An elusive "red sprite" flash, photographed by Expedition 31 astronauts aboard the International Space Station on April 30, 2012. The sprite (upper right) appears high above a lightning strike (bright spot in the clouds). Red sprites only last for a few milliseconds, sending pulses of electrical energy up toward the edge of space--the electrically charged layer known as the ionosphere--instead of down to Earth's surface. More about this image on NASA's Earth Observatory.
