Obs. : 2009-07-18 Planet Ly alpha (photons/cm^2/sec) Mercury 3.493e+11 Venus 3.501e+11 Earth 3.460e+11 Mars 3.515e+11 Jupiter 3.429e+11 Saturn 3.625e+11 Uranus 3.393e+11 Neptune 3.429e+11 Pluto 3.535e+11