to the cometary and asteroidal delivery of HO would be the accretion via physisorption during the formation of the terrestrial planets in the solar nebula. This would be consistent with the thermodynamic estimate of around two Earth masses of water vapor within 3AU of the solar accretionary disk, which would exceed by a factor