Image mosaic by Daily Mail.

Image mosaic by Daily Mail.

A few years ago, while working on a story about wildfires, a V appeared to me in a satellite image of a smoke plume over Canada. That image made me wonder: could I track down all 26 letters of the English alphabet using only NASA satellite imagery and astronaut photography?

With the help of readers and colleagues, I started to collect images of ephemeral features like clouds, phytoplankton blooms, and dust clouds that formed shapes reminiscent of letters. Some letters, like O and C, were easy to find. Others—A, B, and R—were maddeningly difficult.

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NASA Earth Observatory, December 2015