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Comet 67P/Churyumov-Gerasimenko
An image from the Rosetta probe shows the Cliffs of Hathor on Comet 67P/Churyumov-Gerasimenko. Specks and streaks cover the frame. Some of them are dust particles, others are background stars. The star cluster NGC 2362 is prominent near the upper left edge of the picture. (ESA / Rosetta / MPS / OSIRIS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA Image)

It’s been 19 months since the European Space Agency’s Rosetta mission to Comet 67P/Churyumov-Gerasimenko ended, but the probe’s pictures stirred up a fresh flurry of excitement this week.

Or are those snow flurries?

The excitement is over 33 pictures that were snapped back on June 1, 2016, and posted to Rosetta’s online archive last month. The sequence, captured from a distance of several miles over the course of about 25 minutes, shows the comet’s Cliffs of Hathor with boulders strewn about.

One by one, the pictures are interesting enough. But when a Twitter user with the handle Landru79 (a.k.a. Jacint Roger Perez) put them together in a one-second animated GIF, the scene really came to life:

As the point of view moves around the valley, the sharply shadowed ridges and boulders produce an eerie 3-D effect. Bright specks and streaks flash through the image like a snowstorm. Most of those specks are background stars. Other specks may look like snowflakes, but Mark McCaughrean, ESA’s senior adviser for science and exploration, suspects that they’re something else.

“My guess is that this is dust quite close to the spacecraft as it moves by, giving the illusion that it’s ‘snow’ falling on Comet 67P kilometers away in the background,” McCaughrean said in a tweet.

At least some of the streaks may be cosmic-ray hits on the camera’s detectors.

“If we stack the whole set, lining up with the stars in the background, it’s easier to distinguish which are stars and which are dust (forget about cosmic rays),” Landru79 / Perez said in a Spanish-language follow-up tweet. See for yourself:

It’s even possible to determine which stars are in the background. We’re looking in the direction of the constellation Canis Major. McCaughrean and other sharp-eyed observers say the field of view includes the star 27 Canis Majoris and the star clusters NGC 2362 and NGC 2354.

Today the GIF was featured as the Astronomy Picture of the Day, and got a shout-out on Twitter from none other than Elon Musk.

But wait … there’s more.

Perez is continuing to post GIFs based on Rosetta imagery. Here’s a sampling, offered up with confidence that you can figure out how to translate from Spanish if need be:

Thanks, Rosetta — and gracias, Señor Perez!

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