Obs. : 2009-02-21 Planet Ly alpha (photons/cm^2/sec) Mercury 3.492e+11 Venus 3.546e+11 Earth 3.460e+11 Mars 3.492e+11 Jupiter 3.492e+11 Saturn 3.453e+11 Uranus 3.566e+11 Neptune 3.561e+11 Pluto 3.438e+11