SPOTTING MYSTERIOUS TWINKLES ON EARTH FROM A MILLION MILES AWAY
When we look up at the night sky, we see twinkling stars. When a satellite orbiting a million miles away looks down upon Earth, it sees twinkles, too.
For years NASA scientists, including renowned astronomer Carl Sagan, wondered what the mysterious glints of light appearing on satellite images were. Now, a team of researchers thinks it has uncovered what causes the unexpected flashes.
“These glints are from ice crystals,” said Alexander Marshak, a research scientist at NASA’s Goddard Space Flight Center in Maryland and the lead author of a study published May 15 in Geophysical Research Letters. When oriented just right, he said, the tiny ice particles floating high within clouds reflect sunlight in dazzling fashion. And our ability to spot them on Earth could one day help us study the atmospheres of planets that orbit distant stars.
Marshak is the deputy project scientist for the Deep Space Climate Observatory satellite, or DSCOVR, which is operated by the National Oceanic and Atmospheric Administration. The satellite, which was launched in June 2015, uses instruments that study the sun and also some focused on Earth, which helps with studies of the planet’s climate and how it is changing. A Trump administration budget blueprint for NASA proposed discontinuing its Earth-focused instruments.
Many people who viewed the images posted by NASA noticed the bright flashes and wrote to Marshak asking what they were.
Marshak began to investigate, and he came across early observations of the lights described by Sagan and colleagues in 1993. They had seen the mirrorlike reflections in satellite images taken by the Galileo spacecraft as it swung around Earth en route to Jupiter.
“He saw many, many sun glints, and he mentioned it only over the oceans,” Marshak said. The explanation offered for the flashes was that they were reflections from the smooth surface of the water. But when Marshak reviewed the images from Galileo, he saw the flashes also appeared over land, as they did in the images from DSCOVR.