source:
livescience.com/62394-comet-snow-rosetta-twitter.html

This clip is made up of 25 minutes worth of images from ESA’s Philae lander, and was processed by Twitter user landru79. (Image credit: ESA/landru79)

Look at this amazing GIF. That snowy-looking scene wasn’t captured on Mount Everest, or in some canyon in Antarctica. That’s the view from a lander on the surface of a comet.

Remember Rosetta? That comet-chasing European Space Agency (ESA) probe that deployed (and accidentally bounced) its lander Philae on the surface of Comet 67P? This GIF is made up of images Rosetta beamed back to Earth, which have been freely available online for a while. But it took Twitter user landru79 processing and assembling them into this short, looped clip to reveal the drama they contained.

As several astronomers and casual observers pointed out in the replies to landru79’s original tweet, the “snowstorm” depicted almost certainly isn’t a true snowfall of the sort experienced on Earth and other planets. Instead, there are likely two or three different phenomena creating the snowy effect.

Up close to the camera, dust particles backlit by the sun are likely moving around, mimicking the look of snow on Earth. Cosmic rays may also be creating snow-like artifacts on the images. And those dots in the background, that appear to be falling straight down and disappearing behind the cliff? Those appear to be stars, which look like they’re falling because the comet is rotating as it orbits the sun every 6.5 years.