Rosetta's Strangely-Shaped Comet was Created by 2 Separate Cosmic Objects

It turns out that Rosetta's comet may not have always been just one object. Researchers have found that two comets collided at low speed in the early solar system to create the strangely-shaped Comet 67P/Churyumov-Gerasimenko.

The researchers used images in order to identify over 100 teraces seen on the surface of the comet, and parallel layers of material clearly seen in exposed cliff walls and pits. A 3D model was then used to determine the directions in which they were sloping and to visualize how they extend into the subsurface.

"It is clear from the images that both lobes have an outer envelope of material organized in distinct layers, and we think these extend for several hundred meters below the surface," said Matteo Massironi, lead author of the new study, in a news release. "You can imagine the layering a bit like an onion, except in this case we are considering two separate onions of differing size that have grown independently before fusing together."

Layers of materially should form at right angles to the gravity of the object.  Using models, they found that using two separate comets with their own centers of mass would best describe the shape of the current comet.

The findings reveal the true origin of the comet's double-lobed form, which has been a key question since Rosetta first revealed the surprising shape in 2014. This, in particular, may tell scientists a bit more about larger comets, and also shows that comets can fuse together.

For more information about the Rosetta mission, visit ESA's website.

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