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Twins! Rosetta Probe's Comet Has Scientists Seeing Double

Much to scientists' surprise, images from the European Space Agency's Rosetta probe reveal that the comet it's been chasing is actually two comets.

Much to scientists' surprise, the latest imagery from the European Space Agency's Rosetta probe reveals that the comet it's been chasing is actually two comets, seemingly smashed together.

"Wow, wow, wow. I can't wait to get closer!" the Planetary Society's Emily Lakdawalla wrote in a blog post about the pictures.

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The July 11 images show the nucleus of Comet Churyumov-Gerasimenko to be a "contact binary" — a larger and a smaller object locked together, with a total size in the neighborhood of 2 by 2.5 miles (3.5 by 4 kilometers). This animated GIF shows the comet spinning.

Rosetta team member Philippe Lamy, an astronomer at France's Laboratoire d'Astronomie Spatiale, is quoted as saying that Churyumov-Gerasimenko's two parts must have smashed together at a speed of 7 mph (3 meters per second) to stick together the way they do.

Rosetta is supposed to rendezvous with the comet next month and drop a lander called Philae onto its surface in November. Philae navigator Eric Jurado was quoted as saying that Churyumov-Gerasimenko's weird shape could make the landing "more difficult, as this form restricts potential landing zones."

These quotes came from a news release that was issued by France's CNES space agency on Tuesday but was then removed from the Web. (Try checking this cached version of the release.)

On Wednesday, ESA's Rosetta blog said the image release was "unscheduled." New images and a movie will be part of a release "coordinated with all partners involved in the Rosetta mission" on Thursday, according to the blog post. We'll update this item with extra goodies when they're available.

Update for 8:50 p.m. ET July 17: ESA has released additional images of the comet, plus some additional analysis. The comet could have taken on its weird shape when two separate objects were smooshed together. However, it also could have started out as a single, more rounded object that was pulled into its current weird shape by gravitational interactions with, say, Jupiter or the sun. It could have been sculpted by asymmetrical ice evaporation, or by some sort of catastrophic impact.

“We currently see images that suggest a rather complex cometary shape, but there is still a lot that we need to learn before jumping to conclusions," Rosetta mission manager Fred Jansen says in Thursday's ESA posting. Don't miss ESA's animated image, showing what some have called a cosmic "rubber ducky."