Strange Light Flashes Spotted on Earth From Space Finally Explained

For years, scientists have wondered about the mysterious light flashes that have emenated from Earth.

Famed astronomer Carl Sagan first caught it while looking at images taken by the Galileo spacecraft in 1993, according to a report from Eurekalert. Then, homeward-facing instrument Earth Polychromatic Imaging Camera (EPIC) on NOAA's Deep Space Climate Observatory (DSCOVR) launched in 2015 caught hundreds of these flashes of light reflecting on the Earth in a span of a single year. DSCOVR deputy project scientist at NASA's Goddard Space Flight Center Alexander Marshak first spotted them occasionally flashing over oceans.

Light reflected over water could be easy to explain as sunlight reflecting over a smooth part of a sea or lake. However, the flashes captured by NASA's camera weren't just seen over water bodies.

"We found quite a few very bright flashes over land as well," Marshak said in a statement. "When I first saw it I 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, the scientists considered other sources of water in the Earth system, particularly ice particles in the atmosphere. They analyzed all the sunlight glints over land, 866 bursts in total from June 2015 to August 2016.

What they found was that the flashes detected were limited to spots where the angle between the sun and Earth is the same as the angle between the spacecraft and Earth, so that the spacecraft could be able to pick up the reflected light. This confirmed that sunlight was definitely the source of the mysterious glints.

The scientists also used angles to find that the light reflect off ice particles floating in the air. EPIC, able to measure to the height of clouds, discovered high cirrus clouds where the flashes were located.

"The source of the flashes is definitely not on the ground. It's definitely ice, and most likely solar reflection off of horizontally oriented particles," Marshak said.

The study was published in the journal Geophysical Research Letters.