Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2001 August 21
Explanation: Neptune has spots. The Solar System's outermost gas giant shows a nearly uniform blue hue created by small amounts of methane drifting in a thick atmosphere of nearly colourless hydrogen and helium. Dark spots do appear, however, that are anti-cyclones: large high-pressure systems that swirl in Neptune's cold cloud tops. Two dark spots are visible in the above picture taken by the robot Voyager 2 spacecraft in 1989: an Earth-sized Great Dark Spot located on the far left, and Dark Spot 2 located near bottom. A bright cloud dubbed Scooter accompanies the Great Dark Spot. Recent computer simulations indicate that scooters are methane clouds that might commonly be found near dark spots. Subsequent images of Neptune by the Hubble Space Telescope in 1994 indicated that both of these dark spots had dissipated, but another had been created.
Authors & editors:
Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
& Michigan Tech. U.