Obs. : 2008-04-17 Planet Ly alpha (photons/cm^2/sec) Mercury 3.627e+11 Venus 3.515e+11 Earth 3.483e+11 Mars 3.647e+11 Jupiter 3.287e+11 Saturn 3.569e+11 Uranus 3.385e+11 Neptune 3.305e+11 Pluto 3.300e+11