The magnetosphere of Mercury, Earth, Jupiter, Saturn, Uranus and Neptune are described.Venus and Mars have no magnetosphere.The solar wind is able to penetrate directly into the atmospheres of these planets.Among them, Mars is the current interest of present book.In absence of Mars own magnetic field, its ionosphere is strongly influenced by solar wind/interplanetary magnetic field.In this book AYS approach, continuity and momentum equations and Steady state Kinetic model are solved. The results obtained from AYS approach and continuity and momentum equations are compared with experimental data measured by MGS/Viking spacecrafts and other calculations carried by MTGCM and Hybrid model.ER measurements carried on 2 April, 1998 by MGS at energy range 10-1000 eV are described in the dayside and nightside Martian atmosphere.The flux, ion production rates, ion and electron densities are calculated due to impact of solar EUV and electron-proton-hydrogen atom with the atmosphere of Mars.A steady state kinetic model is used to calculate parallel electron current density at different potential differences in the exosphere of Mars.