These bodies of ice and dust a few kilometres across are believed to contain primordial material, preserved since the formation of the solar system in the deep - freeze of space. (newscientist.com)
However it affects the planet, the comet should give scientists their closest view yet of a near - pristine visitor from the outer edges of our solar system. (sciencemag.org)
This would be true whether it caught the comet on the way in or on the way out of the solar system. (newscientist.com)