Saturn in Blue and Gold
影像提供: Cassini Imaging Team, SSI, JPL, ESA, NASA
Explanation:
Why is Saturn partly blue? The above picture of Saturn approximates what a human would see if hovering close to the giant ringed world. The above picture was taken in mid-March by the robot Cassini spacecraft now orbiting Saturn. Here Saturn's majestic rings appear directly only as a thin vertical line. The rings show their complex structure in the dark shadows they create on the image left. Saturn's fountain moon Enceladus, only about 500 kilometers across, is seen as the bump in the plane of the rings. The northern hemisphere of Saturn can appear partly blue for the same reason that Earth's skies can appear blue -- molecules in the cloudless portions of both planet's atmospheres are better at scattering blue light than red. When looking deep into Saturn's clouds, however, the natural gold hue of Saturn's clouds becomes dominant. It is not known why southern Saturn does not show the same blue hue -- one hypothesis holds that clouds are higher there. It is also not known why Saturn's clouds are colored gold.
說明:
為何部份的土星是藍色的？如果人類能漂浮在這顆巨大環系行星附近，所看到的景象會很接近上面這幅影像。這幅影像是三月中旬時，由正繞行土星的卡西尼號探測船所拍攝的。影像中，土星壯麗的土星環只是一道薄薄的垂直線，不過環系在影像左端所投射的暗影，則顯現出它所具有的複雜構造。土星會射出噴泉、大小只有五百公里的衛星土衛二 (Enceladus)，是環系平面上突點。土星的北半球看起來會有些偏藍，和地球藍天的成因完全相同；來自這二個行星無雲區域的雲分子，反射藍光的效率要比反射紅光高。如果我們的視線更深入土星的雲層，將發現土星雲層的主要顏色偏金色。土星南半球為何沒偏藍，其成因仍然未知；假說之一認為此處的雲層較高。此外，土星雲層的色澤為何會是金色的，其原因未明。
資料來源: Scientific American
Department of Physics, NCKU
