Comets are made of dirty ice, and as they approach the Sun and heat up, they emit gas and dust, forming gas and dust tails.
(Comets; are made; of dirty ice) (they; approach; the Sun and heat up) (they; emit; gas and dust) Context(they emit,List([72, 81))):(they; emit gas and dust forming; gas and dust tails)
they emit,List([72, 81))
Comets they they they
are made approach emit emit gas and dust forming
of dirty ice
the Sun and heat up
gas and dust
gas and dust tails