Obs. : 2009-09-18 Planet Ly alpha (photons/cm^2/sec) Mercury 3.458e+11 Venus 3.352e+11 Earth 3.472e+11 Mars 3.377e+11 Jupiter 3.512e+11 Saturn 3.361e+11 Uranus 3.454e+11 Neptune 3.512e+11 Pluto 3.621e+11