When Social Media Lead for NASA's Earth Observatory Adam Voiland noticed a "V"-shaped cloud of smoke in a satellite image one day, he wondered if he could find all 26 letters of the alphabet.
It wasn't an easy task.
"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," Voiland wrote in a post for NASA. "Some letters, like O and C, were easy to find. Others-A, B, and R-were maddeningly difficult."
Eventually he tracked them all down. Here are the letters of the alphabet - a mix of uppercase and lowercase - as seen in stunning satellite images of Earth.
You can also read the original Earth Observatory post here. It includes some pretty great rhyming captions.