A sunset captured last month by astronauts aboard the International Space Station shows the many layers of the Earth's atmosphere. At bottom, is the Earth's surface at night. Above that, appearing in orange and yellow, is the Earth's troposphere, which contains approximately 75 percent of the atmosphere's mass almost all of its clouds. Above the troposphere, seen as a light blue band, is the stratosphere, where jet airliners cruise. Beyond the stratosphere, the atmosphere thins out into the darkness of outer space.