Jupiter Keychain

Two of the moons were crossing Jupiter's face at the same time as the three shadows. Jupiter appears in pastel colours in this photo because the observation was taken in near-infrared light. Astronomers combined images taken in three near-infrared wavelengths to make this colour image. The photo shows sunlight reflected from Jupiter's clouds. In the near infrared, methane gas in Jupiter's atmosphere limits the penetration of sunlight, which causes clouds to appear in different colours depending on their altitude. Yellow colours indicate high clouds; red colours lower clouds; and blue colours even lower clouds in Jupiter's atmosphere. The green colour near the poles comes from a thin haze very high in the atmosphere. Ganymede's blue colour comes from the absorption of water ice on its surface at longer wavelengths. Io's white colour is from light reflected off bright sulphur compounds on the satellite's surface.