Cosmic Ray and UV Radiation Models on the Ancient Martian Surface

摘要: Abstract The atmospheric evolution on Mars is influenced by nonthermal loss processes of heavy constituents. Since does not have an appreciable intrinsic magnetic field at present and a comparatively small gravitational acceleration, all known can be active several important constituents are lost to space. escape rates including water from indicate that the red planet could atmosphere least 1 bar space during past 3.5 Gyr. We investigated with theoretical model flux cosmic-ray-induced particles martian surface solving Boltzmann equations governing propagation protons, neutrons, muons, pions in 7-mbar 1-bar CO 2 atmospheres. found that, present, thin able protect cosmic radiation most incoming protons neutrons impact ground energy fluxes about 6000 1400 MeV cm −2 s −1 , respectively. On other hand, much denser ancient attenuated only secondary particles, mainly were reach 100 while negligible. also evaluated influence magnitude charged no effect, even if one assumes Earth-type Mars, as suggested recent Global Surveyor magnetometer data. In addition we shielding ultraviolet (UV) dense early additional absorption effects O 3 Rayleigh scattering. This gradually becomes transparent UV above wavelengths 220 nm.