At http://phys.org/print393164363.html … we learn that comets and meteors rotate and it seems this is one of the reasons why they break up so quickly and yet continue to orbit as a block of smaller objects. The break up is rapid and aided and abetted by the presence of water ice (and other gas ices) in comets, which has been standard theory for some time, due, it is thought, to melt by sunshine (or getting too close to the Sun). NASAs Hubble Space Telescope captured this happening when a comet (a sun grazer) got too close to the sun on one of its orbits through the inner solar system (in January 2016). Some 25 pieces of the comet were seen to drift apart, creating a company of smaller objects on the same general orbit. They even found evidence the comet had broken up to some extent during an earlier passage around the sun and the pieces of that encounter were still orbiting close to each other. In fact, the comet will continue to make passes around the sun for a number of occasions to come.
It it noticeable that old theories about comets still persist and dominate completely the interpretations of the images beamed back to earth. We are told that comets originate in the Kuiper Belt and that it is heat from the sun that causes their volatile behaviour. See Astrophyscal Journal Letters (September 2016).