Comet 67P/C-G was formed by a soft collision

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Scientists, using data from Rosetta, have concluded that Comet 67P/C-G’s double lobed shape was caused by the slow-motion collision of two distinct comets.

By using high-resolution images taken between 6 August 2014 and 17 March 2015 to study the layers of material seen all over the nucleus, they have shown that the shape arose from a low-speed collision between two fully fledged, separately formed comets. “It is clear from the images that both lobes have an outer envelope of material organised in distinct layers, and we think these extend for several hundred metres below the surface,” says Matteo Massironi, lead author from the University of Padova, Italy, and an associate scientist of the OSIRIS team. “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.”

While erosion continues to eat away at the comet’s surface, changing its shape, the two lobes formed separately, though in much the same way.


  • J Fincannon

    Ah! This seems unlikely! Given the size of space and the distribution of orbits, its seems HIGHLY unlikely to have a slow speed impact. I would even say its hard to believe two comets could come into any proximity of each other. I want to see the statistical analysis that shows it is possible within the age of the solar system.

  • PeterF

    To do a statistical analysis wouldn’t they need an accurate count of the number, density, and relative motions of cometary bodies within the Oort cloud?
    Perhaps a low speed impact was what ejected it from the Oort cloud in the first place?

    To paraphrase Shrek and Donkey; Comets are like onions. They’re stinky and they make you cry…

  • J Fincannon

    “Oort Cloud”…. what a hypothesis!

    I think the implication of the article was that it happened near the formation of the solar system somewhere in the solar system, but I could not find where this was explicitly stated. I was really giving them the benefit of the doubt by allowing them billions of years to effect this low speed impact. You can make a simulation with a variety of assumptions. I would start with the solar system size at the current hypothesized Oort cloud limit and populate it with millions or billions or trillions of comet sized bodies. Even with trillions,since space is so big, I predict no low speed encounters, although high speed ones are likely over the age of the solar system.

  • hondo

    Use of the word collision may be the confusion. Don’t see any problem with slow speed drifting into each other from sides and rear. Head on is a completely different story.

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