Risingbd Desk: In the course of just one year, a spacecraft observing Earth spotted hundreds of mysterious ‘flashes’ reflecting off the surface of our planet.
The bizarre phenomenon can be traced all the way back to the 1990s, when astronomer Carl Sagan made note of similar strange ‘glints’ in images from the Galileo spacecraft.
While it was first thought that these strange flashes of light only appeared over oceans, possibly simplifying their origin, scientists have now discovered that they can be seen over land as well.
In a new investigation, researchers found that these bursts likely have a surprisingly small source – tiny, horizontal ice crystals floating high in the sky.
NASA’s Earth Polychromatic Imaging Camera (EPIC) aboard the NOAA’s Deep Space Climate Observatory (DSCOVR) spotted 866 bursts of light over land between the observatory’s launch in 2015 and August 2016.
The flashes seen over the ocean may simply be the reflection of sunlight off a smooth part of an ocean or lake, Alexander Marshak, DSCOVR deputy project scientist, explains.
But, the same couldn’t be said for the flashes seen over land.
‘We found quite a few very bright flashes over land as well,’ said Marshak.
‘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.’
EPIC captures red, green, and blue images several images apart, causing the flashes to appear as tri-coloured specks.
If these strange phenomena were caused by reflected sunlight, the researchers suspected they would be concentrated to distinct locations on Earth, where the angle between the sun and Earth is the same as that between the spacecraft and Earth.
According to the researchers, this also helped to weed out lightning as a possible cause.
‘Lightning doesn’t care about the sun and EPIC’s location,’ Marshak said.
In the study, the researchers hypothesized that the bursts of light may be caused by water high up in the atmosphere, in the form of ice particles.
To find out, they plotted the angles of the reflections, and tapped into two channels on EPIC that allowed them to measure the height of clouds.
The analysis revealed the presence of high cirrus clouds, 3 to 5 miles (5 to 8 kilometers) where these mysterious flashes were seen.
And, the angles suggest they are positioned horizontally.
‘The source of the flashes is definitely not on the ground,’ said Marshak.
‘It’s definitely ice, and most likely solar reflection off of horizontally oriented particles.’
The researchers are using this information to help determine whether or not they have an impact on the amount of sunlight that passes through the atmosphere.
In addition to the implications for Earth, scientists say glints such as those spotted by DSCOVR could even be used to study exoplanets.
Risingbd/May 16, 2017/Mukul