Earth Observations taken by the Expedition 23 Crew

ISS023-E-057948 (25 May 2010) --- A sunset on the Indian Ocean is featured in this image photographed by an Expedition 23 crew member on the International Space Station (ISS). The image presents an edge-on, or limb view, of Earth’s atmosphere as seen from orbit. The Earth’s curvature is visible along the horizon line, or limb, that extends across the image from center left to lower right. Above the darkened surface of Earth, a brilliant sequence of colors roughly denotes several layers of the atmosphere. Deep oranges and yellows are visible in the troposphere that extends from Earth’s surface to 6-20 kilometers high. This layer contains over 80 percent of the mass of the atmosphere and almost all of the water vapor, clouds, and precipitation – several dark cloud layers are visible within this layer. Variations in the colors are due mainly to varying concentrations of either clouds or aerosols (airborne particles or droplets). The pink to white region above the clouds appears to be the stratosphere; this atmospheric layer generally has little or no clouds and extends up to approximately 50 kilometers above Earth’s surface. Above the stratosphere blue layers mark the upper atmosphere (including the mesosphere, thermosphere, ionosphere, and exosphere) as it gradually fades into the blackness of outer space. The ISS was located over the southern Indian Ocean when this image was taken, with the observer looking towards the west. Crew members aboard the space station see 16 sunrises and sunsets per day due to their high orbital velocity (greater than 28,000 kilometers per hour). The multiple chances for photography are fortunate, as at that speed each sunrise/sunset event only lasts a few seconds.