Apparently, “high-altitude, horizontally oriented ice crystals” cause the bright flashes of light, though the phenomenon isn’t all that new. Famous astronomer Carl Sagan first noticed unusual flashes back in 1993, thanks to images taken by the Galileo spacecraft. Previously, Sagan and his colleagues assumed most flashes were caused by smooth pools of water beaming back light directly at the spacecraft’s cameras. But what they didn’t notice were the flashes beaming from large spans of land as well, which required a more refined explanation.
DSCOVR deputy project scientist Alexander Marshak told NASA that when he and his team first saw the flashes, he “thought maybe there was some water there, or a lake the sun reflects off of. But the glint is pretty big, so it wasn’t that.” Instead of looking for water down below, Marshak and his team looked to the sky and realized it was the tiny particles of ice in the Earth’s atmosphere beaming back light. After running several experiments to prove their hypothesis, Marshak’s team published their findings in the journal Geophysical Research Letters.
In total, EPIC recorded 866 glints of light between June 2015 and August 2016. They eliminated the ones caused by reflected sunlight by looking at specific angles of light and used DSCOVR’s measuring instruments to deduce the land-based glints came from cirrus clouds floating high in the sky. “The source of the flashes is definitely not on the ground,” Marshak told NASA. “It’s definitely ice, and most likely solar reflection off of horizontally oriented particles.” NASA scientists will use this information to further investigate how heat and light leaves and enters our atmosphere.
To see the daily archive of EPIC pictures (and possibly discover something new for yourself) head to NASA’s website.