File:Space Shuttle Atlantis in the sky on July 21, 2011, to its final landing.jpg

English: Like a comet streaking across the atmosphere, the Space Shuttle Atlantis left space for the final time on July 21, 2011, descending to a smooth landing at NASA’s Kennedy Space Centre in Florida. This astronaut photograph, taken from the vantage of the International Space Station (ISS), shows the streak of an ionized plasma plume created by the shuttle’s descent through the atmosphere.

At the time of the image, the ISS was positioned northwest of the Galapagos Islands, while Atlantis was roughly 2,200 kilometers (1,367 miles) to the northeast, off the east coast of the Yucatan Peninsula. The maximum angle of the shuttle’s descent was roughly 20 degrees, though it appears much steeper in the photo because of the oblique viewing angle from ISS. Parts of the space station are visible in the upper right corner of the image.

In the background of the image, airglow hovers over the limb of the Earth. Airglow occurs as atoms and molecules high in the atmosphere (above 80 kilometers, or 50 miles altitude) release energy at night after being excited by sunlight (particularly ultraviolet) during the day. Much of the green glow can be attributed to oxygen molecules.