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Thin Blue Line | by NASA Earth Observatory
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Thin Blue Line

NASA astronaut Scott Kelly posted this striking photograph of the sun peeking over the thin blue line of Earth's atmosphere to Twitter on September 21, 2015. Since the early days of space flight, astronauts have been drawn to the unique view of the atmosphere that's only available from orbit. “For the first time in my life, I saw the horizon as a curved line. It was accentuated by a thin seam of dark blue light: the atmosphere,” said Ulf Merbold, a German astronaut who flew on Space Shuttle Columbia in 1983. “Obviously, this was not the ‘ocean’ of air I had been told it was so many times in my life. I was terrified by its fragile appearance.”


See Kelly's tweet at


See more astronaut quotes about looking back at Earth at


Read a story about air pollution at

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Uploaded on September 22, 2015